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Ep. 02 Chloe Mikles Discusses Bluefin Tuna Science

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Контент предоставлен Katie C. Sawyer. Весь контент подкастов, включая эпизоды, графику и описания подкастов, загружается и предоставляется непосредственно компанией Katie C. Sawyer или ее партнером по платформе подкастов. Если вы считаете, что кто-то использует вашу работу, защищенную авторским правом, без вашего разрешения, вы можете выполнить процедуру, описанную здесь https://ru.player.fm/legal.

In this podcast episode, Katie interviews Chloe Mikles, a PhD student studying bluefin tuna. They discuss Chloe's research on bluefin tuna and blue marlin movement ecology and population structures. Chloe explains the process of tagging fish and the importance of tracking their migration patterns. Katie and Chloe also talk about the bluefin tuna fishery in North Carolina and the international management of bluefin tuna populations around the world. Chloe shares her background and interest in studying bluefin tuna and discusses her PhD work on population differentiation. They also touch on the handling and care of tagged fish and the differences between handling bluefin tuna and billfish. In this conversation, Katie and Chloe discuss the tagging and tracking of marlin and tuna throughout the Atlantic Ocean. They explore the use of satellite tags and archival tags to collect data on the fish's behavior, including their location, depth, and temperature, and why it is important. They also discuss the challenges of tag recovery and the importance of collaboration with fishermen. The conversation highlights the physiological adaptations of bluefin tuna and their exceptional ability to cross the ocean. The rebound of the bluefin tuna population is also discussed, along with the importance of fisheries management and the economic impact of the fishery. Chloe offers advice for young scientists, emphasizing the importance of following one's passion and staying open to opportunities.

Takeaways

Chloe Mikles is a PhD student studying bluefin tuna and blue marlin movement ecology and population structures.

Tagging fish is an important part of Chloe's research to track their migration patterns and understand population differentiation.

The bluefin tuna fishery in North Carolina is regulated by size limits and quotas, and the fish are harvested for commercial purposes.

International collaboration is crucial for the management of bluefin tuna populations, as they are highly migratory and cross the jurisdictions of many nations.

Proper handling and care of tagged fish, such as minimizing air exposure and swimming the fish before release, help reduce mortality rates. Satellite tags and archival tags are used to track the behavior of marlin and tuna, providing data on their location, depth, and temperature.

Tag recovery missions can be challenging, as the tags are small and can be difficult to locate in the vast ocean.

Bluefin tuna are endothermic fish, able to regulate their body temperature and withstand a wide range of temperatures.

Foraging hotspots and oceanographic conditions play a role in the feeding patterns and migration of bluefin tuna.

Collaboration with fishermen is crucial for successful research and fisheries management, as they have valuable knowledge and observations of the fishery.

The rebound of the bluefin tuna population demonstrates the effectiveness of strict management regulations and the importance of sustainable fishing practices, despite the many challenges that can be derived from these efforts.

Find Chloe on instagram at @coastal_chloe

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TRANSCRIPT

Katie (00:22.905)
Hey, what's up you guys? Welcome to the Katie C Sawyer podcast. I'm sitting here with Chloe Mikles, a remarkable young woman that I have been fan-girling over on the internet for years now. Chloe, thank you so much for being here with me.

Chloe (00:37.698)
Thank you so much for having me. Yeah, I feel like likewise, I've been fangirling over you for years too. So it's always fun to sit down and talk with you.

Katie (00:45.849)
That's so sweet. I really appreciate it. All right, you guys, Chloe is a PhD candidate at Stanford University, working with Dr. Barbara Block, a legend, studying bluefin tuna and blue marlin, movement ecology and population structures. Chloe, can you tell our listeners just like a brief synopsis of what that means?

Chloe (01:07.882)
Yes, so yeah, we oftentimes get caught up with like tossing in a lot of scientific jargon with our work. So Basically, I am in graduate school and for my dissertation work. I am learning from my advisor Barb Block and I am doing everything from going out into the field to tagging the fish which is the most fun part and probably what we'll talk the most about and then reading a bunch of papers to the scientific literature and

I do some lab work as well, and then it all ends up, the culmination of the PhD is basically writing a bunch of scientific papers that summarize our findings.

Katie (01:47.477)
So what kind of questions are you asking about these populations?

Chloe (01:53.258)
So you can start off like very, you can go from very simple to very complex, basically, these questions. The most basic question is, we're putting tags on animals to see where they go. And you can make that more and more and more complex. So for example, from Marlin in North Carolina, blue marlin have been tagged all over the world, but not that many have been tagged off the coast of North Carolina. So by focusing efforts regionally in different locations,

we can get a better idea of where the fish that pass through there go. And basically like if their migration patterns are different, if there are different populations of fish that are traveling elsewhere and just trying to learn more and more about these fish because it's so hard to study the ocean. I mean, it's not like, you know, a deer or a mountain lion or something where you can actually like watch where they go and track them or, you know, put a radio color on them and see where they go. The ocean is really hard to study. Everything's underwater.

Everything's innately then more cryptic. Um, the technology is much more difficult to actually get something that can track animals underwater. So the more tags that we put out and the more data that we collect, it's like, we're constantly learning more about these fish every single time.

Katie (03:07.065)
really love that you just like compared the ocean towards land mammals and land predators out there and animals that we've been studying and trying to manage for a long time. We still have so far to go to properly manage our wildlife on land and the ocean is that much more difficult to do. So we'll get into that a little bit a little later because I want to really touch on what you're doing and what kind of questions and answers we're getting from that. But for the sake of

Chloe (03:18.536)
Mm-hmm.

Chloe (03:22.764)
Right.

Chloe (03:26.322)
Exactly.

Chloe (03:32.415)
Yeah.

Katie (03:36.979)
I'm a blue marlin girl. Let's focus our energy on the bluefin tuna because it's just there's such fascinating animals and I have so many questions for you. So first off let's start with where you started. Where did you grow up?

Chloe (03:38.982)
I know. Cool. Yeah. Mm-hmm.

Chloe (03:55.074)
So I grew up in North Carolina and that is, yeah, that's a big reason why I've chose to study these fish for my PhD. So my family had a place on the coast of the Southern Outer Banks. And I just grew up there always being so fascinated by the ocean. And then kind of like in my most formative years when I was an undergrad and like right out of college, I made, you know, I made some of my best friends in my life and was fishing constantly. And...

that reason, like, I love animals. I have always been passionate about studying them. It probably could have been anything, but the fact that, like, in those years I became so obsessed with offshore fishing, that's, yeah, that really did it. I know. Yeah. So...

Katie (04:38.381)
I got chicken skin. I feel that. I feel that on so many levels. So you did your undergrad at Cornell, right? You had a, didn't you have a full ride scholarship swimming?

Chloe (04:51.17)
So I did swim there for four years. The Ivy League actually doesn't provide like athletic scholarships, which is interesting. Yeah, but yes. So I swam at Cornell for four years. I majored in animal science. My original plan was to be a vet because I loved animals. And then I was doing a couple of internships with North Carolina State University and their Marine Station on the coast, actually working with both like fisheries biologists and Marine veterinarians.

Katie (04:53.111)
No big deal.

Chloe (05:21.038)
And I was like, this is so cool. Like I didn't realize that there was a career where you can actually study the ocean. Like I was getting paid as an intern. I mean, not much, but I was getting paid as an intern to go offshore and tag Mahi. I was like, this is so much fun. This is so cool. Um, and then as far as bluefin tuna, um, I just saw firsthand how important that fishery was to the local community. And it was like this amazing seasonal thing where every winter,

Katie (05:35.441)
Yeah.

Chloe (05:50.994)
It's like everyone would be commercial fishing for them. Like you would get your hardcore commercial fishermen who fish all year round fishing for bluefin tuna. But then you would get people who just do different jobs, um, take off weeks to partake in the commercial bluefin fishery for a couple of weeks. And yeah, it's a really different, I think it's a very unique commercial fishery. It's very different from most places in the country and the world. Um, it's a very short season, but

Katie (06:07.493)
That's fascinating.

Chloe (06:19.934)
I saw how much money it brought in to the local community, how excited people were, like, you know, there'd be little kids coming to see the bluefin brought in. And it was just like this, and it coincides with, you know, Thanksgiving and Christmas. So it's like this holiday season, just an extra excitement to the holiday season.

Katie (06:39.013)
Definitely. Tell us a little bit. So there's three populations of bluefin. There's the Atlantic bluefin, the Pacific, and the southern bluefin, correct?

Chloe (06:48.806)
Yeah, so those are three different species. It gets very complex when you start, yeah. So there are different species of bluefin tuna and then they're within the Atlantic, there are different populations. So it can get very complex depending on, yeah. Mm-hmm.

Katie (06:51.294)
Okay. Okay, right.

Katie (07:00.261)
So, right? And the more we know, the less we know. So in North Carolina, you're fishing for, or the commercial industry is fishing for bluefin, the Atlantic bluefin tuna.

Chloe (07:08.508)
Yeah, that's the best way of saying it.

Mm-hmm.

Katie (07:19.129)
Tell me a little bit about the sizes of fish that are harvested and what the regulations are there. Like how many tags, what the release ratio might be, like give us a little bit of insight into that fishery specifically.

Chloe (07:19.211)
Yeah.

Chloe (07:25.302)
Mm-hmm.

Chloe (07:29.506)
Hmm.

Chloe (07:35.242)
Yeah, so specifically in North Carolina, well, actually just federally in the United States, a bluefin commercially has to be over 73 inches. So that's a pretty big fish. In North Carolina, it's a mixed size class of, I mean, you get fish probably as small as 50 inches and up to like upwards of 110. So it's a big range, but what's nice is you're not getting like a ton of the really little ones.

Like you might get off the coast of Massachusetts, or not really little, but smaller. Yeah, I don't know if that upset anyone, but compared to the giants that you get in Nova Scotia or, I mean, people in Massachusetts still get really big ones too, but you know what I mean.

Katie (08:10.021)
Careful.

Katie (08:16.263)
Right.

Katie (08:21.445)
Yes, of course, of course, yes. We love you Massachusetts. So 73, you said 73 inches is qualifies as a giant, correct?

Chloe (08:26.606)
I don't want to call anyone out.

Yeah, that's.

Um, yeah, I think so. I forget all of that. Noah has it all spelled out, but 73 inches to harvest commercially. Yeah.

Katie (08:36.069)
That's okay. We don't... Yeah, yeah. And how many tags or how many, is it a tonnage or is it like how much can be harvested in the season?

Chloe (08:48.678)
Yeah. So it's based off of quota. And what makes this a really tricky fishery for people also is that once the quota is met or they predict that it's about to be met, they'll close the fishery immediately, like effective, like tomorrow at midnight, essentially. So you really don't have a great idea. Like when you start, I mean, you can, you know, if North Carolina knows like, Oh, we're going to get 60 metric tons for December. Then people have a good idea of.

how quickly that will fill up, whether that's gonna be a week or two weeks, always depends on how good the fishing is, the size of the fish, the size classes that are coming through there. And then there's a limit of one per vessel per day.

Katie (09:29.837)
Okay, that's interesting. Really cool. So that's all fine and dandy. NOAA regulates federally in the U.S. But these are highly migratory species. So how does that work on an international level?

Chloe (09:34.974)
Mm-hmm.

Chloe (09:40.206)
Yeah

Chloe (09:43.506)
It's, yeah, that's the problem of the bluefin tuna and other highly migratory species is that they cross the jurisdictions of many different nations. I can't remember what the number is. I think for like all bluefin tuna, it's like over 50 different nations that are competing for this resource. So if you're a bluefin tuna, everywhere that you go, someone's trying to catch you. So in the Atlantic, they are managed by this international organization called ICAT.

um, which I'm going to blink on the acronym, the International Commission for the Conservation of Atlantic Tunas. And they manage, bluefin, thanks, um, there are so many different, across the world there, like seven different, they're called RFMOs, Regional Fishery Management Organizations, and they all have like, similar, slightly similar, but differing names. It's hard to keep them all straight, but they manage for the most part all the highly migratory species of their set region.

Katie (10:21.709)
You nailed it.

Chloe (10:43.562)
So they set the quotas for different countries and perform the stock assessments and do all of the complicated data analysis and politics.

Katie (10:54.373)
So the politics are done internationally, regulated internationally as well as nationally. But there's so many questions we still have about this tuna, which is why your work and Dr. Block's work and all the work at Hopkins is so important, correct? Now go for it. No, no, no. Tell me what you just say.

Chloe (10:59.11)
Right. Correct, yeah.

Mm-hmm.

Chloe (11:09.61)
Yeah. Mm-hmm. And it's, oh, go ahead. Oh, I was going to, it's really an international effort. Like, yes, we have our lab that's based at Stanford, but we are working with collaborators all across the world, from Canada to Spain, Italy. There's a country where bluefin tuna go, you name it. We've probably worked with them in some regard, as far as getting samples or tagging fish. So it's, oh, right. Yeah.

Katie (11:34.265)
That's awesome. I was able, and you know this, but I was in the Canary Islands with the On Location when Tag a Giant Foundation came over and we helped them catch fish to tag four-year studies and it was in collaboration with the University in Barcelona. So that was really incredible. I hope that you and I get to go do that one day. Have you been over there?

Chloe (11:42.306)
Mm-hmm.

Mm-hmm.

Mm-hmm.

Chloe (11:54.282)
Oh, mm-hmm.

Chloe (11:58.854)
I know. I haven't. It is my dream to go there. I want to go so badly. I'm gonna push for it this year. I have a lot of work to do. So unfortunately, like the further... yeah.

Katie (12:08.953)
You're in your fourth year, right? You're in your fourth year, so it's kind of busy, right?

Chloe (12:14.018)
Right, the further you get in the PhD, it's probably the more data analysis and the less fun in tagging, but hopefully I get a chance to get out.

Katie (12:21.913)
That's why they hook you early. That's cool. Okay, so let's go ahead and talk about the tagging. Let's talk about what these programs look like. I wanna know what Taggagiant's doing over in the Canaries and what they're doing in North Carolina and everywhere else and what we've discovered from them.

Chloe (12:24.035)
Yeah, exactly.

Chloe (12:28.12)
Mm-hmm.

Chloe (12:37.14)
Mm-hmm.

Chloe (12:41.758)
Yeah. So what's cool is basically everywhere that we go, we are working with the local community that's there. Like, we're in California. We can't just show up somewhere and pretend like we know how to catch bluefin tuna and just go off and be successful. Like, that would never work.

Katie (12:58.048)
I love the picture you just painted. That was perfect. Keep going.

Chloe (13:02.43)
So, you know, whether it's Nova Scotia or the Canaries or North Carolina, we're working with commercial and recreational fishermen in those locations who are the experts of catching bluefin in that spot. Like, you know, when you're in the Canaries, like, it's probably very different fishing than if you were in Southern California or if you were somewhere else. So, it's really special because I get to learn when I travel to these locations, all of the, you know, very regional specifics.

what everyone has, you know, their different superstitions and their different techniques and what they swear by and um here do I could you lose me I'm oh okay

Katie (13:37.397)
Oh no. Hold on.

I did lose you, but I think it might have been on my side. Oh shoot, let's start. I heard from regional specifics, so if you could kind of go a little bit back and we'll try again. Sorry.

Chloe (13:54.582)
Okay, no, you're good. Yeah, so when we travel to these different locations, we really just get to spend the time working with the commercial and recreational fishermen who all have these regional specifics of gear types and superstitions and things that they swear by. And it's a really cool opportunity to learn. And that's the reason that we're successful because we have the people that are experts for that region helping us tag the fish. So.

It usually requires a lot of complex permitting to make sure that we get everyone, you know, on the same page, but usually people are really excited and, uh, really helpful and people are just innately curious about these fish. And, um, for the most part, everyone's very happy to be a part of it. So it requires a lot of coordination, but, um, it's great cause we get to tag fish of different populations, fish of different age and size classes and

The goal for most of our work is to track these fish to their spawning grounds. And in the canaries, those fish are mostly going to spawn in the Mediterranean sea. In North Carolina, it's a very mixed batch. We get some that are going to spawn in the Mediterranean sea, some in the Gulf of Mexico. And then there's a spawning location that is, um, people are working really hard right now to understand better called the slope sea, which is

off the coast, basically north of Hatteras all the way to the Scotian Shelf. It's like this weird kind of like shape off the continental shelf and bordered by the Gulf Stream. So we've discovered that there are some fish spawning there. So the goal is to track these spawning fish and figure out where they're going. And to understand like, oh, in Nova Scotia, maybe we have

predominantly Gulf of Mexico fish, but maybe that's shifting year to year. So you wanna know which population the fish originates from to be able to better manage the stock. That's a hold.

Katie (16:00.197)
So, there are two, maybe three, maybe more populations of bluefin tuna in the Atlantic. One population is what you're dubbing the med population, and the other one is the gulf population. So, what you're saying is these fish consistently go back to their same spawning grounds once they're of maturity every year. Wow.

Chloe (16:04.942)
Correct, yeah. Right. Yes.

Chloe (16:21.214)
Mm-hmm. Yes, that's our understanding. And I mean, sure enough, we're going to get one day that goes to both and throws the whole thing out the window. But for right now, the understanding is, yes, that they're managed by ICAT as two populations, the Gulf and the Med for sake of simplicity. And they'll refer to that as the Western and the Eastern populations. So.

Katie (16:30.289)
I'm sorry.

Chloe (16:47.134)
Yeah, it gets, it gets complicated because then they're mixing in the middle of the ocean. But we do, I've been working on a lot of tagging data showing that they repeat, visit these spawning locations year to year, when we can have longer term tags on them.

Katie (17:02.297)
and you take little samples, are these populations genetically different?

Chloe (17:07.551)
So that is the question of my PhD. How did you know? So yeah, my PhD work is really aiming at specifically characterizing these populations from an ecological movement-based standpoint and also a genomic standpoint. So there have been a lot of different genetic markers used over the years to try to characterize and figure out how they're different.

from smaller subsets of genetic markers across the genome. People can say, oh, this one's Gulf, this one's Med, this one is maybe something in between, not really sure. So I'm using the whole genome of the animal to try to really increase the amount of markers that we can use to differentiate them. So yeah, so when we go out and we tag the fish, I will usually get a small thin clip from them and...

we try to get a fin clip and a muscle biopsy. And sometimes, you know, things are chaos on a boat and you miss them, which is too bad. But we try to do our best and get as many as possible. Yeah, exactly. So we get those and then I'll go and collect samples from fish that are landed also whenever I have the time.

Katie (18:10.413)
Because you have like a 600 pound fish on the deck.

Katie (18:22.993)
So, okay, for the listeners that might be like, wait, what is this? You're actually taking parts, parts of a living animal and putting it on the deck and that sounds horrible. You terrible person, Chloe. You're awful. Anyway, let's talk about the process and how, and how it's not at all terrible and what is, what, what type of measures you guys take to make sure that fish is as comfortable as possible.

Chloe (18:26.958)
Yeah. Right.

Chloe (18:36.974)
Yeah, the process.

Chloe (18:47.722)
Yeah. So part of it, you know, it all starts when you hook the fish. So we really try to use, always use circle hooks to maximize being hooked in the corner of the jaw. So that makes one thing easier. And then you also want the fight time to be as quick as possible. So we're not trying to be sporty about it. We're just trying to get these fish into the boat as quick as possible. When we get them into the boat, which is also a difficult process, we have to hook the fish basically in its lower jaw.

and pull it up onto the boat with a rope and it usually takes several people depending on how big it is. And then once the fish is on the boat we have it in this blue mat that you'll see in a lot of our pictures. And someone like hand sewed that mat for us a long time ago and I don't like that's not something you can just go out and buy like someone made it specifically for our work and has handles on it so we can turn the fish. But that protects the...

Katie (19:20.588)
Mm-hmm.

Katie (19:40.737)
Sorry, I'm laughing because I remember when Robbie showed up in Gomera with this hand-sewn mat and I was like, it was massive. And those boys, man, they were packing them up on the flight for the flight back and I was like, what are y'all doing? It was making so much noise. Anyway, continue with your mat. I interrupted you. It's just a fond memory I have. But it, talk about a little bit before you go on about the purpose of that mat.

Chloe (19:59.54)
No, you're good. Yeah.

Katie (20:07.429)
and sliding that fish onto the deck and the slime of the fish.

Chloe (20:08.614)
Yeah, mm-hmm. Right, so that's important, as you just said, yeah, to protect the fish's slime. And, you know, there's a lot of stuff, like the deck of the boat is made to be grippy so that we are not slipping around on it. When, you know, you have a mate in the cockpit trying to wire a fish, like, you need to have your feet be grippy on the ground, so, but that is really damaging the fish's skin. So, hence our mat. And then we stick a hose in their mouth to irrigate their gills.

So we're always checking like whatever boat we're tagging on, like I'm bugging the captain, like, Hey, is your hose a high enough pressure? Because we need a lot of water moving through this fish's gills. And then, um, because yeah, a fun fact about bluefin tuna and other, um, highland migratory fish is that they have to be moving forward to breathe underwater. So they use, as you're familiar with a process called ram ventilation, which is like the literally need water being pushed through their mouth.

to irrigate their gills. So if you stop them, yeah. Yes. I think, yeah, some species of sharks. I'm not a shark expert, but I don't know. But yeah, bluefin and blue marlin for sure and other tuna species. So, and they're the ones, you know, they're moving fast essentially. So if you stop those fish,

Katie (21:08.845)
Same with billfish, sharks, correct? Mm-hmm. So if you stop them.

Okay, yeah. Let's not go there. Go on. So if you stop at tuna...

Chloe (21:33.95)
it would be very hard for them to be breathing. So that's why we put the hose in their mouth. And then we put a cover over their eye just to protect their eye. I mean, they could be looking around and seeing what we're doing. They're honestly like too big to move around while we're doing anything for them. Like when you put this big fish on the deck, it's usually not big enough to actually like lift its tail up in like, you know, gravity is a much stronger force than they're facing in the ocean when they're moving. So they usually can't lift.

their tail up that high to start doing like the tuna slap on the deck that you see like smaller ones do. Right. And then, yeah.

Katie (22:09.073)
the smaller ones yeah. I thought the I thought the towel over the eye was to keep them calm to keep it dark and kind of just

Chloe (22:20.142)
Maybe. Yeah, I mean, protect their eye, keep it. I mean, I don't really know if we didn't put the towel on their eye if they would be less calm. We could test it, but it's just something we always do. So maybe. Yeah.

Katie (22:31.46)
No. Yeah, of course. It's like a spa day for the comfort of the fish, my bad.

Chloe (22:38.386)
They're being abducted by these human scientists and probed and then sent back into the ocean. I would love to know what they think. And then while the fish is on the deck, we get a couple measurements. So we get their curved fork length, their girth, and then I take a fin clip, a muscle biopsy, we stick the tags in. We also put a spaghetti tag in the fish that has a phone number to call.

Katie (22:40.578)
Ha!

Chloe (23:05.418)
So those, I mean, a lot of people in tournaments are just for fun, we'll go out and spaghetti tag fish. And that'll be really valuable information for a point A to point B. So we have that as an identifier on there. Usually one sort of electronic tag. Sometimes fish get two tags. Um, and then we turn them around and set them back. And because we're tagging them with electronic tags, we actually know what happens to the fish. So if the fish were to die, which

for the most part does not happen. I mean, it's very rare. I'm not gonna say it never does. Every once in a while, unfortunately, one dies, but we know and we report that right away. So that's part of the research. Like if a fish weren't to make it, which rarely happens, the tag actually pops off of the animal. So there's a sensor on there that basically, if it sinks to the bottom and it doesn't move for three days, then the tag pops off.

Katie (23:40.741)
science.

Chloe (24:04.47)
But the great thing is that doesn't usually happen. So we know that the fish, yeah. Right.

Katie (24:07.033)
That's crazy. So you don't have to wait the 360 days of the tag life. It's just, it lets you know immediately.

Chloe (24:16.498)
Yeah, we're usually just like, I mean, just for the, you know, we always like hold our breath for a couple of days. And we're like, if we haven't heard from it, then it's good. The fish is moving. It's somewhere. Like, you know, I was, I tagged my first blue marlin last year and I was just like hoping, hoping I was like, this is my first one. Like, I hope it's going to be okay. And, um, you know, also that I placed the tag correctly and it doesn't pop off of the animal and then if you don't hear from it, exactly. Yeah. These.

Katie (24:41.349)
That's an expensive mistake.

Chloe (24:45.398)
The satellite tags are like four or $5,000 a piece. So it's nerve wracking. Yeah, you wanna make sure that it goes well. Right, and then for that part, we're also taking as good of care of the fish as possible. Like if a fish comes up on the boat and it's like a seam or comes up to the boat, usually we don't bring it on the boat if it looks stressed. You know, like if the color is off, if it doesn't look good, if we ever accidentally get a tail wrapped fish, God forbid that, like we cut it loose, let it go, try to swim it to get it moving again.

Katie (24:51.157)
It's super, it's a lot of pressure.

Chloe (25:15.398)
and we're not going to put a fish that isn't in great condition through the stress of tagging.

Katie (25:20.729)
Yes, so for the listener, Chloe just mentioned if we ever get a tail wrap fish. We were talking earlier about how tuna and a lot of pelagic species need to be moving forward to breathe. So if you get your fishing line wrapped around the tail of the fish, you're going to end up pulling it from the back, backwards and then pushing water through the gills in the wrong direction. So that's how they asphyxiate. But there are ways as an angler and a captain to help mitigate these issues and make sure that they don't happen.

Chloe (25:23.31)
Mm-hmm.

Chloe (25:29.803)
Mm.

Chloe (25:38.572)
Right.

Chloe (25:42.754)
Mm-hmm.

Katie (25:50.663)
if they do happen to address it early and make sure that fish lives through the process. Now we'll get into that another time but I just wanted to touch base on why tail wrapping is such a bad thing. Now Chloe what I find fascinating is that these bluefin tuna and other tuna are so stout they're so sturdy and they can take that type of

Chloe (25:59.49)
Mm-hmm.

Chloe (26:04.15)
Yeah, thank you.

Mm-hmm.

Chloe (26:16.322)
Mm-hmm. Right.

Katie (26:20.661)
I don't want to say harassment, but that type of, um, what's the word I'm looking for? Yes, yes, and, and then live on it happily. I mean, like you, like you said, the science shows, the data shows. Now, I said we weren't going to talk about blue marlin, but Bill Fish, you don't take them out of the water to tag them, do you?

Chloe (26:24.241)
Stressed, yeah.

Chloe (26:31.155)
Yeah.

Chloe (26:38.505)
Yeah.

No. So billfish are considerably more fragile than bluefin tuna. And like the smaller billfish, like spearfish and sailfish are very, very fragile for whatever reason. Those fish, like, you know, in the States and I can't remember if other countries, but in the States, it's illegal to pick one up out of the water unless you're going to harvest it. So those fish, you want to

Chloe (27:11.074)
For pictures sake, you know, the GoPro stick was invented and people have found a way to like get a great picture shot of a sailfish next to the boat without having to bring it out of the water. Yeah. Exactly. They die, right?

Katie (27:21.209)
So much prettier than when they take them out of the water. They get all dark, they're ugly, and then most of the time they die. But in the water, they're properly aerated, they've got all their beautiful colors. So definitely encourage the listener, if you guys go bill fishing, to keep your fish in the water and take a picture that way. But Chloe, how do we know that they don't survive and why has it become legally mandated to keep these fish in the water?

Chloe (27:31.566)
Right.

Chloe (27:44.158)
Mm-hmm. So there have actually been a ton of scientific studies evaluating catch and release mortality. So that's basically the percentage of fish that are caught angled a certain way and released. So there's a huge body of literature and a lot of scientists that work on that question and so many different species. And you can get very, very specific with it. You can have a certain, like there are different, basically more catch and release mortality estimates for.

every single different species and every different way of capture. So you'll have someone evaluating light tackle catch and release mortality on, um, blue marlin or bluefin tuna or the same, you know, the same for any other species. And you're really trying to estimate like, okay, what can we do to minimize, um, mortality for these fish? And a lot of times it's, um, quicker fight times, limiting air exposure, limiting handling, um,

It's things that all like kind of make sense when you spend a lot of time out on the water and you see how these fish react. But you know, it's like when I first started trout fishing, I was like, wow, trout are super fragile. Like you know, you fight those fish too long and they like can't even swim again. So ocean fish in general are more are a lot tougher. But yeah, we don't bring I think that some of the earlier studies with blue marlin, maybe they think.

Katie (28:55.513)
Yeah.

Chloe (29:10.73)
At some point people probably were bringing them on the boat and then they were seeing from the tags that they just don't survive. Or if you don't swim the fish when you're releasing it. We found from a lot of tagging work that if a fish is really tired after tagging it, you really need to take the time to swim it and release it. That practice thankfully is caught on widely in the whole bill fishing community and I see people having those videos. Because everyone wants that video of showing that your fish swam away.

Katie (29:33.474)
Yes.

Katie (29:39.633)
The healthy release. Yes, we're not out there because, exactly, we're not out there because we don't like them. So no, they're incredible. We always swim, especially our big fish, we always swim our big fish. And you can tell, like I mentioned earlier, the coloring of the fish helps show how healthy and the lack of color shows the level of stress. So how do you tag your marlin?

Chloe (29:39.766)
We all care so much about these fish. Yeah, we don't want them to die. Ha ha. Right. Mm-hmm.

Chloe (29:57.249)
Right.

Chloe (30:02.123)
Mm-hmm.

Chloe (30:06.006)
So yes, the marlin, it's a huge coordinated effort between captain, mate, or mate's plural sometimes, and whoever's tagging the fish. So usually, it depends on whether you're tournament fishing or what, but usually the captain will try to back down on the fish quickly to minimize the fight time. And then as long as the fish isn't too green, like you want it to be somewhat under control also. So it's a really fine balance. Like.

Katie (30:33.029)
Green is not a color, it's a behavior.

Chloe (30:35.47)
Green is a behavior, yes. Thank you. So you'll have a fish, you know, you can't safely tag a fish that is still jumping and tail dancing across the water. You need it to be somewhat under control, but not too tired that it's like having a hard time moving. So it's this really fine balance. And then, you know, it requires the mate to get it close to the boat. And then we like to place the tag right under the dorsal fin.

And I think I sent you some pictures that we can show listeners later, but that is like the spot where you want to tag the fish to help like it's above their lateral line, which is a really cool sensory organ that we can talk about later. Um, but you want it to be like deep into the muscle. Um, but then like it's, you really have to avoid like damaging any specific organs. So it's like kind of in the shoulder of the fish, I guess. Um, and then it's in the spot that.

Katie (31:06.149)
Definitely.

Chloe (31:32.562)
really minimizes any sort of drag also. So we don't want this tag, you know, and we also don't tag small marlin. We only tag ones that are big enough so that the tag actually isn't interfering with their, or minimally interfering with their day-to-day activities, swimming life. So it can be hard because like you'll get a fish next to the boat, a marlin, and the mate's holding on as hard as he can trying to get it in the right position and the fish is just like rolling over like belly up.

Katie (31:50.26)
I love it.

Chloe (32:02.326)
You're like, well, I need you to be sideways so you can get the tag in on the side. Right. So it can be very tricky to keep the fish in the right position. Yeah. And then we have a long tagging pole that AFCO makes that we, uh, is super easy and lightweight and you can just stab the tag into its back and let it go on its way. Yeah.

Katie (32:02.335)
Yeah.

Katie (32:05.785)
Give me your dorsal!

Katie (32:12.601)
That's... yeah.

Katie (32:25.765)
Let it go on its way. Awesome. Switching gears back to Bluefin. Let's talk, and it's the same thing with these blue marlin tags too, but I really wanna focus on these tuna of yours. What all do the satellite tags, what type of information do they gather, and how does that information get brought into the day by day of the fish? Like telling us about the day by day of the fish.

Chloe (32:31.062)
Yeah.

Chloe (32:34.998)
Mm-hmm.

Chloe (32:49.694)
Yeah. So the satellite tags, I wish I had one to show you, but it's basically this. Yeah. So the satellite tag is this waterproof pressure proof package that contains a computer chip inside a battery, all of these different sensors. So start from like the top of the tag. It has a light stock that is measuring the light levels.

Katie (32:56.249)
We'll show it on while you're talk.

Chloe (33:16.734)
And from that, we can actually mathematically geolocate where the fish is. So we know when the sun rises and we know when the sun sets and we use different mathematical algorithms based off of that to position the fish. So that data all gets stored inside the tag. Then we also have an external temperature sensor that's sensing the environment around the fish, the water that it's in. So when it's diving deep or on the surface or travel anywhere, you can get the temperature of where the fish is.

And then there's a pressure sensor, which you can calculate depth from. So as you go down, pressure increases and we can determine basically to the exact meter. Science uses all metric, which makes things complicated going back and forth, but we can figure out exactly the depth of fish is swimming at. And then, so that's a satellite tag. There are also, I can talk more about later, archival tags that we surgically implant in their bellies. And the only difference between those is,

The archival tags also have an internal temperature sensor, but then they also stay with the fish for life. So the satellite tag is this package that detaches from the fish after a pre-programmed time. So in its computer sensor, and depending on what sort of experiments we're doing, we'll set that time differently. So you can set it to pop off after a couple of days, after a week, after two weeks, you can set the exact number of days, but usually we set them to a year, or as long as we can.

So the battery life on those lasts about a year. We'll pop the tag off and then it actually starts transmitting its data up to the satellite. And it just starts like dumping the data up to the satellite as fast as it can before it dies. What's great is that if we get the tag back, we get the entire record. So when the tag is uploading all the data to the satellite, it's not able to get like everything at the sampling rate that it's taking. So.

It might be recording a data point every 10 seconds, but that's too much data to send up to the satellite. So it'll send like a shorter summary. Like maybe you have something like every minute or every couple of minutes, a position, a depth, a temperature. Um, so it just depends on the resolution of the data. I can keep going. Yeah. There's a lot to it. It's.

Katie (35:33.669)
That's amazing. So yeah, no, wait, I'm like, I'm kind of blown away about the fact that it records a data set every 10 seconds for a year. Like...

Chloe (35:42.658)
Mm-hmm.

Katie (35:43.885)
That's a lot of data, but then this concept of, you know, wherever the bluefin tuna is 360, 65 days later is where the tag's gonna pop up. So then you have this little tag that's gotta be like what, six inches long, maybe eight, that's floating around in the ocean and it's like, good luck scientists, come and find me before I die.

Chloe (35:46.27)
Yeah. Mm-hmm. Right. Mm-hmm.

Yeah.

Chloe (36:00.991)
Yeah.

Mm-hmm. Yeah. Exactly. And usually, right, usually they don't pop off anywhere convenient. Like, they're not going to pop off like right in your backyard. I mean, one did once, which is great. But, um...

Katie (36:13.515)
I'm sorry.

Katie (36:18.563)
That's awesome.

Chloe (36:21.986)
Blue Marlin that I tagged last year just popped up right off the coast of Belize, which was super exciting. So Robbie, who you know, flew down to Belize to try to go get it, and he went on this tag recovery mission. And as soon as he got out on the water, the tag died, and he could not find it. And it's just this tiny tag floating in the middle of the ocean. And I mean, with ocean currents and weather patterns, yeah. So he never found that one, unfortunately.

Katie (36:28.645)
That's awesome. Mm-hmm.

Katie (36:46.969)
You do what you can.

Chloe (36:51.882)
Maybe it'll wash up on a beach. That'd be great.

Katie (36:51.911)
Have you gone on...yeah right. Have you gone on tag recovery missions?

Chloe (36:58.562)
Yes, they are difficult. So you're looking for this little black tag that's barely floating in the ocean. So it's hard because you have so much. It's a mini computer that you've then, you know, made waterproof, made pressure-proof, and made like able to fit on a fish. And then you also need it to float. So it barely floats. Like it's just barely sticking out of the ocean, sometimes bobbing up and down.

and it has this little antenna that's kind of swaying back and forth, but it's black. And anyone who's been out in the ocean, like if you drop something black, it floats. Like it's not bright, but that's because we don't want other fish to be picking at it. So if it was a bright color, it's just kind of this fish swimming around and it might get bitten off by another animal. So that's why we make them dark. But we use this device, it's called a goniometer. And yeah, I know.

Katie (37:39.002)
Right.

Chloe (37:55.138)
Don't ask me how it works. It's like an omnidirectional stick that you put the code in of the tag and it tells you like it's like a game of hot and cold. Like you're getting warmer, you're getting further away. And once like I, the first tag recovery mission that I did by myself, I went with my friend

Katie (37:55.341)
I'm in. I'm into it.

Chloe (38:23.178)
And he was like, oh, we use that in the Marines to like locate stuff. It's like, great. Like, so maybe you can help me. Um, so we go off, yeah, looking for this tag, playing this game of hot and cold. You know, sun's going down, weather. Like we had like a very quick weather window and we literally, I have a picture of the tag in the ocean with the sun, like halfway set in the background. And it's like, we barely, barely got it. Yeah.

Katie (38:30.521)
Super.

Katie (38:49.822)
Oh my gosh. You got it. That's awesome. Is that the only one you've been on?

Chloe (38:57.016)
So I have helped get some in Nova Scotia also. Those are actually a lot easier because the fish usually returns to the Gulf of St. Lawrence every year. So we know that it's gonna pop off there. And then it's a big bay. You know, like there isn't the Gulf Stream to whisk a tag off. Like if you don't get a tag in North Carolina within a couple of days of it popping off, it's in the Gulf Stream and it's like on its way to Spain.

Katie (39:15.741)
Right?

Katie (39:22.307)
It's gone.

Chloe (39:23.658)
Yeah. And it's dying, yeah. Yeah. You still get a great amount. So you can tell basically the entire track of where the fish went. And then you get a pretty good summary of, you can get like a good average of the depths and temperatures that the fish likes to be in. So for marlin, we know that they really like to be, they're more surface oriented, they like to be warmer.

Katie (39:26.199)
And it's dying. But you still get, you still get, okay, so how much, if you don't recover the tag, how much data do you get back? Okay.

Chloe (39:54.178)
The bluefin tuna can go a lot colder. The bluefin can go, it's, it has like, it can withstand probably the coldest temperatures of just about any highly migratory species. They're amazing fish. And then we have them going down to the lowest temperature is zero Celsius, which is like freezing basically. So yeah, they're cold. They're warm fish, which is, so they are...

one of the only endothermic fishes. And of, you know, yes. So, I mean, we call it regionally endothermic, but they are warming their core up. So it's this really cool process where, you've probably seen when you like cut open a filet of fish that there's red muscle and white muscle. And in like, I'm trying to think of another good example, in just like a normal fish.

Katie (40:26.661)
fully endo.

Chloe (40:51.83)
The red muscle is on the outside, but in the bluefin tuna, they've basically like evolutionary evolved to internalize their red muscle. So that, so when they're swimming, they're heating themselves up. And then because it's internal, they're able to like insulate their body, retain that heat. And then through a series of their like countercurrent heat exchangers, which is like this very fine capillary network within their body. They're able to retain the heat.

inside. So it's this very, yeah.

Katie (41:22.661)
So is that why tuna meets red?

Chloe (41:26.87)
Um, the meat is really red because it's really concentrated with, um, myoglobin or, yeah. No, I was like, wait, is that correct? So, um, they, they have a lot of, you know, because they're, it's a highly efficient fish, they have a ton of mitochondria and their muscles just like packed full of those and all the oxygen transport. Yeah. It's physiologically they're like.

Katie (41:33.425)
Okay. Yeah. Sorry. Didn't mean to interrupt you. You were on a roll and I was just, I was kind of blown away. Sounded really good to me.

Chloe (41:56.29)
They're a very, very fascinating animal. And that's why my advisor, Barb Block, has really fallen in love with them. Like her, by training, she's a physiologist. So these animals are like one of like the world's physiological wonders, basically, that they've been able to evolve this system that's more mammalian-like. Like we are endothermic. We, you know, can adjust to different temperatures, but fish and reptiles are not. They just kind of, for the most part, they just go along with whatever temperature it is. And...

That's why you get iguanas falling out of trees in Florida when it gets too cold, because they just can't withstand that.

Katie (42:34.541)
Um, what about like yellowfin and blackfin and big eyes? Are they all endothermic as well?

Chloe (42:35.146)
Mm-hmm.

Chloe (42:41.366)
They are, but the bluefin has basically the greatest capacity for endothermy. So they also have similar systems. They're just not basically as strong and developed and evolved as the bluefin.

Katie (42:53.557)
And you were saying earlier, back when you were talking about the populations, you got your Eastern and your Western population and how they're all congregating, seemingly, off the coast of the Midwest of the U.S. And, sorry, Mideast. Mideast of the U.S. Northwest, thank you. Eastern land.

Chloe (42:56.722)
Mm hmm. Yeah. Mm hmm. Yeah. Mm hmm.

Chloe (43:08.658)
Mid- yeah. Northwest Atlantic Ocean. Eastern- yeah, it's- I always get it mixed up. Depends on whether you're talking about the continent or the ocean. Yeah. Northwest Atlantic Ocean is what we usually say. Yeah.

Katie (43:20.247)
Right. Thank you. So.

Thank you. Okay, so how they're all congregating in the Northwest Atlantic Ocean. And what just kind of blows my mind here, and that I really want to emphasize is the fact that these fish are crossing the ocean. And that's not a that's not common. Like even for blue marlin, like it's not common for them, as far as we know, to be crossing the ocean basin. So what does that mean? And how do they?

Chloe (43:39.171)
Yeah. Right. No. Mm-hmm.

Chloe (43:48.351)
Right.

Katie (43:51.117)
Like, do they feed in the middle of the Atlantic? Are there feeding points there? Like, what do we know based on your tagging research that these fish are doing to cross the ocean, and why is that so exceptional?

Chloe (43:53.495)
Mm-hmm.

Chloe (43:58.699)
Yeah.

Chloe (44:03.522)
So yeah, first of all, it's just a very far distance. So yeah, being able to make that migration and of itself is just incredible. We definitely know that there are foraging hotspots just about everywhere. We recently, I don't want to say discovered this spot. I mean, it's this oceanographic condition that we spot that we always, people always knew was there, but we didn't really understand why the fish were there. There's a spot like kind of in the middle.

of the Atlantic Ocean. And there's this eddy called the man eddy that one of my colleagues just published a paper on explaining how the fish are basically drawn to this eddy and that they're feeding on congregations of baitfish. We don't know what the fish are that are there. I'm sure someone knows, but there's like this big feeding aggregation for bluefin tuna that they all love to go to. And it's just this spectacular thing.

before I just kind of looked at the track and they're like, oh, it's just passing through, this must just be somewhere. But we actually see fish year after year returning to that location. So they know that there's some really high quality forage there and then, you know, so there are spots where they can feed as they cross the ocean. But sometimes you'll see tracks where it's just going very quickly and not spending a lot of time diving or, you know, just spending a couple of days passing through a very long distance.

So we can get a really good idea whether or not a fish is actually utilizing, like performing feeding behavior and diving or just swimming.

Katie (45:40.165)
So what are the, like, that's really interesting to me because when you're looking at this data that you're getting from your satellite tag at the end of the year, how do you know what identifiers are there that's showing you that fish fed in that location and what identifiers are showing you that it was just passing through?

Chloe (45:49.292)
Mm-hmm.

Chloe (45:56.45)
Mm-hmm.

So one really cool thing, well, okay, yeah, with the satellite tag, it's usually diving behavior. So we really think that the fish is only diving if it's going to feed or if it's trying to avoid predator, or sometimes they're diving to avoid surface currents. But that we really would have a very hard time understanding. But for the most part, they're only diving to feed or to avoid a predator. So yeah, that would be the way. A cool thing about the archival tags.

is with the internal temperature, you can actually get, you can actually know exactly when they're feeding because when we eat, our body actually warms up. It's called this heat increment of feeding. So when you're ingesting, taking in these calories, that's energy and your body as it's processing that is heating up. So we can actually, there have been some papers showing this with mostly smaller bluefin tuna. You can tell when they like take a bite.

their internal body actually cools down at first because they're getting cold water from the outside or maybe a cold sardine or something. And then it starts heating up as the fish is digesting that meal. And there's this curve of digestion and then it goes back down to baseline. So yeah, you can get this whole study of metabolism in the way that a lot of like human physiologists can also do in a wild bluefin tuna, which is just spectacular.

Katie (47:25.157)
Spectacular. That is fascinating. And with these with these archival tags, not only do you have to catch the fish again to get it back, but you have to like harvest the fish to get it back. What how many do you all set? How many archival tags do you all set out launching a year? And how many have you gotten back in your career?

Chloe (47:26.782)
Yeah. Right.

Chloe (47:45.602)
Yeah, so, oh man, it's, well, I think it's actually worth standing beyond my career. So since I've been putting out archival tags, I haven't gotten a single one back. Um, it takes a long time. So, yeah, not yet. Um, so I'm actually working on tagging data from an archival tag that was placed in a fish in North Carolina in 2012. And it is like the most remarkable. Um.

Katie (47:58.411)
Yet.

Chloe (48:15.358)
study of animal migration. And we've tracked the fish for six years and the battery life on the tag lasted for six years and it was caught in, um, like a pen in the Mediterranean sea and then harvested. So we were actually able to get the tag back. But, um.

Katie (48:20.529)
That's amazing.

Katie (48:29.413)
That's the Almadrabah, right? The Almadrabah fishery in the Med? Do you know about that?

Chloe (48:34.274)
Yeah, I'm not... a little bit. There's... yeah, I've never seen all of it.

Katie (48:37.153)
It's just like a big cultural thing in Italy and Spain. It's old, it's ancient practice of harvesting these fish in pens, but it's pretty spectacular. Yes, but sorry, continue. So that fish was harvested in the Med.

Chloe (48:44.055)
Mm-hmm.

And then Matanza, yeah.

Chloe (48:51.594)
Yeah. Yes. And so over time, it's really a product of like how many fish, how many we get back or how many tags we put out and then how many fish are caught. So if quotas are really low, we actually won't get that many tags back. If quotas are really high and we put out a lot of tags, then over time, so like starting in the late nineties, and if you give it a lag of about

20 years, we'll get close to about like between like 30 to 50 percent of those tags back, which is a huge return rate. Yeah. Like in fisheries literature, like I think a tag return rate of over three percent is considered to be like great. Yeah. So a lot of these fish are getting, yeah, and a lot of them end up getting caught in the Mediterranean Sea, and but this also requires

Katie (49:30.501)
That's... Yeah, that's a lot.

Katie (49:41.881)
success. Yeah, that, I mean, that's wild.

Chloe (49:51.734)
partnerships with the harvesters there so that they know like if there's this weird thing in the belly of the fish like they need to be aware that is something that they need to look out for and that they need to return to us. So it requires again this international collaboration and cooperation and people being supportive of the research also because you know people are like all these darn scientists you know I'm just going to crush this tag and throw it overboard then all the effort is done for nothing you know.

Katie (50:14.698)
Ha ha.

Chloe (50:20.442)
have to maintain those good relationships.

Katie (50:22.965)
And you touched on that earlier about how most people are really excited to have you guys on board and are just genuinely curious about the science and the studies. Have you worked with a lot of commercial fishermen and a lot of recreational fishermen? I want to hear a little bit about your stories with that.

Chloe (50:29.441)
Yeah.

Chloe (50:32.66)
Mm-hmm.

Chloe (50:40.254)
Yeah, so I mean, my best friend from back home, Natalia, who we both know, she, yeah, she is this badass commercial fisherman, fisherwoman. Um, and I learned so much from her about bluefin tuna and just fishing in general. So having that relationship. Yeah. I mean, I, that was, I learned more about bluefin than I feel like most scientists get to, because I was on the water fishing for them.

Katie (50:45.361)
She's incredible.

Katie (50:56.185)
God, that's so cool.

Chloe (51:07.57)
learning firsthand from the people that know the most about them. Because if you're out in the water catching these fish every day, like, maybe you're not a trained scientist, but your observations are all scientific. Like, you know, the great currents, the right tides, the right temperatures, you know, the seasonal migrations of them, when they go, where are they going to be and when. So, you know, exactly right. What they're eating, how to present the bait properly. Like fishing is so scientific in nature. So.

Katie (51:27.341)
what they're eating, what to look for, and all the conditions.

Chloe (51:36.938)
I mean, that's why I feel like I was so drawn to it. Cause I was like, wow, this is like, this is scientific. This is really cool. So for the most part, like fishermen know best where the fish are, what's going on in the fishery. Like if they're the ones that you need to go to, I mean, they know best. So I've been really lucky to have these good relationships and you know, the fishing world is so small. So.

you know, you make one good connection and then, you know, you can go just about anywhere in the world and there's someone who knows someone who knows someone who can connect to you and that goes a long way. Um, and it's right. Exactly. So, you know, every once in a while, of course you're going to meet someone who's grumpy and not excited about the tagging and the science. And that's probably cause they've been around for a really long time and they've seen how the fishery changes and

Katie (52:16.257)
and is so happy too.

Chloe (52:34.198)
You see a lot of things where it's like, oh, it's not like it used to be. Like the fishing was so good back then. But in the case of bluefin, I feel like a lot of people are seeing now how, you know, there were, there's been like the most strictly managed fish in the world. But your people are seeing in their lifetimes, the fish, the fishery rebounding and they're seeing, oh, wow, we're actually seeing more fish in our waters than we were like 10 years ago. Or maybe this year is bad, but.

last year was really, really good. Or maybe that we see a lot of small fish that we know are going to be around and be bigger in the next couple of years. So it's cool. I feel like people have really been able to see like, you know, that fisheries being closed down and management being really strict isn't like, I mean, it's not, it's very contentious. It always is between commercial and recreational fisheries and being a fisheries manager would be a really, really hard

Chloe (53:32.682)
the effects of it and when it does go correctly, when the science, when it's incorporating all of the science, when it's incorporating, you know, the data that the fishermen are collecting, that's all like the catch, you know, that people are reporting that commercial fishermen are required to log their effort. Those things all go into the stock assessment models, make it more precise and that data helps to, you know, provide better management. And that's.

what our science is trying to do. We're trying to provide the best possible data to managers so that they can adequately manage the fishery. Because I mean, we want there to be more of them. We want, you know, fisheries management is by nature economic also. So it's, you know, NOAA fisheries is housed in the department of commerce. So this is an economic resource, not just a really fascinating ecological and animal resource, like it's a wild population that's economically important.

Katie (54:29.837)
It's significantly both for the commercial sector, but also for all the communities that depend on them and for the tourism sector of those communities. So I really like that you just touched on a ton of different stakeholders in this conversation about the...

Chloe (54:29.842)
So if we wait, yeah. Yes.

Chloe (54:37.433)
Exactly. Yeah. Mm-hmm.

Chloe (54:44.854)
Yeah.

Katie (54:49.305)
fishery and the commercial fishermen and the recreational fishermen and the science scientists and how this population has rebounded. And let's hear a little bit about the rebound of this population. Before I get into my closing statements, I just I want to ask you a million things, Chloe. So I think we're going to have to do another podcast episode. I know I don't know where the time goes. I know we're going to have to do it again. But but I want to hear just a brief bit about the rebound.

Chloe (55:04.352)
Mm-hmm.

Chloe (55:08.43)
Oh my gosh, it's already 1058! What? Oh my gosh. Well, yeah.

Katie (55:19.882)
and then we'll get into some closing statements.

Chloe (55:23.278)
Wow, that went so fast. So, oh gosh, I'm gonna get all the dates and decades wrong, but basically the bluefin fishery started crashing in the 70s and 90s, and then there was like, it was, there was a petition to list it as endangered on the CITES endangered species list, that didn't happen. But the population was...

You know, we saw just like year after year from the stock assessments or not. We, I wasn't around the stock assessments were showing the population was decreasing each year and the amount of fish that were making it back to breed and spawn were decreasing those fish weren't producing anymore. So, um, they're really strict, um, management regulations for a long time. And I don't know specifically what those were, but the bluefin tuna, they don't reproduce until they're about 10 years old. So.

Katie (56:18.829)
so old. That's so old for fish.

Chloe (56:20.234)
The hard thing is, like, you have people who are very frustrated, who are like, I've been patient, like, I've been, you know, listening to these rules for so long and I'm not seeing any difference. I'm not like, of course you're not because the fish doesn't reproduce for until it's 10 and then that fish doesn't really recruit up into the fishery until it's about five or six years old. So.

It takes a really long time to see the effects of management and also for management to know if what they're doing is actually effective. So it's a really tough balancing act. Yeah.

Katie (56:53.965)
It's a tough balancing act for everyone. I feel like for the communities that are depending on the fish, but also for the scientists to be standing by their decisions and the rule makers for to be standing by their decisions because like you said, ten years, that's so... In the world of fish, that is so old. And how old do these fish get? Generally.

Chloe (57:00.26)
Right.

Yeah.

Mm-hmm.

Chloe (57:10.507)
I know.

We estimate that they can get as old as 40. So I know. But probably most of them are caught or eaten by something else before they get to that age. So it's a fish eat fish world.

Katie (57:16.933)
WAAA

Katie (57:26.029)
Right. Fishy fish world. All right, Chloe, that was an incredible conversation. I could go on forever with you. It's amazing. I didn't even get into the Gulf of Mexico. So we'll have to do another one on that one. But I do have a couple questions for you closing up. For any listeners out there, like younger listeners that are interested in what you just spoke about, or, you know, understanding, even if it's from fish to...

Chloe (57:34.038)
Yeah, same. Yeah.

Chloe (57:43.394)
Sounds good.

Katie (57:53.797)
birds. I know that you're a big bird girl too. Studied ornithology, right?

Chloe (57:55.731)
Yeah.

Chloe (57:59.858)
Yeah, I did some work with the Cornell Lab of Ornithology as an undergrad and studied lots of different birds there. So it was cool. It was a lot of fun. Yeah. Thank you.

Katie (58:05.229)
that you're seriously one of the coolest people I've ever met. So, do you have any words of advice for young listeners that are that are fascinated by this conversation and want to get into a field of science or you know what are some words of advice?

Chloe (58:19.767)
Mm-hmm.

Chloe (58:25.93)
Yeah, I think that the most important thing is to really like follow your passions and stay true to yourself. Like don't pretend to be someone else just to try to, you know, fit into a certain mold. Like really play to your strengths. Like I mean, everyone has strengths and weaknesses and we can always try to like, you know, bolster up our weaknesses, but just play to your strengths and just don't close the door to any opportunities. You know, like if you get

a really incredible opportunity to partake in something. So like, even if you don't know if you're going to love it, just try it. Because the worst thing that happens is like, Oh, maybe you don't have a great time or you realize like, Oh, maybe like working on fishing boats and collecting this data, like maybe that's not for me. Um, so yeah, exactly. Um, and it's really just about like building your network, like professionally and personally. I mean, it's just, you want to be doing what

Katie (59:09.785)
But I did meet this one cool person.

Chloe (59:24.082)
you love doing. That's the most important thing, like getting through the like, especially doing a PhD. It's a long time. And it's difficult work. So you have to really, really love it. Yeah, I think that sums it up.

Katie (59:37.197)
I love that. That reminds me of, I think it's Mark Twain quote where he says, there's the two most important days in your life are when the day you're born and then the day you find out why. And I just love that. Yeah, it just follow your passion and pursue what really sets your life on fire.

Chloe (59:45.995)
Mm-hmm.

I'm sorry.

Chloe (59:52.414)
Oh, I love that. Yeah. Mm-hmm. Yeah.

Katie (59:58.301)
I think that's really cool. You are an incredible role model for so many people out there, young and old, male and female. I just think what you're doing is absolutely amazing. I really appreciate your time today and I can't wait. We're gonna have to get back on a podcast and talk some more because this could go on forever. You're incredible.

Chloe (01:00:04.654)
Thank you.

Chloe (01:00:15.658)
I know. I can't believe an hour flew by that fast. It's so easy to talk to you. It's so much fun to talk about bluefin and blue marlin. And thank you so much for letting me share some of the science. And yeah, this is a lot of fun.

Katie (01:00:30.693)
Thanks, Chloe!

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In this podcast episode, Katie interviews Chloe Mikles, a PhD student studying bluefin tuna. They discuss Chloe's research on bluefin tuna and blue marlin movement ecology and population structures. Chloe explains the process of tagging fish and the importance of tracking their migration patterns. Katie and Chloe also talk about the bluefin tuna fishery in North Carolina and the international management of bluefin tuna populations around the world. Chloe shares her background and interest in studying bluefin tuna and discusses her PhD work on population differentiation. They also touch on the handling and care of tagged fish and the differences between handling bluefin tuna and billfish. In this conversation, Katie and Chloe discuss the tagging and tracking of marlin and tuna throughout the Atlantic Ocean. They explore the use of satellite tags and archival tags to collect data on the fish's behavior, including their location, depth, and temperature, and why it is important. They also discuss the challenges of tag recovery and the importance of collaboration with fishermen. The conversation highlights the physiological adaptations of bluefin tuna and their exceptional ability to cross the ocean. The rebound of the bluefin tuna population is also discussed, along with the importance of fisheries management and the economic impact of the fishery. Chloe offers advice for young scientists, emphasizing the importance of following one's passion and staying open to opportunities.

Takeaways

Chloe Mikles is a PhD student studying bluefin tuna and blue marlin movement ecology and population structures.

Tagging fish is an important part of Chloe's research to track their migration patterns and understand population differentiation.

The bluefin tuna fishery in North Carolina is regulated by size limits and quotas, and the fish are harvested for commercial purposes.

International collaboration is crucial for the management of bluefin tuna populations, as they are highly migratory and cross the jurisdictions of many nations.

Proper handling and care of tagged fish, such as minimizing air exposure and swimming the fish before release, help reduce mortality rates. Satellite tags and archival tags are used to track the behavior of marlin and tuna, providing data on their location, depth, and temperature.

Tag recovery missions can be challenging, as the tags are small and can be difficult to locate in the vast ocean.

Bluefin tuna are endothermic fish, able to regulate their body temperature and withstand a wide range of temperatures.

Foraging hotspots and oceanographic conditions play a role in the feeding patterns and migration of bluefin tuna.

Collaboration with fishermen is crucial for successful research and fisheries management, as they have valuable knowledge and observations of the fishery.

The rebound of the bluefin tuna population demonstrates the effectiveness of strict management regulations and the importance of sustainable fishing practices, despite the many challenges that can be derived from these efforts.

Find Chloe on instagram at @coastal_chloe

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TRANSCRIPT

Katie (00:22.905)
Hey, what's up you guys? Welcome to the Katie C Sawyer podcast. I'm sitting here with Chloe Mikles, a remarkable young woman that I have been fan-girling over on the internet for years now. Chloe, thank you so much for being here with me.

Chloe (00:37.698)
Thank you so much for having me. Yeah, I feel like likewise, I've been fangirling over you for years too. So it's always fun to sit down and talk with you.

Katie (00:45.849)
That's so sweet. I really appreciate it. All right, you guys, Chloe is a PhD candidate at Stanford University, working with Dr. Barbara Block, a legend, studying bluefin tuna and blue marlin, movement ecology and population structures. Chloe, can you tell our listeners just like a brief synopsis of what that means?

Chloe (01:07.882)
Yes, so yeah, we oftentimes get caught up with like tossing in a lot of scientific jargon with our work. So Basically, I am in graduate school and for my dissertation work. I am learning from my advisor Barb Block and I am doing everything from going out into the field to tagging the fish which is the most fun part and probably what we'll talk the most about and then reading a bunch of papers to the scientific literature and

I do some lab work as well, and then it all ends up, the culmination of the PhD is basically writing a bunch of scientific papers that summarize our findings.

Katie (01:47.477)
So what kind of questions are you asking about these populations?

Chloe (01:53.258)
So you can start off like very, you can go from very simple to very complex, basically, these questions. The most basic question is, we're putting tags on animals to see where they go. And you can make that more and more and more complex. So for example, from Marlin in North Carolina, blue marlin have been tagged all over the world, but not that many have been tagged off the coast of North Carolina. So by focusing efforts regionally in different locations,

we can get a better idea of where the fish that pass through there go. And basically like if their migration patterns are different, if there are different populations of fish that are traveling elsewhere and just trying to learn more and more about these fish because it's so hard to study the ocean. I mean, it's not like, you know, a deer or a mountain lion or something where you can actually like watch where they go and track them or, you know, put a radio color on them and see where they go. The ocean is really hard to study. Everything's underwater.

Everything's innately then more cryptic. Um, the technology is much more difficult to actually get something that can track animals underwater. So the more tags that we put out and the more data that we collect, it's like, we're constantly learning more about these fish every single time.

Katie (03:07.065)
really love that you just like compared the ocean towards land mammals and land predators out there and animals that we've been studying and trying to manage for a long time. We still have so far to go to properly manage our wildlife on land and the ocean is that much more difficult to do. So we'll get into that a little bit a little later because I want to really touch on what you're doing and what kind of questions and answers we're getting from that. But for the sake of

Chloe (03:18.536)
Mm-hmm.

Chloe (03:22.764)
Right.

Chloe (03:26.322)
Exactly.

Chloe (03:32.415)
Yeah.

Katie (03:36.979)
I'm a blue marlin girl. Let's focus our energy on the bluefin tuna because it's just there's such fascinating animals and I have so many questions for you. So first off let's start with where you started. Where did you grow up?

Chloe (03:38.982)
I know. Cool. Yeah. Mm-hmm.

Chloe (03:55.074)
So I grew up in North Carolina and that is, yeah, that's a big reason why I've chose to study these fish for my PhD. So my family had a place on the coast of the Southern Outer Banks. And I just grew up there always being so fascinated by the ocean. And then kind of like in my most formative years when I was an undergrad and like right out of college, I made, you know, I made some of my best friends in my life and was fishing constantly. And...

that reason, like, I love animals. I have always been passionate about studying them. It probably could have been anything, but the fact that, like, in those years I became so obsessed with offshore fishing, that's, yeah, that really did it. I know. Yeah. So...

Katie (04:38.381)
I got chicken skin. I feel that. I feel that on so many levels. So you did your undergrad at Cornell, right? You had a, didn't you have a full ride scholarship swimming?

Chloe (04:51.17)
So I did swim there for four years. The Ivy League actually doesn't provide like athletic scholarships, which is interesting. Yeah, but yes. So I swam at Cornell for four years. I majored in animal science. My original plan was to be a vet because I loved animals. And then I was doing a couple of internships with North Carolina State University and their Marine Station on the coast, actually working with both like fisheries biologists and Marine veterinarians.

Katie (04:53.111)
No big deal.

Chloe (05:21.038)
And I was like, this is so cool. Like I didn't realize that there was a career where you can actually study the ocean. Like I was getting paid as an intern. I mean, not much, but I was getting paid as an intern to go offshore and tag Mahi. I was like, this is so much fun. This is so cool. Um, and then as far as bluefin tuna, um, I just saw firsthand how important that fishery was to the local community. And it was like this amazing seasonal thing where every winter,

Katie (05:35.441)
Yeah.

Chloe (05:50.994)
It's like everyone would be commercial fishing for them. Like you would get your hardcore commercial fishermen who fish all year round fishing for bluefin tuna. But then you would get people who just do different jobs, um, take off weeks to partake in the commercial bluefin fishery for a couple of weeks. And yeah, it's a really different, I think it's a very unique commercial fishery. It's very different from most places in the country and the world. Um, it's a very short season, but

Katie (06:07.493)
That's fascinating.

Chloe (06:19.934)
I saw how much money it brought in to the local community, how excited people were, like, you know, there'd be little kids coming to see the bluefin brought in. And it was just like this, and it coincides with, you know, Thanksgiving and Christmas. So it's like this holiday season, just an extra excitement to the holiday season.

Katie (06:39.013)
Definitely. Tell us a little bit. So there's three populations of bluefin. There's the Atlantic bluefin, the Pacific, and the southern bluefin, correct?

Chloe (06:48.806)
Yeah, so those are three different species. It gets very complex when you start, yeah. So there are different species of bluefin tuna and then they're within the Atlantic, there are different populations. So it can get very complex depending on, yeah. Mm-hmm.

Katie (06:51.294)
Okay. Okay, right.

Katie (07:00.261)
So, right? And the more we know, the less we know. So in North Carolina, you're fishing for, or the commercial industry is fishing for bluefin, the Atlantic bluefin tuna.

Chloe (07:08.508)
Yeah, that's the best way of saying it.

Mm-hmm.

Katie (07:19.129)
Tell me a little bit about the sizes of fish that are harvested and what the regulations are there. Like how many tags, what the release ratio might be, like give us a little bit of insight into that fishery specifically.

Chloe (07:19.211)
Yeah.

Chloe (07:25.302)
Mm-hmm.

Chloe (07:29.506)
Hmm.

Chloe (07:35.242)
Yeah, so specifically in North Carolina, well, actually just federally in the United States, a bluefin commercially has to be over 73 inches. So that's a pretty big fish. In North Carolina, it's a mixed size class of, I mean, you get fish probably as small as 50 inches and up to like upwards of 110. So it's a big range, but what's nice is you're not getting like a ton of the really little ones.

Like you might get off the coast of Massachusetts, or not really little, but smaller. Yeah, I don't know if that upset anyone, but compared to the giants that you get in Nova Scotia or, I mean, people in Massachusetts still get really big ones too, but you know what I mean.

Katie (08:10.021)
Careful.

Katie (08:16.263)
Right.

Katie (08:21.445)
Yes, of course, of course, yes. We love you Massachusetts. So 73, you said 73 inches is qualifies as a giant, correct?

Chloe (08:26.606)
I don't want to call anyone out.

Yeah, that's.

Um, yeah, I think so. I forget all of that. Noah has it all spelled out, but 73 inches to harvest commercially. Yeah.

Katie (08:36.069)
That's okay. We don't... Yeah, yeah. And how many tags or how many, is it a tonnage or is it like how much can be harvested in the season?

Chloe (08:48.678)
Yeah. So it's based off of quota. And what makes this a really tricky fishery for people also is that once the quota is met or they predict that it's about to be met, they'll close the fishery immediately, like effective, like tomorrow at midnight, essentially. So you really don't have a great idea. Like when you start, I mean, you can, you know, if North Carolina knows like, Oh, we're going to get 60 metric tons for December. Then people have a good idea of.

how quickly that will fill up, whether that's gonna be a week or two weeks, always depends on how good the fishing is, the size of the fish, the size classes that are coming through there. And then there's a limit of one per vessel per day.

Katie (09:29.837)
Okay, that's interesting. Really cool. So that's all fine and dandy. NOAA regulates federally in the U.S. But these are highly migratory species. So how does that work on an international level?

Chloe (09:34.974)
Mm-hmm.

Chloe (09:40.206)
Yeah

Chloe (09:43.506)
It's, yeah, that's the problem of the bluefin tuna and other highly migratory species is that they cross the jurisdictions of many different nations. I can't remember what the number is. I think for like all bluefin tuna, it's like over 50 different nations that are competing for this resource. So if you're a bluefin tuna, everywhere that you go, someone's trying to catch you. So in the Atlantic, they are managed by this international organization called ICAT.

um, which I'm going to blink on the acronym, the International Commission for the Conservation of Atlantic Tunas. And they manage, bluefin, thanks, um, there are so many different, across the world there, like seven different, they're called RFMOs, Regional Fishery Management Organizations, and they all have like, similar, slightly similar, but differing names. It's hard to keep them all straight, but they manage for the most part all the highly migratory species of their set region.

Katie (10:21.709)
You nailed it.

Chloe (10:43.562)
So they set the quotas for different countries and perform the stock assessments and do all of the complicated data analysis and politics.

Katie (10:54.373)
So the politics are done internationally, regulated internationally as well as nationally. But there's so many questions we still have about this tuna, which is why your work and Dr. Block's work and all the work at Hopkins is so important, correct? Now go for it. No, no, no. Tell me what you just say.

Chloe (10:59.11)
Right. Correct, yeah.

Mm-hmm.

Chloe (11:09.61)
Yeah. Mm-hmm. And it's, oh, go ahead. Oh, I was going to, it's really an international effort. Like, yes, we have our lab that's based at Stanford, but we are working with collaborators all across the world, from Canada to Spain, Italy. There's a country where bluefin tuna go, you name it. We've probably worked with them in some regard, as far as getting samples or tagging fish. So it's, oh, right. Yeah.

Katie (11:34.265)
That's awesome. I was able, and you know this, but I was in the Canary Islands with the On Location when Tag a Giant Foundation came over and we helped them catch fish to tag four-year studies and it was in collaboration with the University in Barcelona. So that was really incredible. I hope that you and I get to go do that one day. Have you been over there?

Chloe (11:42.306)
Mm-hmm.

Mm-hmm.

Mm-hmm.

Chloe (11:54.282)
Oh, mm-hmm.

Chloe (11:58.854)
I know. I haven't. It is my dream to go there. I want to go so badly. I'm gonna push for it this year. I have a lot of work to do. So unfortunately, like the further... yeah.

Katie (12:08.953)
You're in your fourth year, right? You're in your fourth year, so it's kind of busy, right?

Chloe (12:14.018)
Right, the further you get in the PhD, it's probably the more data analysis and the less fun in tagging, but hopefully I get a chance to get out.

Katie (12:21.913)
That's why they hook you early. That's cool. Okay, so let's go ahead and talk about the tagging. Let's talk about what these programs look like. I wanna know what Taggagiant's doing over in the Canaries and what they're doing in North Carolina and everywhere else and what we've discovered from them.

Chloe (12:24.035)
Yeah, exactly.

Chloe (12:28.12)
Mm-hmm.

Chloe (12:37.14)
Mm-hmm.

Chloe (12:41.758)
Yeah. So what's cool is basically everywhere that we go, we are working with the local community that's there. Like, we're in California. We can't just show up somewhere and pretend like we know how to catch bluefin tuna and just go off and be successful. Like, that would never work.

Katie (12:58.048)
I love the picture you just painted. That was perfect. Keep going.

Chloe (13:02.43)
So, you know, whether it's Nova Scotia or the Canaries or North Carolina, we're working with commercial and recreational fishermen in those locations who are the experts of catching bluefin in that spot. Like, you know, when you're in the Canaries, like, it's probably very different fishing than if you were in Southern California or if you were somewhere else. So, it's really special because I get to learn when I travel to these locations, all of the, you know, very regional specifics.

what everyone has, you know, their different superstitions and their different techniques and what they swear by and um here do I could you lose me I'm oh okay

Katie (13:37.397)
Oh no. Hold on.

I did lose you, but I think it might have been on my side. Oh shoot, let's start. I heard from regional specifics, so if you could kind of go a little bit back and we'll try again. Sorry.

Chloe (13:54.582)
Okay, no, you're good. Yeah, so when we travel to these different locations, we really just get to spend the time working with the commercial and recreational fishermen who all have these regional specifics of gear types and superstitions and things that they swear by. And it's a really cool opportunity to learn. And that's the reason that we're successful because we have the people that are experts for that region helping us tag the fish. So.

It usually requires a lot of complex permitting to make sure that we get everyone, you know, on the same page, but usually people are really excited and, uh, really helpful and people are just innately curious about these fish. And, um, for the most part, everyone's very happy to be a part of it. So it requires a lot of coordination, but, um, it's great cause we get to tag fish of different populations, fish of different age and size classes and

The goal for most of our work is to track these fish to their spawning grounds. And in the canaries, those fish are mostly going to spawn in the Mediterranean sea. In North Carolina, it's a very mixed batch. We get some that are going to spawn in the Mediterranean sea, some in the Gulf of Mexico. And then there's a spawning location that is, um, people are working really hard right now to understand better called the slope sea, which is

off the coast, basically north of Hatteras all the way to the Scotian Shelf. It's like this weird kind of like shape off the continental shelf and bordered by the Gulf Stream. So we've discovered that there are some fish spawning there. So the goal is to track these spawning fish and figure out where they're going. And to understand like, oh, in Nova Scotia, maybe we have

predominantly Gulf of Mexico fish, but maybe that's shifting year to year. So you wanna know which population the fish originates from to be able to better manage the stock. That's a hold.

Katie (16:00.197)
So, there are two, maybe three, maybe more populations of bluefin tuna in the Atlantic. One population is what you're dubbing the med population, and the other one is the gulf population. So, what you're saying is these fish consistently go back to their same spawning grounds once they're of maturity every year. Wow.

Chloe (16:04.942)
Correct, yeah. Right. Yes.

Chloe (16:21.214)
Mm-hmm. Yes, that's our understanding. And I mean, sure enough, we're going to get one day that goes to both and throws the whole thing out the window. But for right now, the understanding is, yes, that they're managed by ICAT as two populations, the Gulf and the Med for sake of simplicity. And they'll refer to that as the Western and the Eastern populations. So.

Katie (16:30.289)
I'm sorry.

Chloe (16:47.134)
Yeah, it gets, it gets complicated because then they're mixing in the middle of the ocean. But we do, I've been working on a lot of tagging data showing that they repeat, visit these spawning locations year to year, when we can have longer term tags on them.

Katie (17:02.297)
and you take little samples, are these populations genetically different?

Chloe (17:07.551)
So that is the question of my PhD. How did you know? So yeah, my PhD work is really aiming at specifically characterizing these populations from an ecological movement-based standpoint and also a genomic standpoint. So there have been a lot of different genetic markers used over the years to try to characterize and figure out how they're different.

from smaller subsets of genetic markers across the genome. People can say, oh, this one's Gulf, this one's Med, this one is maybe something in between, not really sure. So I'm using the whole genome of the animal to try to really increase the amount of markers that we can use to differentiate them. So yeah, so when we go out and we tag the fish, I will usually get a small thin clip from them and...

we try to get a fin clip and a muscle biopsy. And sometimes, you know, things are chaos on a boat and you miss them, which is too bad. But we try to do our best and get as many as possible. Yeah, exactly. So we get those and then I'll go and collect samples from fish that are landed also whenever I have the time.

Katie (18:10.413)
Because you have like a 600 pound fish on the deck.

Katie (18:22.993)
So, okay, for the listeners that might be like, wait, what is this? You're actually taking parts, parts of a living animal and putting it on the deck and that sounds horrible. You terrible person, Chloe. You're awful. Anyway, let's talk about the process and how, and how it's not at all terrible and what is, what, what type of measures you guys take to make sure that fish is as comfortable as possible.

Chloe (18:26.958)
Yeah. Right.

Chloe (18:36.974)
Yeah, the process.

Chloe (18:47.722)
Yeah. So part of it, you know, it all starts when you hook the fish. So we really try to use, always use circle hooks to maximize being hooked in the corner of the jaw. So that makes one thing easier. And then you also want the fight time to be as quick as possible. So we're not trying to be sporty about it. We're just trying to get these fish into the boat as quick as possible. When we get them into the boat, which is also a difficult process, we have to hook the fish basically in its lower jaw.

and pull it up onto the boat with a rope and it usually takes several people depending on how big it is. And then once the fish is on the boat we have it in this blue mat that you'll see in a lot of our pictures. And someone like hand sewed that mat for us a long time ago and I don't like that's not something you can just go out and buy like someone made it specifically for our work and has handles on it so we can turn the fish. But that protects the...

Katie (19:20.588)
Mm-hmm.

Katie (19:40.737)
Sorry, I'm laughing because I remember when Robbie showed up in Gomera with this hand-sewn mat and I was like, it was massive. And those boys, man, they were packing them up on the flight for the flight back and I was like, what are y'all doing? It was making so much noise. Anyway, continue with your mat. I interrupted you. It's just a fond memory I have. But it, talk about a little bit before you go on about the purpose of that mat.

Chloe (19:59.54)
No, you're good. Yeah.

Katie (20:07.429)
and sliding that fish onto the deck and the slime of the fish.

Chloe (20:08.614)
Yeah, mm-hmm. Right, so that's important, as you just said, yeah, to protect the fish's slime. And, you know, there's a lot of stuff, like the deck of the boat is made to be grippy so that we are not slipping around on it. When, you know, you have a mate in the cockpit trying to wire a fish, like, you need to have your feet be grippy on the ground, so, but that is really damaging the fish's skin. So, hence our mat. And then we stick a hose in their mouth to irrigate their gills.

So we're always checking like whatever boat we're tagging on, like I'm bugging the captain, like, Hey, is your hose a high enough pressure? Because we need a lot of water moving through this fish's gills. And then, um, because yeah, a fun fact about bluefin tuna and other, um, highland migratory fish is that they have to be moving forward to breathe underwater. So they use, as you're familiar with a process called ram ventilation, which is like the literally need water being pushed through their mouth.

to irrigate their gills. So if you stop them, yeah. Yes. I think, yeah, some species of sharks. I'm not a shark expert, but I don't know. But yeah, bluefin and blue marlin for sure and other tuna species. So, and they're the ones, you know, they're moving fast essentially. So if you stop those fish,

Katie (21:08.845)
Same with billfish, sharks, correct? Mm-hmm. So if you stop them.

Okay, yeah. Let's not go there. Go on. So if you stop at tuna...

Chloe (21:33.95)
it would be very hard for them to be breathing. So that's why we put the hose in their mouth. And then we put a cover over their eye just to protect their eye. I mean, they could be looking around and seeing what we're doing. They're honestly like too big to move around while we're doing anything for them. Like when you put this big fish on the deck, it's usually not big enough to actually like lift its tail up in like, you know, gravity is a much stronger force than they're facing in the ocean when they're moving. So they usually can't lift.

their tail up that high to start doing like the tuna slap on the deck that you see like smaller ones do. Right. And then, yeah.

Katie (22:09.073)
the smaller ones yeah. I thought the I thought the towel over the eye was to keep them calm to keep it dark and kind of just

Chloe (22:20.142)
Maybe. Yeah, I mean, protect their eye, keep it. I mean, I don't really know if we didn't put the towel on their eye if they would be less calm. We could test it, but it's just something we always do. So maybe. Yeah.

Katie (22:31.46)
No. Yeah, of course. It's like a spa day for the comfort of the fish, my bad.

Chloe (22:38.386)
They're being abducted by these human scientists and probed and then sent back into the ocean. I would love to know what they think. And then while the fish is on the deck, we get a couple measurements. So we get their curved fork length, their girth, and then I take a fin clip, a muscle biopsy, we stick the tags in. We also put a spaghetti tag in the fish that has a phone number to call.

Katie (22:40.578)
Ha!

Chloe (23:05.418)
So those, I mean, a lot of people in tournaments are just for fun, we'll go out and spaghetti tag fish. And that'll be really valuable information for a point A to point B. So we have that as an identifier on there. Usually one sort of electronic tag. Sometimes fish get two tags. Um, and then we turn them around and set them back. And because we're tagging them with electronic tags, we actually know what happens to the fish. So if the fish were to die, which

for the most part does not happen. I mean, it's very rare. I'm not gonna say it never does. Every once in a while, unfortunately, one dies, but we know and we report that right away. So that's part of the research. Like if a fish weren't to make it, which rarely happens, the tag actually pops off of the animal. So there's a sensor on there that basically, if it sinks to the bottom and it doesn't move for three days, then the tag pops off.

Katie (23:40.741)
science.

Chloe (24:04.47)
But the great thing is that doesn't usually happen. So we know that the fish, yeah. Right.

Katie (24:07.033)
That's crazy. So you don't have to wait the 360 days of the tag life. It's just, it lets you know immediately.

Chloe (24:16.498)
Yeah, we're usually just like, I mean, just for the, you know, we always like hold our breath for a couple of days. And we're like, if we haven't heard from it, then it's good. The fish is moving. It's somewhere. Like, you know, I was, I tagged my first blue marlin last year and I was just like hoping, hoping I was like, this is my first one. Like, I hope it's going to be okay. And, um, you know, also that I placed the tag correctly and it doesn't pop off of the animal and then if you don't hear from it, exactly. Yeah. These.

Katie (24:41.349)
That's an expensive mistake.

Chloe (24:45.398)
The satellite tags are like four or $5,000 a piece. So it's nerve wracking. Yeah, you wanna make sure that it goes well. Right, and then for that part, we're also taking as good of care of the fish as possible. Like if a fish comes up on the boat and it's like a seam or comes up to the boat, usually we don't bring it on the boat if it looks stressed. You know, like if the color is off, if it doesn't look good, if we ever accidentally get a tail wrapped fish, God forbid that, like we cut it loose, let it go, try to swim it to get it moving again.

Katie (24:51.157)
It's super, it's a lot of pressure.

Chloe (25:15.398)
and we're not going to put a fish that isn't in great condition through the stress of tagging.

Katie (25:20.729)
Yes, so for the listener, Chloe just mentioned if we ever get a tail wrap fish. We were talking earlier about how tuna and a lot of pelagic species need to be moving forward to breathe. So if you get your fishing line wrapped around the tail of the fish, you're going to end up pulling it from the back, backwards and then pushing water through the gills in the wrong direction. So that's how they asphyxiate. But there are ways as an angler and a captain to help mitigate these issues and make sure that they don't happen.

Chloe (25:23.31)
Mm-hmm.

Chloe (25:29.803)
Mm.

Chloe (25:38.572)
Right.

Chloe (25:42.754)
Mm-hmm.

Katie (25:50.663)
if they do happen to address it early and make sure that fish lives through the process. Now we'll get into that another time but I just wanted to touch base on why tail wrapping is such a bad thing. Now Chloe what I find fascinating is that these bluefin tuna and other tuna are so stout they're so sturdy and they can take that type of

Chloe (25:59.49)
Mm-hmm.

Chloe (26:04.15)
Yeah, thank you.

Mm-hmm.

Chloe (26:16.322)
Mm-hmm. Right.

Katie (26:20.661)
I don't want to say harassment, but that type of, um, what's the word I'm looking for? Yes, yes, and, and then live on it happily. I mean, like you, like you said, the science shows, the data shows. Now, I said we weren't going to talk about blue marlin, but Bill Fish, you don't take them out of the water to tag them, do you?

Chloe (26:24.241)
Stressed, yeah.

Chloe (26:31.155)
Yeah.

Chloe (26:38.505)
Yeah.

No. So billfish are considerably more fragile than bluefin tuna. And like the smaller billfish, like spearfish and sailfish are very, very fragile for whatever reason. Those fish, like, you know, in the States and I can't remember if other countries, but in the States, it's illegal to pick one up out of the water unless you're going to harvest it. So those fish, you want to

Chloe (27:11.074)
For pictures sake, you know, the GoPro stick was invented and people have found a way to like get a great picture shot of a sailfish next to the boat without having to bring it out of the water. Yeah. Exactly. They die, right?

Katie (27:21.209)
So much prettier than when they take them out of the water. They get all dark, they're ugly, and then most of the time they die. But in the water, they're properly aerated, they've got all their beautiful colors. So definitely encourage the listener, if you guys go bill fishing, to keep your fish in the water and take a picture that way. But Chloe, how do we know that they don't survive and why has it become legally mandated to keep these fish in the water?

Chloe (27:31.566)
Right.

Chloe (27:44.158)
Mm-hmm. So there have actually been a ton of scientific studies evaluating catch and release mortality. So that's basically the percentage of fish that are caught angled a certain way and released. So there's a huge body of literature and a lot of scientists that work on that question and so many different species. And you can get very, very specific with it. You can have a certain, like there are different, basically more catch and release mortality estimates for.

every single different species and every different way of capture. So you'll have someone evaluating light tackle catch and release mortality on, um, blue marlin or bluefin tuna or the same, you know, the same for any other species. And you're really trying to estimate like, okay, what can we do to minimize, um, mortality for these fish? And a lot of times it's, um, quicker fight times, limiting air exposure, limiting handling, um,

It's things that all like kind of make sense when you spend a lot of time out on the water and you see how these fish react. But you know, it's like when I first started trout fishing, I was like, wow, trout are super fragile. Like you know, you fight those fish too long and they like can't even swim again. So ocean fish in general are more are a lot tougher. But yeah, we don't bring I think that some of the earlier studies with blue marlin, maybe they think.

Katie (28:55.513)
Yeah.

Chloe (29:10.73)
At some point people probably were bringing them on the boat and then they were seeing from the tags that they just don't survive. Or if you don't swim the fish when you're releasing it. We found from a lot of tagging work that if a fish is really tired after tagging it, you really need to take the time to swim it and release it. That practice thankfully is caught on widely in the whole bill fishing community and I see people having those videos. Because everyone wants that video of showing that your fish swam away.

Katie (29:33.474)
Yes.

Katie (29:39.633)
The healthy release. Yes, we're not out there because, exactly, we're not out there because we don't like them. So no, they're incredible. We always swim, especially our big fish, we always swim our big fish. And you can tell, like I mentioned earlier, the coloring of the fish helps show how healthy and the lack of color shows the level of stress. So how do you tag your marlin?

Chloe (29:39.766)
We all care so much about these fish. Yeah, we don't want them to die. Ha ha. Right. Mm-hmm.

Chloe (29:57.249)
Right.

Chloe (30:02.123)
Mm-hmm.

Chloe (30:06.006)
So yes, the marlin, it's a huge coordinated effort between captain, mate, or mate's plural sometimes, and whoever's tagging the fish. So usually, it depends on whether you're tournament fishing or what, but usually the captain will try to back down on the fish quickly to minimize the fight time. And then as long as the fish isn't too green, like you want it to be somewhat under control also. So it's a really fine balance. Like.

Katie (30:33.029)
Green is not a color, it's a behavior.

Chloe (30:35.47)
Green is a behavior, yes. Thank you. So you'll have a fish, you know, you can't safely tag a fish that is still jumping and tail dancing across the water. You need it to be somewhat under control, but not too tired that it's like having a hard time moving. So it's this really fine balance. And then, you know, it requires the mate to get it close to the boat. And then we like to place the tag right under the dorsal fin.

And I think I sent you some pictures that we can show listeners later, but that is like the spot where you want to tag the fish to help like it's above their lateral line, which is a really cool sensory organ that we can talk about later. Um, but you want it to be like deep into the muscle. Um, but then like it's, you really have to avoid like damaging any specific organs. So it's like kind of in the shoulder of the fish, I guess. Um, and then it's in the spot that.

Katie (31:06.149)
Definitely.

Chloe (31:32.562)
really minimizes any sort of drag also. So we don't want this tag, you know, and we also don't tag small marlin. We only tag ones that are big enough so that the tag actually isn't interfering with their, or minimally interfering with their day-to-day activities, swimming life. So it can be hard because like you'll get a fish next to the boat, a marlin, and the mate's holding on as hard as he can trying to get it in the right position and the fish is just like rolling over like belly up.

Katie (31:50.26)
I love it.

Chloe (32:02.326)
You're like, well, I need you to be sideways so you can get the tag in on the side. Right. So it can be very tricky to keep the fish in the right position. Yeah. And then we have a long tagging pole that AFCO makes that we, uh, is super easy and lightweight and you can just stab the tag into its back and let it go on its way. Yeah.

Katie (32:02.335)
Yeah.

Katie (32:05.785)
Give me your dorsal!

Katie (32:12.601)
That's... yeah.

Katie (32:25.765)
Let it go on its way. Awesome. Switching gears back to Bluefin. Let's talk, and it's the same thing with these blue marlin tags too, but I really wanna focus on these tuna of yours. What all do the satellite tags, what type of information do they gather, and how does that information get brought into the day by day of the fish? Like telling us about the day by day of the fish.

Chloe (32:31.062)
Yeah.

Chloe (32:34.998)
Mm-hmm.

Chloe (32:49.694)
Yeah. So the satellite tags, I wish I had one to show you, but it's basically this. Yeah. So the satellite tag is this waterproof pressure proof package that contains a computer chip inside a battery, all of these different sensors. So start from like the top of the tag. It has a light stock that is measuring the light levels.

Katie (32:56.249)
We'll show it on while you're talk.

Chloe (33:16.734)
And from that, we can actually mathematically geolocate where the fish is. So we know when the sun rises and we know when the sun sets and we use different mathematical algorithms based off of that to position the fish. So that data all gets stored inside the tag. Then we also have an external temperature sensor that's sensing the environment around the fish, the water that it's in. So when it's diving deep or on the surface or travel anywhere, you can get the temperature of where the fish is.

And then there's a pressure sensor, which you can calculate depth from. So as you go down, pressure increases and we can determine basically to the exact meter. Science uses all metric, which makes things complicated going back and forth, but we can figure out exactly the depth of fish is swimming at. And then, so that's a satellite tag. There are also, I can talk more about later, archival tags that we surgically implant in their bellies. And the only difference between those is,

The archival tags also have an internal temperature sensor, but then they also stay with the fish for life. So the satellite tag is this package that detaches from the fish after a pre-programmed time. So in its computer sensor, and depending on what sort of experiments we're doing, we'll set that time differently. So you can set it to pop off after a couple of days, after a week, after two weeks, you can set the exact number of days, but usually we set them to a year, or as long as we can.

So the battery life on those lasts about a year. We'll pop the tag off and then it actually starts transmitting its data up to the satellite. And it just starts like dumping the data up to the satellite as fast as it can before it dies. What's great is that if we get the tag back, we get the entire record. So when the tag is uploading all the data to the satellite, it's not able to get like everything at the sampling rate that it's taking. So.

It might be recording a data point every 10 seconds, but that's too much data to send up to the satellite. So it'll send like a shorter summary. Like maybe you have something like every minute or every couple of minutes, a position, a depth, a temperature. Um, so it just depends on the resolution of the data. I can keep going. Yeah. There's a lot to it. It's.

Katie (35:33.669)
That's amazing. So yeah, no, wait, I'm like, I'm kind of blown away about the fact that it records a data set every 10 seconds for a year. Like...

Chloe (35:42.658)
Mm-hmm.

Katie (35:43.885)
That's a lot of data, but then this concept of, you know, wherever the bluefin tuna is 360, 65 days later is where the tag's gonna pop up. So then you have this little tag that's gotta be like what, six inches long, maybe eight, that's floating around in the ocean and it's like, good luck scientists, come and find me before I die.

Chloe (35:46.27)
Yeah. Mm-hmm. Right. Mm-hmm.

Yeah.

Chloe (36:00.991)
Yeah.

Mm-hmm. Yeah. Exactly. And usually, right, usually they don't pop off anywhere convenient. Like, they're not going to pop off like right in your backyard. I mean, one did once, which is great. But, um...

Katie (36:13.515)
I'm sorry.

Katie (36:18.563)
That's awesome.

Chloe (36:21.986)
Blue Marlin that I tagged last year just popped up right off the coast of Belize, which was super exciting. So Robbie, who you know, flew down to Belize to try to go get it, and he went on this tag recovery mission. And as soon as he got out on the water, the tag died, and he could not find it. And it's just this tiny tag floating in the middle of the ocean. And I mean, with ocean currents and weather patterns, yeah. So he never found that one, unfortunately.

Katie (36:28.645)
That's awesome. Mm-hmm.

Katie (36:46.969)
You do what you can.

Chloe (36:51.882)
Maybe it'll wash up on a beach. That'd be great.

Katie (36:51.911)
Have you gone on...yeah right. Have you gone on tag recovery missions?

Chloe (36:58.562)
Yes, they are difficult. So you're looking for this little black tag that's barely floating in the ocean. So it's hard because you have so much. It's a mini computer that you've then, you know, made waterproof, made pressure-proof, and made like able to fit on a fish. And then you also need it to float. So it barely floats. Like it's just barely sticking out of the ocean, sometimes bobbing up and down.

and it has this little antenna that's kind of swaying back and forth, but it's black. And anyone who's been out in the ocean, like if you drop something black, it floats. Like it's not bright, but that's because we don't want other fish to be picking at it. So if it was a bright color, it's just kind of this fish swimming around and it might get bitten off by another animal. So that's why we make them dark. But we use this device, it's called a goniometer. And yeah, I know.

Katie (37:39.002)
Right.

Chloe (37:55.138)
Don't ask me how it works. It's like an omnidirectional stick that you put the code in of the tag and it tells you like it's like a game of hot and cold. Like you're getting warmer, you're getting further away. And once like I, the first tag recovery mission that I did by myself, I went with my friend

Katie (37:55.341)
I'm in. I'm into it.

Chloe (38:23.178)
And he was like, oh, we use that in the Marines to like locate stuff. It's like, great. Like, so maybe you can help me. Um, so we go off, yeah, looking for this tag, playing this game of hot and cold. You know, sun's going down, weather. Like we had like a very quick weather window and we literally, I have a picture of the tag in the ocean with the sun, like halfway set in the background. And it's like, we barely, barely got it. Yeah.

Katie (38:30.521)
Super.

Katie (38:49.822)
Oh my gosh. You got it. That's awesome. Is that the only one you've been on?

Chloe (38:57.016)
So I have helped get some in Nova Scotia also. Those are actually a lot easier because the fish usually returns to the Gulf of St. Lawrence every year. So we know that it's gonna pop off there. And then it's a big bay. You know, like there isn't the Gulf Stream to whisk a tag off. Like if you don't get a tag in North Carolina within a couple of days of it popping off, it's in the Gulf Stream and it's like on its way to Spain.

Katie (39:15.741)
Right?

Katie (39:22.307)
It's gone.

Chloe (39:23.658)
Yeah. And it's dying, yeah. Yeah. You still get a great amount. So you can tell basically the entire track of where the fish went. And then you get a pretty good summary of, you can get like a good average of the depths and temperatures that the fish likes to be in. So for marlin, we know that they really like to be, they're more surface oriented, they like to be warmer.

Katie (39:26.199)
And it's dying. But you still get, you still get, okay, so how much, if you don't recover the tag, how much data do you get back? Okay.

Chloe (39:54.178)
The bluefin tuna can go a lot colder. The bluefin can go, it's, it has like, it can withstand probably the coldest temperatures of just about any highly migratory species. They're amazing fish. And then we have them going down to the lowest temperature is zero Celsius, which is like freezing basically. So yeah, they're cold. They're warm fish, which is, so they are...

one of the only endothermic fishes. And of, you know, yes. So, I mean, we call it regionally endothermic, but they are warming their core up. So it's this really cool process where, you've probably seen when you like cut open a filet of fish that there's red muscle and white muscle. And in like, I'm trying to think of another good example, in just like a normal fish.

Katie (40:26.661)
fully endo.

Chloe (40:51.83)
The red muscle is on the outside, but in the bluefin tuna, they've basically like evolutionary evolved to internalize their red muscle. So that, so when they're swimming, they're heating themselves up. And then because it's internal, they're able to like insulate their body, retain that heat. And then through a series of their like countercurrent heat exchangers, which is like this very fine capillary network within their body. They're able to retain the heat.

inside. So it's this very, yeah.

Katie (41:22.661)
So is that why tuna meets red?

Chloe (41:26.87)
Um, the meat is really red because it's really concentrated with, um, myoglobin or, yeah. No, I was like, wait, is that correct? So, um, they, they have a lot of, you know, because they're, it's a highly efficient fish, they have a ton of mitochondria and their muscles just like packed full of those and all the oxygen transport. Yeah. It's physiologically they're like.

Katie (41:33.425)
Okay. Yeah. Sorry. Didn't mean to interrupt you. You were on a roll and I was just, I was kind of blown away. Sounded really good to me.

Chloe (41:56.29)
They're a very, very fascinating animal. And that's why my advisor, Barb Block, has really fallen in love with them. Like her, by training, she's a physiologist. So these animals are like one of like the world's physiological wonders, basically, that they've been able to evolve this system that's more mammalian-like. Like we are endothermic. We, you know, can adjust to different temperatures, but fish and reptiles are not. They just kind of, for the most part, they just go along with whatever temperature it is. And...

That's why you get iguanas falling out of trees in Florida when it gets too cold, because they just can't withstand that.

Katie (42:34.541)
Um, what about like yellowfin and blackfin and big eyes? Are they all endothermic as well?

Chloe (42:35.146)
Mm-hmm.

Chloe (42:41.366)
They are, but the bluefin has basically the greatest capacity for endothermy. So they also have similar systems. They're just not basically as strong and developed and evolved as the bluefin.

Katie (42:53.557)
And you were saying earlier, back when you were talking about the populations, you got your Eastern and your Western population and how they're all congregating, seemingly, off the coast of the Midwest of the U.S. And, sorry, Mideast. Mideast of the U.S. Northwest, thank you. Eastern land.

Chloe (42:56.722)
Mm hmm. Yeah. Mm hmm. Yeah. Mm hmm.

Chloe (43:08.658)
Mid- yeah. Northwest Atlantic Ocean. Eastern- yeah, it's- I always get it mixed up. Depends on whether you're talking about the continent or the ocean. Yeah. Northwest Atlantic Ocean is what we usually say. Yeah.

Katie (43:20.247)
Right. Thank you. So.

Thank you. Okay, so how they're all congregating in the Northwest Atlantic Ocean. And what just kind of blows my mind here, and that I really want to emphasize is the fact that these fish are crossing the ocean. And that's not a that's not common. Like even for blue marlin, like it's not common for them, as far as we know, to be crossing the ocean basin. So what does that mean? And how do they?

Chloe (43:39.171)
Yeah. Right. No. Mm-hmm.

Chloe (43:48.351)
Right.

Katie (43:51.117)
Like, do they feed in the middle of the Atlantic? Are there feeding points there? Like, what do we know based on your tagging research that these fish are doing to cross the ocean, and why is that so exceptional?

Chloe (43:53.495)
Mm-hmm.

Chloe (43:58.699)
Yeah.

Chloe (44:03.522)
So yeah, first of all, it's just a very far distance. So yeah, being able to make that migration and of itself is just incredible. We definitely know that there are foraging hotspots just about everywhere. We recently, I don't want to say discovered this spot. I mean, it's this oceanographic condition that we spot that we always, people always knew was there, but we didn't really understand why the fish were there. There's a spot like kind of in the middle.

of the Atlantic Ocean. And there's this eddy called the man eddy that one of my colleagues just published a paper on explaining how the fish are basically drawn to this eddy and that they're feeding on congregations of baitfish. We don't know what the fish are that are there. I'm sure someone knows, but there's like this big feeding aggregation for bluefin tuna that they all love to go to. And it's just this spectacular thing.

before I just kind of looked at the track and they're like, oh, it's just passing through, this must just be somewhere. But we actually see fish year after year returning to that location. So they know that there's some really high quality forage there and then, you know, so there are spots where they can feed as they cross the ocean. But sometimes you'll see tracks where it's just going very quickly and not spending a lot of time diving or, you know, just spending a couple of days passing through a very long distance.

So we can get a really good idea whether or not a fish is actually utilizing, like performing feeding behavior and diving or just swimming.

Katie (45:40.165)
So what are the, like, that's really interesting to me because when you're looking at this data that you're getting from your satellite tag at the end of the year, how do you know what identifiers are there that's showing you that fish fed in that location and what identifiers are showing you that it was just passing through?

Chloe (45:49.292)
Mm-hmm.

Chloe (45:56.45)
Mm-hmm.

So one really cool thing, well, okay, yeah, with the satellite tag, it's usually diving behavior. So we really think that the fish is only diving if it's going to feed or if it's trying to avoid predator, or sometimes they're diving to avoid surface currents. But that we really would have a very hard time understanding. But for the most part, they're only diving to feed or to avoid a predator. So yeah, that would be the way. A cool thing about the archival tags.

is with the internal temperature, you can actually get, you can actually know exactly when they're feeding because when we eat, our body actually warms up. It's called this heat increment of feeding. So when you're ingesting, taking in these calories, that's energy and your body as it's processing that is heating up. So we can actually, there have been some papers showing this with mostly smaller bluefin tuna. You can tell when they like take a bite.

their internal body actually cools down at first because they're getting cold water from the outside or maybe a cold sardine or something. And then it starts heating up as the fish is digesting that meal. And there's this curve of digestion and then it goes back down to baseline. So yeah, you can get this whole study of metabolism in the way that a lot of like human physiologists can also do in a wild bluefin tuna, which is just spectacular.

Katie (47:25.157)
Spectacular. That is fascinating. And with these with these archival tags, not only do you have to catch the fish again to get it back, but you have to like harvest the fish to get it back. What how many do you all set? How many archival tags do you all set out launching a year? And how many have you gotten back in your career?

Chloe (47:26.782)
Yeah. Right.

Chloe (47:45.602)
Yeah, so, oh man, it's, well, I think it's actually worth standing beyond my career. So since I've been putting out archival tags, I haven't gotten a single one back. Um, it takes a long time. So, yeah, not yet. Um, so I'm actually working on tagging data from an archival tag that was placed in a fish in North Carolina in 2012. And it is like the most remarkable. Um.

Katie (47:58.411)
Yet.

Chloe (48:15.358)
study of animal migration. And we've tracked the fish for six years and the battery life on the tag lasted for six years and it was caught in, um, like a pen in the Mediterranean sea and then harvested. So we were actually able to get the tag back. But, um.

Katie (48:20.529)
That's amazing.

Katie (48:29.413)
That's the Almadrabah, right? The Almadrabah fishery in the Med? Do you know about that?

Chloe (48:34.274)
Yeah, I'm not... a little bit. There's... yeah, I've never seen all of it.

Katie (48:37.153)
It's just like a big cultural thing in Italy and Spain. It's old, it's ancient practice of harvesting these fish in pens, but it's pretty spectacular. Yes, but sorry, continue. So that fish was harvested in the Med.

Chloe (48:44.055)
Mm-hmm.

And then Matanza, yeah.

Chloe (48:51.594)
Yeah. Yes. And so over time, it's really a product of like how many fish, how many we get back or how many tags we put out and then how many fish are caught. So if quotas are really low, we actually won't get that many tags back. If quotas are really high and we put out a lot of tags, then over time, so like starting in the late nineties, and if you give it a lag of about

20 years, we'll get close to about like between like 30 to 50 percent of those tags back, which is a huge return rate. Yeah. Like in fisheries literature, like I think a tag return rate of over three percent is considered to be like great. Yeah. So a lot of these fish are getting, yeah, and a lot of them end up getting caught in the Mediterranean Sea, and but this also requires

Katie (49:30.501)
That's... Yeah, that's a lot.

Katie (49:41.881)
success. Yeah, that, I mean, that's wild.

Chloe (49:51.734)
partnerships with the harvesters there so that they know like if there's this weird thing in the belly of the fish like they need to be aware that is something that they need to look out for and that they need to return to us. So it requires again this international collaboration and cooperation and people being supportive of the research also because you know people are like all these darn scientists you know I'm just going to crush this tag and throw it overboard then all the effort is done for nothing you know.

Katie (50:14.698)
Ha ha.

Chloe (50:20.442)
have to maintain those good relationships.

Katie (50:22.965)
And you touched on that earlier about how most people are really excited to have you guys on board and are just genuinely curious about the science and the studies. Have you worked with a lot of commercial fishermen and a lot of recreational fishermen? I want to hear a little bit about your stories with that.

Chloe (50:29.441)
Yeah.

Chloe (50:32.66)
Mm-hmm.

Chloe (50:40.254)
Yeah, so I mean, my best friend from back home, Natalia, who we both know, she, yeah, she is this badass commercial fisherman, fisherwoman. Um, and I learned so much from her about bluefin tuna and just fishing in general. So having that relationship. Yeah. I mean, I, that was, I learned more about bluefin than I feel like most scientists get to, because I was on the water fishing for them.

Katie (50:45.361)
She's incredible.

Katie (50:56.185)
God, that's so cool.

Chloe (51:07.57)
learning firsthand from the people that know the most about them. Because if you're out in the water catching these fish every day, like, maybe you're not a trained scientist, but your observations are all scientific. Like, you know, the great currents, the right tides, the right temperatures, you know, the seasonal migrations of them, when they go, where are they going to be and when. So, you know, exactly right. What they're eating, how to present the bait properly. Like fishing is so scientific in nature. So.

Katie (51:27.341)
what they're eating, what to look for, and all the conditions.

Chloe (51:36.938)
I mean, that's why I feel like I was so drawn to it. Cause I was like, wow, this is like, this is scientific. This is really cool. So for the most part, like fishermen know best where the fish are, what's going on in the fishery. Like if they're the ones that you need to go to, I mean, they know best. So I've been really lucky to have these good relationships and you know, the fishing world is so small. So.

you know, you make one good connection and then, you know, you can go just about anywhere in the world and there's someone who knows someone who knows someone who can connect to you and that goes a long way. Um, and it's right. Exactly. So, you know, every once in a while, of course you're going to meet someone who's grumpy and not excited about the tagging and the science. And that's probably cause they've been around for a really long time and they've seen how the fishery changes and

Katie (52:16.257)
and is so happy too.

Chloe (52:34.198)
You see a lot of things where it's like, oh, it's not like it used to be. Like the fishing was so good back then. But in the case of bluefin, I feel like a lot of people are seeing now how, you know, there were, there's been like the most strictly managed fish in the world. But your people are seeing in their lifetimes, the fish, the fishery rebounding and they're seeing, oh, wow, we're actually seeing more fish in our waters than we were like 10 years ago. Or maybe this year is bad, but.

last year was really, really good. Or maybe that we see a lot of small fish that we know are going to be around and be bigger in the next couple of years. So it's cool. I feel like people have really been able to see like, you know, that fisheries being closed down and management being really strict isn't like, I mean, it's not, it's very contentious. It always is between commercial and recreational fisheries and being a fisheries manager would be a really, really hard

Chloe (53:32.682)
the effects of it and when it does go correctly, when the science, when it's incorporating all of the science, when it's incorporating, you know, the data that the fishermen are collecting, that's all like the catch, you know, that people are reporting that commercial fishermen are required to log their effort. Those things all go into the stock assessment models, make it more precise and that data helps to, you know, provide better management. And that's.

what our science is trying to do. We're trying to provide the best possible data to managers so that they can adequately manage the fishery. Because I mean, we want there to be more of them. We want, you know, fisheries management is by nature economic also. So it's, you know, NOAA fisheries is housed in the department of commerce. So this is an economic resource, not just a really fascinating ecological and animal resource, like it's a wild population that's economically important.

Katie (54:29.837)
It's significantly both for the commercial sector, but also for all the communities that depend on them and for the tourism sector of those communities. So I really like that you just touched on a ton of different stakeholders in this conversation about the...

Chloe (54:29.842)
So if we wait, yeah. Yes.

Chloe (54:37.433)
Exactly. Yeah. Mm-hmm.

Chloe (54:44.854)
Yeah.

Katie (54:49.305)
fishery and the commercial fishermen and the recreational fishermen and the science scientists and how this population has rebounded. And let's hear a little bit about the rebound of this population. Before I get into my closing statements, I just I want to ask you a million things, Chloe. So I think we're going to have to do another podcast episode. I know I don't know where the time goes. I know we're going to have to do it again. But but I want to hear just a brief bit about the rebound.

Chloe (55:04.352)
Mm-hmm.

Chloe (55:08.43)
Oh my gosh, it's already 1058! What? Oh my gosh. Well, yeah.

Katie (55:19.882)
and then we'll get into some closing statements.

Chloe (55:23.278)
Wow, that went so fast. So, oh gosh, I'm gonna get all the dates and decades wrong, but basically the bluefin fishery started crashing in the 70s and 90s, and then there was like, it was, there was a petition to list it as endangered on the CITES endangered species list, that didn't happen. But the population was...

You know, we saw just like year after year from the stock assessments or not. We, I wasn't around the stock assessments were showing the population was decreasing each year and the amount of fish that were making it back to breed and spawn were decreasing those fish weren't producing anymore. So, um, they're really strict, um, management regulations for a long time. And I don't know specifically what those were, but the bluefin tuna, they don't reproduce until they're about 10 years old. So.

Katie (56:18.829)
so old. That's so old for fish.

Chloe (56:20.234)
The hard thing is, like, you have people who are very frustrated, who are like, I've been patient, like, I've been, you know, listening to these rules for so long and I'm not seeing any difference. I'm not like, of course you're not because the fish doesn't reproduce for until it's 10 and then that fish doesn't really recruit up into the fishery until it's about five or six years old. So.

It takes a really long time to see the effects of management and also for management to know if what they're doing is actually effective. So it's a really tough balancing act. Yeah.

Katie (56:53.965)
It's a tough balancing act for everyone. I feel like for the communities that are depending on the fish, but also for the scientists to be standing by their decisions and the rule makers for to be standing by their decisions because like you said, ten years, that's so... In the world of fish, that is so old. And how old do these fish get? Generally.

Chloe (57:00.26)
Right.

Yeah.

Mm-hmm.

Chloe (57:10.507)
I know.

We estimate that they can get as old as 40. So I know. But probably most of them are caught or eaten by something else before they get to that age. So it's a fish eat fish world.

Katie (57:16.933)
WAAA

Katie (57:26.029)
Right. Fishy fish world. All right, Chloe, that was an incredible conversation. I could go on forever with you. It's amazing. I didn't even get into the Gulf of Mexico. So we'll have to do another one on that one. But I do have a couple questions for you closing up. For any listeners out there, like younger listeners that are interested in what you just spoke about, or, you know, understanding, even if it's from fish to...

Chloe (57:34.038)
Yeah, same. Yeah.

Chloe (57:43.394)
Sounds good.

Katie (57:53.797)
birds. I know that you're a big bird girl too. Studied ornithology, right?

Chloe (57:55.731)
Yeah.

Chloe (57:59.858)
Yeah, I did some work with the Cornell Lab of Ornithology as an undergrad and studied lots of different birds there. So it was cool. It was a lot of fun. Yeah. Thank you.

Katie (58:05.229)
that you're seriously one of the coolest people I've ever met. So, do you have any words of advice for young listeners that are that are fascinated by this conversation and want to get into a field of science or you know what are some words of advice?

Chloe (58:19.767)
Mm-hmm.

Chloe (58:25.93)
Yeah, I think that the most important thing is to really like follow your passions and stay true to yourself. Like don't pretend to be someone else just to try to, you know, fit into a certain mold. Like really play to your strengths. Like I mean, everyone has strengths and weaknesses and we can always try to like, you know, bolster up our weaknesses, but just play to your strengths and just don't close the door to any opportunities. You know, like if you get

a really incredible opportunity to partake in something. So like, even if you don't know if you're going to love it, just try it. Because the worst thing that happens is like, Oh, maybe you don't have a great time or you realize like, Oh, maybe like working on fishing boats and collecting this data, like maybe that's not for me. Um, so yeah, exactly. Um, and it's really just about like building your network, like professionally and personally. I mean, it's just, you want to be doing what

Katie (59:09.785)
But I did meet this one cool person.

Chloe (59:24.082)
you love doing. That's the most important thing, like getting through the like, especially doing a PhD. It's a long time. And it's difficult work. So you have to really, really love it. Yeah, I think that sums it up.

Katie (59:37.197)
I love that. That reminds me of, I think it's Mark Twain quote where he says, there's the two most important days in your life are when the day you're born and then the day you find out why. And I just love that. Yeah, it just follow your passion and pursue what really sets your life on fire.

Chloe (59:45.995)
Mm-hmm.

I'm sorry.

Chloe (59:52.414)
Oh, I love that. Yeah. Mm-hmm. Yeah.

Katie (59:58.301)
I think that's really cool. You are an incredible role model for so many people out there, young and old, male and female. I just think what you're doing is absolutely amazing. I really appreciate your time today and I can't wait. We're gonna have to get back on a podcast and talk some more because this could go on forever. You're incredible.

Chloe (01:00:04.654)
Thank you.

Chloe (01:00:15.658)
I know. I can't believe an hour flew by that fast. It's so easy to talk to you. It's so much fun to talk about bluefin and blue marlin. And thank you so much for letting me share some of the science. And yeah, this is a lot of fun.

Katie (01:00:30.693)
Thanks, Chloe!

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