Ep.07 Jeremy Higgs: The Science Behind Marlin Kill Tournaments with the University of Southern Mississippi

The Katie C. Sawyer Podcast

Summary

Jeremy Higgs, assistant director at the Center for Fisheries and Research Development at the University of Southern Mississippi, discusses his work in fisheries research. He talks about his background and how he fell in love with the research opportunities in the Gulf Coast. Jeremy explains his role at the Research Center and the various projects he manages, including larval shrimp studies, offshore billfish work, bull shark life history study, and oyster reef work. He also discusses the importance of oyster reefs for the ecosystem and the sport fish species that rely on them. The conversation explores the different species of fish studied in fisheries research, including swordfish, marlin, tuna, mahi, wahoo, and more. The researchers discuss the unique characteristics and behaviors of these fish, such as their feeding habits, visual adaptations, and growth rates. They also touch on the importance of studying these rare event species and the collaborative efforts between scientists and anglers. The conversation concludes with a discussion on the handling and donation of fish samples after they are brought back to the dock.

Keywords

fisheries research, Gulf Coast, larval shrimp, billfish, bull shark, oyster reef, ecosystem, fisheries research, swordfish, marlin, tuna, mahi, wahoo, feeding habits, visual adaptations, growth rates, rare event species, collaborative efforts, handling fish samples, donation

Takeaways

• The Gulf Coast offers a wealth of research opportunities in fisheries, both inshore and offshore.
• Oyster reefs play a crucial role in the ecosystem, providing habitat and food sources for sport fish species.
• Jeremy Higgs manages various research projects, including larval shrimp studies, billfish work, bull shark life history study, and oyster reef work.
• Collaboration with fishermen, scientists, and other institutions is essential in gathering data and understanding fish species.
• Sampling and analyzing fish specimens at fishing tournaments provide valuable insights into reproductive biology, age determination, and diet composition. Different species of fish, such as swordfish, marlin, tuna, mahi, and wahoo, are studied in fisheries research.
• These fish have unique characteristics and behaviors, including feeding habits, visual adaptations, and growth rates.
• Studying rare event species is important for their long-term management and conservation.
• Collaboration between scientists and anglers is crucial in gathering data and samples for research.
• After sampling, the fish are handled and donated to organizations for various purposes, such as rehabilitation and feeding birds of prey.

Chapters

00:00 Introduction and Background
02:26 Research Opportunities in the Gulf Coast
04:19 The Importance of Oyster Reefs
08:13 Managing Research Projects
15:12 Collaboration in the Scientific Community
32:12 Exploring the Diversity of Fish in Fisheries Research
34:08 Understanding the Feeding Habits and Adaptations of Pelagic Fish
37:57 The Significance of Studying Rare Event Species
41:44 Collaboration between Scientists and Anglers in Fisheries Research
56:38 Handling and Donation of Fish Samples in Fisheries Research

USM Center for Fisheries Research and Development

Transcript:

Katie (00:00.206)
What's up, you guys? Today's podcast is a special treat. Today I have Jeremy Higgs, the assistant director at the Center for Fisheries and Research Development at the University of Southern Mississippi. I met Jeremy on site at the Mississippi Gulf Coast Billfish Classic last year as he was taking all of these incredible samples from these massive blue marlin coming to the dock. Stay posted. You're not going to want to miss it.

Katie (00:33.134)
Welcome to the KDC Sawyer podcast. I'm your host Katie. And today I have the pleasure of sitting down with Jeremy Higgs. Jeremy, thank you so much for joining us. Thank you for the opportunity to be on the show today. I really appreciate it. Now, Jeremy, you're the assistant director over at the research center. How long have you been at USM? I've been with USM about 14 years. Different roles in my time here as research technician up to where I'm at now as assistant director of fisheries.

That's awesome. Where did you come from before USM? I did my undergraduate work at Southwestern College in a little town in Kansas. We had to do a summer field session at a marine lab. There was a flyer in our lobby and it was for the Gulf Coast Research Lab and it was a first SHERC class. I came down here on a fluke and absolutely fell in love, did a summer of coursework here, and then did an internship and then came back to do graduate school.

and then start working in fisheries. That's awesome. Now, did you use the word fluke as a pun or was that just... That was coincidental. Is it that... For the listener, a fluke is a flat fish. Am I right? It is. And the whale tail, the tails of marine mammals. how cool. I didn't know that. That's awesome. Well, that's all she wrote. That's really cool. So what made you fall in love with USM?

So the campus here is absolutely gorgeous. The Gulf Coast is amazing. And after being here for the summer, I realized there's a lot of research opportunities in this area, not only inshore but offshore. And the folks that we got to work with, like Jim, who's, you know, he really is a big figure here on the coast and the work he's done. So it was easy to get excited and to see passion from other people. And it really just kind of drew me into the entire environment down here.

That's so cool. I got the opportunity to visit you guys on campus last year and I was blown away by how beautiful it is there and what a special thing you guys have going on. Your whole team seems really into the process, the research and being out on the water as well as in the lab. It shows that you guys are passionate about it. We have an absolutely phenomenal team working with us in CFRD as well as other colleagues here at GCRL and along the coast. It's a truly unique place to work and

Katie (02:55.566)
a great opportunity to delve into this field. Beautiful. So Jeremy, tell me a little bit about what you do at the Research Center and some of your day -to -day life, but as well as some of your projects. So things have changed a bit over the years. I don't go in the field as much as I used to, but when I do there for fun projects, a lot of my day -to -day now is managing other programs that are going on, so different grants for the research that we are being...

that we are conducting. These range from larval shrimp studies to help inform about the opening of shrimp season every year, all the way up to larger offshore projects such as the billfish work that we do in the Gulf as well as elsewhere around the world. So currently I'm working on a bull shark project, a life history study. We also have...

some of our long -term monitoring projects that we're looking at some of the data, look at abundancies and distribution of different species. And so just a little bit of everything, even some oyster reef work from time to time. those oyster reefs, they're super important. You know, a lot of people don't realize how important they are for the ecosystem. They're a very diverse community and you wouldn't think about it on a reef, but there's so much space in between the oysters and in the sediment around that that is a

There's just a huge community that exists there that not only keeps the reef reef healthy, but also provides a lot of food sources for important sport fish. So we have a lot of small crabs and shrimp that are on the reef that the trout and red drum love to munch on. So like it's a really, really important community. How does that end up affecting the sport? Like the offshore is that does that affect the offshore fishery at all? Not not so much. Our reefs are pretty inshore.

As the salinity increases, you lose the viability of the oysters once you get too far south of the islands here. All of our reefs are inside the Mississippi Sound, so it's really just for inshore sport fish species, I would say it's the most benefit out of it. That's cool. Oysters also serve a huge purpose in terms of filtering the water, keeping the water pH levels.

Katie (05:18.221)
as they should be? Absolutely. Oyster reefs are wonderful filters of a natural environment. So a healthy reef has a lot of good water quality around it. Even though in our area, everything is very murky, so you would never tell, but when the reefs are very viable, they're continuously filtering. That's how they feed. And so they pull a lot of the nutrients and sediments back out of the water. Now, I love that you said that the water is so murky there, because I learned something in your lab last year that just kind of blew my mind and also made so much sense.

Now I'm from a small town on the Texas Gulf Coast and we have an incredible inshore fishery as well. I'm not a very good inshore fisherman, but I do like to do it in my pastime and in my free time. And what I learned about was the size of the ear bones. Now we're going to get into otoliths a little bit later, but the size of the ear bones, which are otoliths, of the red drum and why with that murky water. Do you want to share that a little bit? Yeah. So.

The ear bones in fish or the otoliths help with a lot of different things. Fish can listen for sounds to hunt or whatever it may be. If you're in murky water, you have to rely on your hearing a lot more than your visual senses. Your ear bones generally get larger in that case so you can have better sound reception as well as if it's a species that makes noise. The drums...

with their name, they drum, and so it helps up with that sound perception. And then if... That's so cool. Yeah. If you move offshore where it's clear, beautiful water and even a huge fish, they like a marlin, the otoliths are very tiny, microscopic almost, because they don't need them. They're visual hunters, so they don't need that sense as much. That is so fascinating to me. But they all have them. They all have these ear bones. They all have these otoliths. And...

We're going to get into that a little bit later, but I just love that. I just love that drum, that drum tidbit fact. I was like, wow, well, that makes perfect sense. You know, that's how they're hunting. That's how they're finding their their prey and their food and their nutrients, because the water, I mean, here in shore, you're just going to get murky water. It's brackish water. Sometimes it's super clear, but it's cool when you see the differentiation between fish and fisheries around the world and how they feed differently and how they've evolved differently to support that.

Katie (07:45.453)
that zone that they live in, right? So I met you because I was fascinated about the work that USM is doing with the fishing tournaments. Now, Jim and I talked a little bit last week about the culture and the history surrounding the Gulf of Mexico fishing tournaments and the science that's come out of a very important collaboration between fishermen and scientists.

And I think it's a very important space. It's a very important thing to share. There's information that we wouldn't be able to derive if there was not that collaboration. And we can't protect a species correctly and manage a species correctly without first understanding them. So we're going to go ahead and jump into your work at the Mississippi Gulf Coast Billfish Classic in Biloxi. And, yeah, go ahead and just take the wheel. Tell us a little bit about, take the wheel. Let's go. All right.

So I will have to start out and say that my introduction to the Bill Fish Classic over in Biloxi was probably one of the other reasons that I am here today, because what's more exciting than that, going to see giant fish as an undergraduate student. So it sucks you right on into the whole environment, and some of the biggest fish I'd ever seen came in at that tournament. And so I've been working with our group at the tournament since probably 2011.

missed a few years here and there, but we have a great setup on the dock. Bobby, who runs the tournament, has been very, very good to work with over the years, and we always have a nice tent set up just off from the way scale. The dock crew, Bert and his crew, and Bert and Jack and everybody, they know what we're looking for and the samples we're looking for, and they're super great to work with. And so we're a little bit off from the main stage.

But as soon as the fish is brought in, you know, hold off the boat as we've seen time and time before and weighed and measurements taken, a bunch of photos taken, because these are amazing fish that are coming in, they get brought over to our tent. And we usually have a team anywhere from five to 10 individuals of researchers that work with us and students that are here for the summer and some other volunteers that we get. And once the fish is brought over,

Katie (10:06.989)
We bring it onto some of our tables. We do full measurements. So what we're looking for is, especially with the billfish, we're looking at lower jaw fork length. That's kind of the standard measurement for length and everything so that we can then correlate our work with other studies that have occurred elsewhere. And then what we typically are doing is opportunistic sampling for reproductive biology and then hard structures for aging. So we talked about the otus a little bit, and in marlin, again, they're very, very tiny.

So a lot of times the anal spine, the second anal spine is used because it's also a calcified structure. So then we can retain that. And since we have the individual, we also make sure we get a muscle plug for stable isotope analysis and then to pass along to ourselves or other colleagues as well as removing stomach contents to see what they've been feeding on, if we can get any insights into their diet. Besides...

bait that was used in the tournament, which usually is pretty easy to identify that it was bait and not a natural prey item. So that's, I'm going to stop you for just a second because I mean that's so inclusive and that's all information you wouldn't be able to get from a fish that's released back into the ocean to swim another day. Now obviously with these marlin species I'm passionate about blue marlin, I absolutely love to see them swim away healthy, but when they're being brought back to the dock it's

Absolutely incredible that you guys are being able to take all these samples on these fish So you're taking the length and you've got the weight so that you can as you said correlate it with previous research and see if you can find a good common ground as well as now I'm gonna have you just talk a little bit about otoliths and Why you use the second anal spine? You mentioned calcium. Let's hear why like the differentiation we already talked about the differentiation between like the drum otolith and the marlin otolith and why I

And with the drum otolith, you can use that to age the fish correctly. I mean, is that correct? Correct. Yep. Okay. So, and how does that work? You, you put a dye on it and you put it under a microscope and it shows rings like in a tree, for example. Just like, just like you'd see in a tree. so depending on the species and how large the otoliths are, you have to section them on a, a low speed saw. And so what that does is it creates a nice little.

Katie (12:32.781)
a nice little thin slice that we can then mount on a microscope slide. And then when you put them on the microscope and the light transmits, you can see those different rings or the different rings that are banding up.

Knowing some prior life history about that species, you can say, okay, these are generally spawned this time of the year. These seven rings plus this amount that's on the end that hasn't formed in the next ring gives it an age of seven and a half or whatever the number may be. That works great on any hard structure that's calcified. Well, not any, but probably most. In many fish species, it's easiest to do that with their otoliths because they're easy to obtain.

and they're large enough that they're easy to use. Well, in any of the pelagic, most of the pelagic fishes, their odilus are much, much smaller. And in some, like swordfish and marlin, like they are, they're so, so tiny. You can almost barely even see them without a microscope when they're complete. And so you - They're smaller. They're like smaller than half a grain of rice. You showed me last year, you pulled some out and we looked at them and they're in this like membranous layer.

Correct. There's two on each side of the fish. Correct? There's three on each side of the fish. Or is it four? There's three on each side of the fish. That was close, right? There's three on each side and the largest is the saggula otolith. That's what's used most often because it is the largest. So it's easiest to work with. The other ones are half again as large as the saggula or even a third again, you know, as large. So they're much, much smaller.

They're crazy small. Crazy small. And especially, you know, half a grain of rice might be generous with some of them. So they're very easy to miss. They're very hard to get out. And so other studies have shown that you can use the anal spine as a good alternative aging method. So it's also calcified structure. It's going to increase in diameter over the entire life of the fish, just like the otoliths increase in size. So those bands are laid down the same way.

Katie (14:45.837)
So it's a good proxy to use and it's very easy to get from a fish that has come into a tournament. And so section the same way, put down on a microscope slide, just a much bigger version of what we need to look at so we can kind of get a better age for them. That's so cool. Now let's talk about like the reproduction studies. So especially because now we understand how you're aging the fish.

How do you look at their organs to decide, to figure out, to decipher what's been going on in their life? So, depending on the species, but most species do not have any kind of sexual dimorphism. So that means you can't tell the different sexes apart externally or visually, for fish. Sharks are totally different. So, internal examination is necessary. So if we, and that's why these...

tournaments are so important for these big rare event species because we don't have a means to go and collect these fish and we probably wouldn't because of what they are. But since they're opportunistically being brought in, let's get as much information from them as possible. So this then gives us our insight into looking at the reproductive biology of billfishes and tunas and such. And so internal examination, the gonads are removed, it's determined if it's either female or male. And then we have a team member.

that works with us that is very good at reproductive histology. And so what that is, is they take a sample of that gonadal tissue and it gets stained and processed and very, very thinly sliced. And they can actually look and see at what phase of the reproductive cycle the animal's in. And if it is during the spawning season or if it's going to be spawning capable or, you know, those kind of things. So we can really kind of.

you in on the what portion of their reproductive biology is occurring and their seasonality is occurring. So what are the phases? Is it like a cycle of the year or is it throughout their lifetime? So it's cycle, I don't want to say cycle of the year because some species are not annual paradises so they don't reproduce every year, maybe every other year and maybe multiple times a year. Some fish are batch spawners so they can spawn numerous times over a period of

Katie (17:03.565)
or three or more months. And I'm not going to lie to you, I'm not a fish reproductive person. I know about that much. Me neither. You know more than I do. I know about that much. And so every time I talk about it, I'm like, hey, Anna, come here, tell me a little bit more about this. Anna's awesome. But for the marlin, we're looking at a yearly cycle. And so, well, for the listener out there, these fish that are brought into the Biloxi tournament have to be a certain size.

They have to be a certain length legally to be harvested in the United States. And these tournaments have that length even longer for them to be brought back to the dock. So most of these fish are a big size. They're over 500 pounds generally. And Jeremy, do you want to talk about the female and male, what we know on blue marlin specifically? So the larger fish that are brought in the tournament,

are more often than not females. The females in most fish species grow to a larger size than the males do, and that's for reproductive purposes. The larger female can reproduce more offspring, because they have more viability and more energetics built up in the system to do so. So a lot of the fish that we see at the tournaments that come in are large females, which in the scheme of reproductive biology is way more important to know about than the males.

The males don't, they're there, they do their thing, they don't do anything else. The females are what we can use to gauge. Well, we can use to gauge like fecundity. So how many offspring might be expected? So they're much more important. And so these tournaments, we have the opportunity to collect those kinds of samples. So we can look at, you know, how many eggs are being produced over that season. And not all of those are going to be viable, of course. And that's.

their way that their reproductive strategy is millions of eggs at a time and a very small number of offspring that survived that. Whereas some other species may only produce two or three offspring, but they're expected to survive because they nurture them to a larger size before, you know, their live birth occurs in some species. Right. Definitely not in Markle though. No, absolutely not. Only a handful of fishes and they're very little fishes.

Katie (19:29.357)
That's so cool. That is so fascinating. I actually didn't realize that there were fish that do live birth. So I think some of them are down in your guys' neck of the woods, in some of the rivers down there. So they're called live bears, and they're very just little small, small guys.

How interesting. Okay, that's a story for another time. You kind of blew my mind there. I had no idea. But okay, yeah. So yeah, no, Marlin, don't lay their eggs and then watch them grow and care for their offspring. It's far, it's actually, and you guys have done some interesting studies on juvenile billfish too, correct? So Jim has done a lot of studies on the blue current and sargassum and collection of larval black

pelagic species while they're out there doing that as well. And so... That's awesome. We have a fairly good understanding of some of the early life history of billfishes in the Gulf of Mexico. And so he's collected some teeny tiny little fellas and collected some eggs, kind of an idea of where spawning might be occurring. And even with the little larvae, you can backtrack with oceanide models to see where they may have been spawned from.

So you can kind of go back in time and potentially see where that event may have occurred. So, Jeremy, what I want to understand and I think what I do understand based on an article I read once is that you can tell based on what the gonad tissue is saying that how much that fish has spawned, like how long it has been of spawning age.

Can you get an analysis of that or are you just getting an approximation of how many eggs more or less are being released? That is a good question and I don't know the answer to. That's fine. Okay. But you have somebody that's working in that field. We'll just have to have that conversation for another time. And that's why you're collecting that, those samples at the tournament so that we can understand more about the reproduction of these fish.

Katie (21:41.261)
how often and how much along correlated with their weight and their age correct? Yep. And so with the, so what are you, go ahead. Yeah, no, go, no, please. so with, what we do collect for the reproductive biology, it can give us kind of a size or age at maturity. So by looking at the dermatal tissue, you can tell it what, if it has reached maturity or not, which is one of the big things that we, we use, cause you can look at it and macroscopically, so to the,

to the naked eye, you might have a good guess, but microscopically it might be different. So that's where that histology comes into play where they do the very thin sections and then they can actually, our team that does the reproductive analysis can look at the different sizes and structures in either sex gonads. And so they can tell where they're at and it's much more, it can be much more accurate than just a visual examination of it. So. That's incredible.

So cool. So what about the muscle plug? Tell me about that. So, stabilized soap analysis can kind of give you an idea of trophic level, which we would expect in a marlin or a tuna or any other large predatory fish to be very high on the food chain. But it can kind of give you an idea of where they fall in line with other species. And looking at different elements,

from analysis of a muscle plug, you can kind of actually get an idea of how much, if they have an inshore signature or an offshore signature, so they have any ties to any specific region near shore. And it depends on the elements you're looking at, depends on the questions you're asking. So there are some pretty neat studies you can do with just a muscle plug. That's been stored correctly and all the fancy stuff afterwards. We...

We often hand those off to colleagues. That's not something we are set up to do here in CFRD, but we have colleagues over on our other campus here in USM that looks into that. So not only are you collecting these data for yourself and your studies, but you're also collecting these samples for other scientists elsewhere. I mean, USM, but I, when I was there with you last year,

Katie (24:01.869)
You had other institutions there. You have collaborations with other universities. Absolutely. The Bill Fish scientific community is not very large. I don't know how many of us exist, but there's enough. But every opportunity to sample and everybody has a different interest in what they're looking for. So over this last summer, we had some colleagues from University of North Florida that joined us. We had some.

federal fisheries partners that came and were collecting different samples that they were looking at for federal management as well. And a lot of what their samples are aligned with what we take as well. So we work back and forth. We've sent samples up to the Northeast. We have colleagues over in Texas and some over on the West Coast. So there's always different opportunities to collaborate and whether it's academic with NGOs. So we work with the Bill Fish Foundation on a lot of projects as well.

We work with IGFA on some projects. We have some industry partners either directly tied to the billfish industry or just the overall outdoor sportsmen professions. And so industry partners don't often have a specific research question they want. They just want to be able to provide help to make sure we can get the research that we're interested in. And so that's...

super wonderful. And then the tournaments that we work with. They're a huge component to this. And whoever the laymaster is at the tournament, depending on which tournament it is, they got to know us over the years a lot because Jim has been doing so much work with the tournaments for so long. And it's been such a large part of his career. So they're excited when we come. They're excited when we have the opportunity that we can come over to one of their events and opportunistic example. And then...

probably the most important collaboration we have is with the actual community. So we have this great community of fishers, whether it's billfish or inshore fisheries, and after you've worked with them and you've communicated with them enough, they're excited and they want you to sample their fish. And if you don't, they're like, why aren't you sampling my fish? You sampled Bob's fish, you better look at my fish.

Katie (26:25.773)
So there's no shortage of samples when we have the opportunity. That's awesome. I love it. Do you know, I remember she told me a little bit about it, but the professor from Florida last year that was over at the tournament was taking samples from the base of the Marlin bill. Do you know anything about her studies? I don't. I haven't. What she was doing. I haven't followed up with her recently, but I know what she's looking at is.

She was looking at the structure of the bill. We sent her a number of bills several years ago, and so she was doing that for her dissertation. Now she has a whole slew of students underneath her doing even more research. I don't exactly know what they were doing, but it was only a thin section of bill they were interested in. First off, I just got chicken skin because...

You said that you guys have been working with her a little bit over the years. She's looking at the bill and she did that for a dissertation and now she has a slew of students working under her. So what I get from that is that she was studying the Marlin bill, a whole bunch of questions came up and now there's a bunch of, a bunch of people doing research on this so that we can understand this fish better. I think that's incredible. Again, chicken skin. She was telling me there was something about,

the gelatinous membrane at the base of the marlin bill because these fish, we've already established they're visual feeders and they use this bill on their nose to strike the bait, stun the bait and then eat the bait. Right? So they, they use the bill to hit the bait, whether it be a two pound mackerel or a 15 pound tuna and then they consume it.

Right. And so that can be a pretty, that's like a pretty, can be a pretty big shock, of the, the bill hitting the fish and they do it very strong, especially these big blue Marlin, especially when these girls are hungry and, we don't, I was angry Marlin, they don't mess around, but, and so what she was studying was the ability for that shock absorption to, and,

Katie (28:47.917)
what she can correlate from the bill strike into our thermodynamic world today. So I thought that was very fascinating. I don't know anything about it. It was completely over my head, but that's why she was just, she was taking that like small sliver at the base of the bill and she just started telling me all about it. I was like, wow, you're interesting and this is super cool. And I had never even considered that. So what about the samples from the stomach?

You talked a little bit about that most of the time it's just bait, but what else are we seeing there? So a lot of times in the marlin that we've examined it's been bait. We do occasionally see some mahi, a couple of small blackfin, but one of those, and a little bit off of marlin, we'll jump over to swordfish. We had the opportunity to sample quite a large number of swordfish from the Biloxi tournament a few years ago.

And if you know anything about swordfish, you would assume that they're eating squid. That's what everybody says. And that is not what we found. We found squid, but that's not what we found as their primary diet here in the northern Gulf of Mexico, or at least from those tournament samples. We found what's called a luminous hake. It's a little silvery fish that lives on the bottom. And they absolutely love them. And there were hundreds of them.

in the diets. And then on a completely flip side of that, we'd find a lot of blue runners, which, my gosh. I mean, who are surf, who are at the surface. And you know, swordfish feed at the bottom and they come to the surface at night and feed them. But it was such, those two items were the most important items in their diet. by far more than any squid or invertebrate that we saw. How interesting. Now I don't,

I don't really know anything about swordfish. I'd love to get some swordfish specialists on here. I've never actually caught a swordfish myself, but this idea that they feed both at the base bottom of the ocean on these little silvery fish and you call them hake. They're a luminous hake. Tell me again. Luminous hake. What a cool name. What a cool name.

Katie (31:14.477)
Sorry, got distracted. So, that they're feeding on these like obviously deep water fish and then the blue runners at the surface already that going through the water column like that is Exceptional. it makes me wonder if there are do you know if swordfish are negatively buoyant like tuna? Or do they have a swim bladder that The chain that that equalizes them. It's okay. I don't know I don't know if I've

Billfish are negatively buoyant. I've never been able to find that information. I just know that tuna are, you know, obviously there's a lot more science out there on tuna because those fish can be, there have been economic values put on those fish. So there's more money put into the studies so that there's more studies being conducted. But the fact that you guys are doing this with the tournament show how much the recreational angler,

fishery has to do with the studies and also how much money is put into these tournaments and brought into these communities of these various tournaments all over the world. really puts a lot of value to these fish, but okay. So these swordfish are eating these very different species. Now Marlin are surface feeders. We know that right. And swordfish go surface at night and bottom in the daytime.

And the so it's really, really dark down there. Like even if it's daylight, you guys like the water, it gets dark deep down there. How deep are they feeding? Jeremy, do you know? So a lot of the anglers that we talked to at the tournament are fishing and from colleagues down in Venice that are doing charter trips and personal fishing, a lot of these folks are dropping between 1500 and 1800 feet.

and they're hooking up on the bottom. And I can't imagine fighting a fish up that long, but they love doing it. So I mean, they are, that is the very bottom of the, of the areas that they're in for the most part of where folks are fishing. I mean, I'm sorry, they can go, swordfish can go into deeper water and I'm sure they're feeding even deeper, but nobody's fishing that far out or that deep out and hooking up really past 2000 feet, at least here in the Gulf of Mexico. So,

Katie (33:40.205)
With these fish feeding so deep, they've got to have a lot of differentiation in their eyes than the, for example, the Marlin do. Is that true? Do you know anything about that? Well, their eyeballs are absolutely huge. I mean, Marlin have really, you know, large eyes. And then I would say most of the swordfish eyes that we've seen are probably half again as large, if not more. That's one.

Wow. Yeah, really. Do you have a photo? Do you have anywhere like a photo of two side by side or like even like two we could with measurements that we could show on the video? I probably do somewhere. We should find that because that is fascinating. So explain why the swordfish eye would be so much bigger. So that well, because they are deeper down and their otoliths are still tiny. So there's still a visual predator. So they're picking up as much light as possible.

from what little light levels there may be or may not be at that point. That's insane. Now, the hake is luminescent. I don't actually know if it lights up or not or if that's just its name. Okay. I know that a lot of creatures down there have some bioluminescence in them, like squid. Squid have bioluminescence. So...

I've never been down there personally. I have no desire to go down that deep, but what we know, I follow an account on Instagram. I need to figure out what I need to, I don't want to lie to you guys, but essentially it's like deep water and it's scientists that go, they have their little rover style thing that goes deep into the ocean and it's fun because they drive this rover around, they'll find something and it's a group of like four people just talking over what they're seeing and it's pretty geeky and it's pretty awesome. It's a great.

It's a great channel. I should get them on. But so what we know based on studies like the ones you guys are conducting is that swordfish are visual feeders because one, their otoliths are tiny and two, their eyeballs are huge. Yeah. And they're feeding in the entire water column. So it would be a disservice to them to, you know, not be visual when they're up in the open ocean, which they often are at night.

Katie (36:04.653)
I mean, they are during the day too. You do see them sunbathing from time to time, from what I've been told anyways, I haven't seen them, but there's plenty of anglers that have come across them at the surface or near the surface during the day too. So they're really living in both environments and they've adapted in a way that is just phenomenal to make that happen. That's really interesting because there's really not a lot of pelagic fish or fish at all that can do that. Like,

I know that tuna, especially bluefin, the master of the tuna, are going throughout the water column pretty regularly. And I know they're feeding both at the surface and down deep, but it's a pretty spectacular situation to find in the fish species. absolutely. Yeah, there is not very many representative species like that. So it's a truly unique situation. Cool. So.

What do we know? Do you guys do any studies from the Marlin eyeballs? We have not done anything with them to my knowledge. One of the things that we've been looking into is seeing if you can pull some stabilized tubes from the different layers of the lenses, maybe if you can age the lenses because they should also have a similar structure to some of the other features. And so we have not done...

into that real deep, but I know there are other groups that are looking into that. They're looking into it. Another pun. Can you tell us a little bit more? I know you told us about the muscle plug already, but you were talking about stable isotope data and the trophic levels. Can you just clear that up a little bit more layman's term for us? Yeah. Simply put the food web.

So you can look and see, depending on what element you may be looking at, or if you're looking at a whole suite of species, you can see where they fall out in the food web. So are they primary producers? Are they primary consumers, secondary consumers? Or are they apex predators? And so depending on what your question is and what organism you're looking at, you can kind of build this web and see.

Katie (38:26.957)
what their food web world is per se. And one of the things we're doing with that colleague of mine down the hall is a parasitologist. And so he's, you know, he likes looking at the, he's been looking at the parasites of some of these billfish. And realistically, their entire world is inside this billfish or another small fish that this billfish ate. So he can look at,

where their trophic level is and see how they fall in line compared to either the diet items that are in the marlin's stomach, or is it actually feeding on the marlin? So is it a higher trophic level in the marlin? So could that be an apex predator per se because of how it falls out based on different isotope signatures that you're looking at? So it's really an...

It's really a neat, like crazy world, depending on what your question is. Right. So, I mean, there's so much we think we know, but when you not until you get a deep, deep look at it, can you really have the answers? I remember I remember that the research assistant that was gathering the parasites at these from the Marlin last year at the tournament, and she was just like running or.

burning your hands all over, all these little like creases in the fish and just like, I mean, to be fair, when I am, for example, rigging a ballyhoo and it has, ballyhoo often have a parasite in their mouth that essentially just takes over their tongue. I mean, I don't know, I don't get too into it, but when I see that parasite in the ballyhoo's mouth, it gives me the, the Higa Jibis. Like I do not like that. I do not like that. And I was just like,

I don't know, my jaw was kind of dropped. My eyes were bulging a little bit watching her just cover through this marlin looking all up in the gill plate, all up in the, the cradle fin and with her tweezer. And she's like, I found one. And then she's like tweezing it off and sticking them in, in the tube. And I mean, these people that are collecting the, the, this samples for these studies, they are getting dirty. You guys, I need to paint this picture a little bit and we'll, we'll show some supporting documentation.

Katie (40:48.653)
but it's not a pretty job. Like they, you guys are getting so nitty gritty down in there. I've personally never seen fishermen get that far into like, you know, this is the life, this is what we're doing and we're going to do it and we're going to make a difference with it. And I think that is so cool. Your whole crew is so cool. And I'm very, very thankful to have every one of them. And I think we do that super

deep dive in because it's such a rare event for us to have an opportunity to collect these samples. And so while we have that chance, let's make sure we get absolutely everything we think we may want. And then usually some more that we don't, we may or may not ever get around to doing anything useful with it or find out that, well, we don't need to collect that anymore. We know better now. But we know better. Well, we know time -wise better. well, that didn't do it. Yeah. So.

It's better more than not enough. Absolutely. So what other, so we're talking about your Marlin sampling, but it's not just a blue Marlin tournament. You're also seeing other species of fish. You want to tell us a little bit about that? So depending on the tournament, we, we may have swordfish that get brought in and that's just, it's a new budding fisher and not really budding anymore. It's a new ish fishery here in the Northern Gulf of Mexico. And so we're starting to see a lot more.

And so it's a great opportunity to get a lot of samples. So we've been really jumping on those opportunities when we can. The yellowfin tuna fishery has been booming here for decades. And so a lot of the billfish tournaments have a yellowfin category. Usually by the time the Biloxi tournament rolls around, the bluefin fishery is closed down for the year in the Gulf of Mexico. But we have had one bluefin come in over the years. And...

Jim got to sample that fish, of course. If it's ever open and it works out, we're happy, happy to collect bluefin samples because they are very few and far between in our area anyways. Especially in the Gulf of Mexico. We had Chloe on previously this year. She's a PhD candidate over at Marine Hopkins studying getting her PhD. Sorry.

Katie (43:10.605)
She's studying bluefin tuna and she's amazing and she gave us all sorts of details. So we know that these bluefin, there's a population of bluefin that are spawning in the Gulf of Mexico. And that's generally, like you said, you guys are a little late, but it's generally March, April time. And being able to sample these fish is so important based on all of the information that you've already presented us with, Jeremy, just to be able to have that.

data on fish that are caught is so important for the long -term management of these species. So it's cool that you guys have gotten to do that a little bit as well. yeah. And so, and to add onto that, because the recreational quota is so low in the Gulf of Mexico, it's by weight. So every year the number changes, but we're talking maybe two or three fish total for the entire Gulf of Mexico. When one's caught, phone calls are starting to be made. And it's like, who wants...

who needs this, who can get close to this fish and get samples from it. So the community knows how important it is as well. So I'm sure she loves that for her dissertation work and the ability. And I'm sure Jim has probably sent her plenty of stuff he has in freezers over the years. I'm sure he has too. Yeah. Yeah. She works with Dr. Barb Block. yeah. I'm sure he has. Yeah. Okay. So we've got yellowfin, swordfish, marlin, tuna.

We don't usually get any blackfin tuna that come into the tournament. Every now and then there'll be one that shows up that we have an opportunity to look at, which I think is a pretty interesting species that we need to start looking at more. I'd like to start looking at more. It's an underappreciated tuna is the way I feel about them. I can second that one because I have no desire for blackfin tuna.

I think it is probably underappreciated. Tell me a little bit more why. I think they're delicious, but in our side, in the scientific side of things, we know very, very little about them. There's so many of them, nobody's really taking the time, much time anyways, to look into them and their different parts of their ranges. Some work's been done off of Florida.

Katie (45:33.293)
off the East coast and the Florida Straits, but really in the Gulf of Mexico, there hasn't been much work done at all. And it's just, I think they're just overlooked in that sense because there are so many of them at the moment. Didn't you say that you're seeing a lot of them in the bellies of the fish we're catching? We do. So we do see them as a, as a prey item in a lot of the larger, pelagics and a lot of the sharks too. So. Well, all the more reason that we should understand them better if they're such an important food source for these larger fish.

Absolutely. I mean, you see huge balls of them when you're offshore. So there's always something good to hanging out with them. Okay. And then also what else do you have outside the tuna species? So we collect mahi samples when they're brought in. Mahi are interested in the fact they don't live very long. They're very short lived species. They're sexually mature by six months or so and their entire lifespan is only about

four -ish years. So they're very, they're boom and bust. So. And they, aren't they like the fastest growing fish in the sea as far as we know? I would bet they're close if they're not. I mean, cause you have nothing, I guess some things do, but almost nothing matures within just a couple of months of, you know, being a larval fish to reproducing in less than a year. So that's insane. And the fact that they only get to be about four years of age, I mean, we've all seen those like hundred.

town mahi photos over in the Pacific. Like they get huge over there. I've personally caught like really big ones when we were fishing out of Costa Rica. This last year, we were fishing the Baja bite over in California, I'm sorry, Baja California in Mexico. And, we were fishing the striped Marlin season and the mahi there have just been, as you know, it's an El Nino year this last year.

And I think because of the increased water temperatures, we just had a big just boom of these mahi all throughout the central Pacific. And they were so there were so many of them when I know that I was getting reports from Ronnie Fields on the mamacita saying that in September they were everywhere. By the time we got there in late October.

Katie (47:51.853)
they were just, we couldn't even pull baits. We were just pulling teasers because we couldn't get a bait to a striped marlin without a mahi snaking it. And then as the season progressed, come like late December, these fish have like quadrupled in size. So now when you get snaked by a mahi, they're still just as fast. And when you get snaked by a mahi, now you have like a big fish to reel in and you're like, dang it. Like these guys can't leave us alone.

They're also one of the fastest fish. I mean, sailfish are super, super fast, but mahi are also extremely fast. Do you guys do any, do you know anything about that? Like what are your studies? I mean, I know that that's probably information that you would be better derived through satellite tagging is their speed and that sort of thing. It would be, it'd be better. That would probably be the easiest way to actually get the data back. And I don't know if anybody's, we have not tagged any mahi here.

They're doing that in Florida. I know that Chloe personally did that over at CMAP. I think, I don't want to lie, but I know that she started off satellite tagging Mahi and learned a lot about him. There's a lot of work being done with them for sure. But yeah, like you said, I mean, they grow so fast and the fact that they reach sexual maturity at six months of age is insane. Yeah, absolutely nuts. And so...

But with the satellite tag, and we do do that on other species, so we can kind of calculate speed based on reports that we get back in as long as we get good data back. That's important. That's so cool. And so with those mahi samples, you are able to like, like we talked about the the maturity of reproduction. Do you know how often they reproduce once they reach that maturity? I actually do not.

because I haven't done much with the mahi samples. We collected them and I passed them off and I don't actually know what they've done with them since then. But that's cool. I mean, the important part of this conversation is the fact that there are all these questions and because of the samples you guys are taking, we have the ability to get the answers. And I think I find that absolutely amazing. So we have mahi and then there's I think there's one more. We have been collecting wahoo.

Katie (50:13.037)
as we're able to. And they're a little bit... God, I love Wahoo. They're a little bit trickier to... I mean, the normal workups are the normal workups, but like age and growth of Wahoo has been a challenge. Their otoliths are very tough to age, which may sound funny, because you'd say, they're just rings. You should be easily count them, but they're not always just rings. There might be some...

some, I don't know, distortion, I guess, would be the way to put it. So it may not be just a clear ring that you can see. It might be that there's broken bands or there's things are just, they don't quite look right. So, you know, Jim's, Jim and, that's interesting. Specific to wahoo. And there we have, we see that with other species as well. The wahoo of their tournament sampled fish have been the problem child for that by far. That is so odd. Now, do they, I guess they don't have a second spinal fin?

What did you call the gap? So I don't know if anybody's tried to use an anal spine or any spine off a wahoo. That would be something to look into actually. I don't know if anybody's tried that or if it was something that we could even do and if there's enough there. I mean, plausibly any calcified structure like that should work. That's so interesting.

How fascinating that all of these pelagic fish, now are all of these fish that we've talked about considered rare event species? I wouldn't say that the tunas are rare events. Bluefin's definitely are, but the yellowfin fishery is booming. And when the mahi are in, the mahi are everywhere. Yeah. There's nothing rare about the mahi. I'm just kidding.

I have a little bit of like anger towards the Mahi now. It's a little residual, just PTSD on the Mahi scene. But yeah, okay. So the bluefin swordfish. I would say that the technique has been largely figured out for swordfish like it has for yellowfin. And so they are less of a rare event species now than what, at least in our area, than what they were even a decade ago.

Katie (52:30.349)
I know when I started working on some of the swordfish projects we had, I was looking at landings data and everything around here comes out of Venice, Louisiana for these large fish because it's so easy to get offshore from there. And so I was looking at Louisiana landings data and of those reported and I'm assuming most of them were reported how they're supposed to be, there was only like 14 landings for the state. Within three or four years, we were well over a couple hundred landings.

And so, and I know it's grown and built since then. I haven't asked for the most recent data in a few years. But you can go down to Venice, you see swordfish on the dock all the time. And the folks that are fishing for them, they've got it tuned in. A good buddy of mine, Peace Marvel, who's down there, he has, I think the last time I talked to him, he's got something like 900 under his belt that he's caught on his boat in the last few years.

And that's insane. It's just, it is wild. So I would say they're becoming less of a rare event now that more people are entering that fishery. But blue marlin are definitely a rare event species. Yeah, they're out there. We see them in the tournaments. So when folks are fishing for them, you know, Biloxi tournament last year had an insane number of releases. I can't remember. I can't remember exactly what it was, but it was, I feel like it was around a hundred, if not better. Like it was a lot of releases last year.

But that doesn't happen very often. There's only a handful of tournaments. There's only a handful of folks that are fishing them on a consistent basis. So outside of those big events, there may not be very many of them that are hooked up and landed. So they are definitely a rare event. White Marlin, I would say, are a rare event here. I only know a couple of charter boats that have hooked into them. A few of the tournament boats that I know that I've talked to have hooked into them. But...

We never see them. We never see them on the dock. I don't really know about sailfish. I know there's, I mean, we have the sailfish runs, but I don't know how heavy those are targeted and how many are really caught, caught, released or even caught and landed. I'm just not sure about those ones. It seems like the sailfish fishery in the Gulf of Mexico is more prevalent in the Southern part of the Gulf, like off of my shore. We have in...

Katie (54:58.797)
Generally in August and September, I could be wrong because I say it's my shore, but most of my fishing experience has been done elsewhere outside the Gulf of Mexico. But we do have some really great tournaments like the Billfish Pechanga out of Port Aransas, Texas that targets light tackle species like white marlin and sailfish.

and we have a really good fisheries sometimes in those months for sailfish about 60 miles offshore. Now 60 miles from here is very close. Yeah. yeah. Our fishery is far. So but but yeah, in the southern Gulf, you have some good light tackle fishing tournaments. Definitely. That's interesting. So I just think it's great that.

the scientists have, and you know, led by Dr. Jim Franks, he's really done an amazing job. And also the Billfish Foundation for putting people in touch with each other, which is really cool, but just have figured out to collaborate with people that have devoted their entire lives to chasing these rare event species. Like we do it, we do it because we love it. We do it because we love being on the ocean, but also the fact that we can help contribute to protecting them is essential.

So I think that's really awesome and I really appreciate your work with that. Before we close up, I have a couple of questions for you. I do want to touch on the fish themselves when you guys are done taking samples. What happens with the fish that are brought back to the dock? Let's talk about the marlin specifically. Because, and I want to say to the listeners, we have blue marlin is not the best fish to eat. It's good. Every now and then, I think two times in my career, we've

unfortunately pulled up a dead fish either from being tail wrapped or having somebody that didn't know what they were doing driving the boat, unfortunately. And in those two times, we ate the fish. Now, I find that the best way to consume blue marlin is by smoking it and then creating dips and smoked. Smoked blue marlin is pretty good, like on a bagel or whatever it might be.

Katie (57:02.893)
but all in all, not the best fish to eat. Whereas you have different species of billfish that are better. For example, spearfish is extremely delicious. But with the blue marlin, they've been brought back to the dock. They're not cleaned offshore because their weight is what qualifies them for the tournament. And so they want these fish to be full size, full weight, all the way on the scales. And then you guys take the samples from them.

So that fish has gotten mussels taken out. I mean, it's long dead. Mussels taken out, eyeballs taken out, bills cut off. Sometimes people want to keep the bill for art or a trophy to remember the fish and the situation and their time on the water with their team. The anal fins then cut. There's a lot of samples that have been taken. So what happens with that fish afterwards? So it depends on the tournament, but I believe every...

most every if not all are donating that meat to a cause after the tournament for the marlin. Tuna, swordfishes, mahi, a lot of that goes back to the boat if the anglers would like it so that always goes back. Although we do get a lot of fish that are donated to the Blutzee tournament as well so we'll have donated tunas in the ice truck that...

that go to good causes. And it just depends on the tournament and it depends really year to year where that donation goes. So it may be to shelters, it may be to other good causes, but the meat does not go to waste. It is provided to groups or folks that may be in need. May be able to use it. So.

You touched on a couple of things. First off, that it's given back to the tournament on some of the meat like the mahi and the tuna. And I know that they actually, I'm pretty sure they prepare it for the like the final party night. They'll have like a fish fry or something and feed everybody. Now for the marlin specifically, I have some insight on that, but you touched on the ice truck. Can you tell us a little bit about that? So the one we're using right now is pretty fancy.

Katie (59:21.005)
Compared to ones we've had in the past. Travis is a really nice setup going on. And it's just a large trailer that he converted over and he packed it full of, I'm assuming it's blown in ice. And so these fish, as soon as we're done sampling them, they haul it off and they are packed down and they are well preserved and kept in as good quality. Well, I see, I love that. Jeremy's very polite about it, but I've seen Jeremy's team.

haul a 600 pound marlin over to the ice truck, take a saw, cut it up in like concise pieces, lay it nicely in the ice truck. They're covered in the gore, but the fish looks great. And what Travis was telling me last year, actually he found a couple organizations. It's not so much the food banks with these blue marlin as it is with rehabilitation keeps. So he's found a couple organizations that are rehabilitating.

birds, specifically sea birds in the Gulf Coast, all over the Gulf Coast. These birds are getting brought in and they're birds of prey. So their natural food source is seafood. It's fish. That is what they're supposed to be eating. But it's very, very difficult for the rehabilitation keep to be finding fish to feed these birds because that's so expensive. That's so expensive. So Travis,

has figured this out and he's actually bringing all these marlin to feed these birds throughout the year. That is great. So that is, I did not know that he had started doing that. That is also a wonderful way to disseminate that, you know, the marlin that are brought in. And that's really, that's really neat to hear. That's cool. I didn't know you didn't realize that. I was trying to set you up. No, but that's cool. I'm glad that I got to share something with you. And it's because it's so important.

for these wild animals, especially if they're going to be going back into nature, which we would hope they would, it's really important for them to stay as close to their food source as possible. Absolutely. And so the fact that he has found these groups that are...

Katie (01:01:35.405)
Birds of prey that are based upon a marine diet that you can provide that to is even better. Because there's plenty of other opportunities similar to that, but that may not be what their normal diet is or even close enough so that those nutrients are still in the same cycle as they would be in the natural environment. Maybe a little bit out of kilter in the food web sort of things.

Probably don't have an osprey. In the tropic level. Probably don't have an osprey smoking a marlin, but you never know. Seeing crazier things out there. As close as we can get. That's awesome. Jeremy, that's time for today. One more question for you. Can you tell me what gives you the passion to keep coming back to the ocean to keep studying fisheries every single day? That is a super easy question. It is just my

general curiosity about the scientific world and the natural world. I always have questions. I always want to know more. I think anybody in the field that you talk to probably has that same desire. It's just what if, what if we look at this? What if I have a chance to examine that? Well, I wonder how they do that. It's just, there's always something to learn. There's always more to inquire upon. And that keeps me going every single day. I love it.

Excellent answer. Thanks so much for joining us today. You heard it here at KDC Sawyer podcast. Y 'all have a good one in tight lines. This episode is available on podcast listening platforms, as well as YouTube. If you want to see more photo and video content to support the conversation, you can check the description below for more information on Jeremy as well as the University of Southern Mississippi. Thank you so much for checking in and tight lines.