Eels

Alex Re (00:00): Hello, welcome to On Wildlife. I'm your host Alex Ray, on this podcast, we bring the wild to you. We take you on a journey into the life of a different animal every week, and I guarantee you, you're going to come out of here knowing more about your favorite animal than you did before. This week's animal may be a little slimy, but they're also really interesting, and this is partly because parts of their lifecycle are still kind of a mystery to us, but we'll talk about that later on in the episode. So grab your scuba gear because we're heading under the ocean to talk about eels.

(00:53): Eels belong to the order Ola forties, and there are around 800 different species. They can be found pretty much anywhere in the world. And what's really amazing is that some species can live in both fresh and saltwater. Some of their closest relatives are carp and catfish, and the largest eel species in the world is the European conqueror. It can get to be over five feet long and weigh around 150 pounds. That's massive. Now we've got a lot of really interesting information to talk about with our guest, Dr. Willem Dekker. He's been studying eels for around 40 years, so he's got a lot of great stuff to tell us. He'll mainly be focusing on the American and European eel today. Let's hear about how he got started working with eels.

Willem Dekker (01:44): I'm a classical biologist, field biologist, and I've got an interest in mathematical modeling in biology. So where can you combine classical field biology and mathematics? And my interest was especially in systematics of the animal kingdom. So then you end up in the marine environment and if you add mathematics, you end up in fisheries management. For a long time, fisheries management has been based on mathematical models. So I went to the Fisheries Institute here in Netherlands as a student, and when I had done my student's job, they wanted to keep me and they had only one position to offer that was to work only. So it was purely by accident that I got involved in. And soon after, the budgets were cut and the idea was that after three or four years, I would move on towards the full marine fisheries. 40 years later, that still hasn't happened.

Alex Re (02:45): And there's a lot of problems that Willem has had to solve throughout his years working with eels.

Willem Dekker (02:51): I've enjoyed that so much to go from basic biology. How does the animal live? How does the fishery work? How do the fishermen live? That's quite a problem. How does politics deal with a complex problem like the e management? I've been involved in all those things over the years. There are no five years I've done the same as I did before. Well, no, I've once stopped in exercise. When I moved from the Netherlands to Sweden, then I had to redo what I already had done, and I didn't like that at all. I liked doing new things. 40 years later, here I am still doing my first job and still enjoying it.

Alex Re (03:32): Now let's get to talking about eels. I asked about some unique adaptations that they have.

Willem Dekker (03:39): Let me begin with the most controversial one. It's a fish, but it's absolutely not a fish. It's a snake. They live in the water, but it's one of the rare fish in, well, in the temperate zones, at least the water on a routine basis. Don't expect to find a new on the street. That doesn't happen, but you find them in the terrestrial habitats after the rain or after the spring, flooding has gone take a little bit of the marine of the terrestrial production, and that makes it a very productive fish. The second thing is I've been working in Europe. You're in America. There are two different species in American EEW and European eew, but they are almost identical. I can't see the difference. I know a few tricks, but that's it in Europe, from the north cape down to say delta and it's all one and the same fish, and you can find them in the freezing north and in the desert in Egypt. And it's the same animal, both of them on the rim of the terrestrial ecosystem. Tremendous adaptation to Unbelievable.

Alex Re (04:52): That's amazing. That's really amazing. Yeah,

Willem Dekker (04:56): And I can exaggerate a little bit. It's a predatory fish, but if you see him predates anything, you are ashamed to work on these species. It's so clumsy. They can eat bottom food, but if you see them collect the bottom food, you'll feel ashamed. It's so clumsy. Okay, whatever. They can do it all everywhere. They're a little bit clumsy, but to master it all, that's truly a woman.

Alex Re (05:25): Yeah, absolutely. And another really interesting and crazy thing about them is their life cycle

Willem Dekker (05:32): Mid 18 hundreds, so that's more than 50 years ago. And people were just starting to understand how a fishery produces 1840. Some Frenchmen in the eastern part of France had found out how to reproduce trout, and that was the very first time they could. There's a story behind that, and what they said is, okay, we can reproduce pike, we can reproduce trout. We cannot reproduce salmon. They still hadn't master it and we cannot reproduce ew, but we'll find out soon. And the whole optimism of say, five years and we will be able to do it five years later, they managed to reproduce the salmon. So even the more difficult fish was within their options, but they didn't manage. And then they start wondering, where does this horrible animal reproduce? Do they reproduce at all? Is it something we don't recognize? And then from 1850, well up to today, you see that they don't reproduce in the river.

(06:38): That's clear. Then they say, okay, it must be in front of our coast. Well, it isn't in front of the coast. And they say it must be somewhere deeper, a bit offshore, but it isn't deeper shore. And then they say, oh, maybe in the ocean. And okay, further and further and further away until in, what was it, 1906, finally a Danish scientist thinks he has found it. He finds them in sargasso sea. We think they're born in sargasso. We still haven't seen it. Then you have a crazy lava. It's very flat and thin and jellyfish like, and it lives probably for two or three years, arrives on our coast, transforms into what we call the typical EU model, stays here for, well, anything between five and 20 years. If you go to southern Europe, it's mostly five. If you go to the north, it's mostly 20, depends on temperature. And then they have to go back to the sea to travel 5,000 kilometers on their way in. They had to flow with them on their way back. They have to flow against them 5,000 kilometers swimming against to mate only once and then you die.

Alex Re (07:54): It's amazing what these animals go through to reproduce and that we still haven't seen it ourselves, but our fascination with this is actually taking away from people focusing on their conservation.

Willem Dekker (08:07): The intriguing issue of something you can't solve attracts an awful lot of attention in my career. What I noted was that all my predecessors and all the colleagues around them when they entered the ocean, they were lost forever. They never came back. They kept working on the ocean. So in a very early stage, I've decided not to work on the ocean. I know it's an unsolved problem, but I won't work on it.

Alex Re (08:36): And what we don't think about is how important eels are to the ecosystems that they live in. We'll talk about that right after the break time. For our trivia question, which country has the most biodiversity in the world? The answer is Brazil, probably because it's home to a good amount of the Amazon rainforest. So why are eels important to the ecosystems that they live in?

Willem Dekker (09:34): It is a species, a fish that moves in and out. It comes from the sea, it moves into fresh water, it moves back again. There are many fish that do that. Different herring species. There are many fish that do. So we have lost salmon and trout. We have lost many of them, and that's because we have dam the waters. We have built hydropower dams. We have lost most of those fish, and the eel was the one that was still going strong for a long, long, long time. Long after the odds were already in decline, the eel was still there. So it is in a way, the last man standing eels were a dominant part of the ecosystem. There are many areas in Europe where eel has been more than half the fish biomass in the water. That's long gone. So nobody remembers that nowadays. But the old data indicates something in this order of magnitude losing half your biomass. I'm not saying it's not replaced by another fish, but it's replaced by another fish that's not the same as so you have lost already quite so much. It has an important role for many predators, birds, authors. So E in a way is the integration of it all. Can you do without E? Oh, yes, definitely. It would be just another step. You are losing another important factor.

Alex Re (11:03): Yeah, absolutely. And you talked a little bit about how it used to be such a common fish, like 50% of the biomass, and now it's declining. So what are some of the problems that eels are facing?

Willem Dekker (11:17): There are two things. One is if I look at the long-term data and long-term for me is from 18 hundreds onwards, you can see that the stock was in decline for decades, for at least a century, possibly for even more. On top of that, in 1980, the abundance of the youngsters coming from the ocean was still very high. And then from 1980, it suddenly started to collapse. 19 80, 19 84 was my first year in office. So I haven't seen anything. I've seen it in my youth, I remember how it was, but in my career, in my professional career, I've seen nothing but a decline that came on top of the decline that was already slowly go on for at least a century, but now you're suddenly in very critical waters, of course, because it's going so rapidly, the dumpsters from the ocean going down, and then on top of that, the old slow decline in continental borders.

(12:20): What is the reason? It's difficult to say habitat loss is an important factor. My house in the Netherlands is just above sea level, but my garden is below sea level and the water is pumped out and therefore I have a garden. If you want to restore that habitat, I will lose my garden and probably the house will be gone. That's not something we're going to do. You don't drain half of the Netherlands because you want to save the, so habitat loss is not just something theoretical. It's very practical. All around us, all the dams have contributed, pollution has contributed. Overfishing, the simple overfishing has been a very important factor in which it is not only commercial, but also the regressional fisheries.

Alex Re (13:07): Wow. So they're facing an insane amount of problems, but there are some things that are being done to help.

Willem Dekker (13:13): There is commercial fishery and you must make sure that a fishery is limited. I don't say stopped, but limited. You want a certain number of spawners of mature animals to go back to the ocean to give you a new year class. If you leave it to the fishermen himself, there's nothing that will stop him. For him, any eel going to the ocean is a loss. You can find this already being discussed in 1870, but no one ever managed to do anything. And my job, my personal job in this whole debate about EU has been to initiate the awareness and to initiate the coordination. If you want to stop to be protected, you must limit your fishery, and I must limit my fishery and we must somehow coordinate between the two of us. That process for the whole of Europe. Well, I've been initiating that process and I've been deeply involved in setting the standards.

(14:16): What is adequate? That's one thing. The other thing is the habitat lost is partly due to the habitat is simply gone where the marshland was. You now find my backyard. That's more or less lost forever, but many places there's a dam and the habitat as such still exists, but you can't come there anymore. And what people have done, and that's very old already, is to build a structure, a ladder across the dam. And what you try to do is to make it in a way that the EU itself can climb the ladder and can come over to dam. And what people have done for a long time starts in 1840, is you pick up the EU in an area where they are very abundant and you bring them somewhere else and deliberately saying 1840. That's the beginning of the steam trains. The steam train has enabled the long-term transport of Youngs. Eventually that became, you catch the young in France, you transport them by train, by airplane, and then again by train to Eastern Russia and well, it worked.

Alex Re (15:33): That's really interesting, and it seems like there's a good amount that's being done on a large scale to help eels. What is something maybe the average person can do to help eels?

Willem Dekker (15:45): This is a very politically sensitive question. I understand. What can I do myself? I understand the question, but what people have been advocating is let's stop the consumption of it completely, and that is something you can do yourself. It sounds convincing. I don't eat it anymore. In reality, you save very few eels and the major impacts are not in consumption, but in the habitat loss and title power generation and things like that, what we see is that in countries where they have closed the fishery, they lose. Interestingly, this is a problem that is so big covering all of Europe, covering so many aspects and so many different stakeholders. This isn't something for the small scale approach. You have to have a pan-European approach and probably even a worldwide approach. Otherwise, you won't be able to do anything.

Alex Re (16:50): But even though it's such a large issue, you can make a difference by influencing people who are in powerful positions.

Willem Dekker (16:58): While it is a much bigger and international problem, the path I have followed is if it is not a small scale problem, but it is a political issue, then I move into the political advising. Well address the problem where it can be solved instead of where I am myself.

Alex Re (17:20): I want to thank Willem so much for coming onto the podcast and giving us some really interesting information about eels. They're facing a lot of problems and we definitely don't talk about their issues enough. If you want to help eels, some organizations that you should take a look at are the Sustainable Eel Group, zoological Society of London and The Nature Conservancy. Thank you so much for coming on this adventure with me as we explored the world of eels, you can find the sources that we use for this podcast and links to organizations that we reference at onwildlife.org. You can also email us with any questions at On Wildlife dot podcast@gmail.com, and you can follow us on Instagram at On Wildlife, or on TikTok at Wildlife. Don't forget to tune in next Wednesday for another awesome episode, and that's On Wildlife

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