Is Bottom Trawling Always Bad? It Depends Where

0:00 off the south coast of England, about 100 kilometers out, there's a granite reef called Hog Frost covered in jewel anemones and corals. And on paper it had been protected for years, but heavy fishing gear could still drag across it. So is it really protected? In March 2024, that finally changed. And here's why where we fish matters as much as how much we fish of it. We're gonna talk about that on today's episode of the How to Protect the Ocean podcast. I'm your host, Andrew Lewin. I am a marine biologist and science communicator here to tell you all about the ocean, covering ocean news, ocean science, ocean conservation, the whole gambit, so that you can understand the ocean better and maybe lessen some of that ocean anxiety or climate anxiety you might be having, or questions around the ocean that you might be having.

0:49 I'm here to help answer any of those. So if you have any questions, feel free to get in touch with me. If you're listening to this on Spotify, there's a comment section, I'd love to hear your thoughts. If you're listening to this on YouTube, which I'll be posting, uh, this on, you can hit me up in the comments below. And if you are listening to this on your favorite podcast app, 'cause this is an audio-only podcast for most part, you can hit me up on my socials. The links are in the show notes. Now, we've been covering how many fish we take and, what else ends up in the net over the last couple of episodes. And on Monday, I talked to Dr. David Shiffman, who wrote Why Sustainable Seafood Matters, and you can pre-order that right now if you really wanna get into sustainable seafood conversation. Today's all about where we fish and what we do to the sea floor while we're at it.

1:33 it's gonna be an interesting show today, because there's a lot of, like, recent documentaries, ocean documentaries, that you've seen the footage, like a heavy net drags along the bottom, a cloud of sediment, and a scar on the sea floor, on the, documentary last year, Ocean, narrated by Sir David Attenborough, was a very enlightening, documentary for a lot of people. I took my daughter there, who's in wildlife biology. It was emotional. You saw this beautiful reef, and it was wonderful. And you saw, like, all these anemones, and it was very productive on the bottom, it was so, like teeming with life, invertebrates, fish, all this kinda thing. They mounted cameras on a trawl, and the trawl went right through it. And it was a protected area and everything like that, and it's just like, wow, it just destroyed everything.

2:17 You can hear the sniffles, and you see people crying, including my daughter, and even made me emotional to see all that productive habitat be gone Now, the message that the movie created it was simple. It was like, ban it. Ban it everywhere, but it leaves you to wondering, like, whether every piece of cod or shrimp you've ever eaten came from those bulldozed sea floor. Today I want to give you that clear picture, one that takes the harm seriously, that, of trawls, we know that it, but still leaves room for solutions that can actually be passed into law, To look at how we can better protect things in, like the items and the life in marine protected areas, as well as worldwide, and making sure that we are only trawling in places that it won't harm anybody, if we are trawling at all.

3:06 Now, I did my master's on marine protected area design, this is the episode where, like, I get to geek out a little bit, and I'm looking forward to that. So I want you to just go through, like, what a trawl net is, so a trawl is a net, like, essentially pulled through the water, and there are two very different kinds. There's a midwater trawl, which moves through open water and never touches the bottom, and then there's bottom trawls dragging along the sea floor, over sponges, corals, seagrasses or reefs. And they can do enormous damage to that habitat because once they go through and ruin that habitat, that, line, however wide that net is, will just scrape all that stuff off for the most part, it leaves these visible scars. it's basically clearing a forest, like, to catch rabbits essentially, that's what it's kind of analogous to.

3:52 That's the harm in the documentaries and in those places that it's real, Like, I wanna just kinda give context that usually gets left out. Bottom trawling provides about a quarter of the world's wild-caught seafood, about 19 million tons a year, and much of it comes from sand and muddy bottoms that recovery happens relatively quickly. And in 2018, a large study mapped bottom trawling in fine detail across many regions around the world, and in the regions studied, about 14% of the sea floor was trawled. It ranged from less than half a percent off southern Chile to 80% of parts of the Adriatic Sea Now, two findings stand out from this study.

4:33 Trawling happens in the same places year after year, and the regions were less than about 10% of the sea floor that was trawled almost always had sustainably fished stocks. So the more useful question is where, how much, and what's living there? 'Cause that's an important aspect, and that's why some bottom trawl fisheries hold Marine Stewardship Council certification and good seafood guide ratings. And it depends on the place and the rules. And this is a lot of where people have a problem, especially with the Marine Stewardship Council certification, because they're like, "Well, how can they say that trawling is okay? That they shouldn't be saying this." But I guess it really depends on where it's being trawled, and studies have shown that sometimes these areas are not, like, terrible.

5:17 In 2018, a team from Dalhousie University and Germany's GEOMAR looked at 727 marine protected areas across the European Union, and these were places governments had officially designated to protect ocean life. So the idea around these marine protected areas, Like, it's really two things. you're trying to protect biodiversity, so you're trying to protect all the animals and the habitats in there. But you might also be, protecting fisheries. So you have a specific commercial fishery or a number of commercial fisheries where this is an important habitat for those fish. And those fish can show in the number and the size, and then the idea is it'll have a spillover effect over the boundaries. So if nobody fishes within those boundaries, those fish will actually grow bigger and more of them, and they're gonna spill over because they have to compete for food and habitat, and they gotta look for some of those.

6:05 And the fishermen will be able to fish there. They found in this study where they looked at marine protected areas and what was happening in them, they found that commercial trawling it was happening in at least 59% of them. And on average, trawling was 38% more intense inside the protected areas than in the nearby unprotected water. In the most heavily trawled areas, sensitive species like sharks, skates, and rays had declined by 69%. And one of those authors, Boris Worm, put it this way: "- when industrial use is elevated rather than reduced in protected areas, we are not getting the conservation outcomes that we need." We call these paper parks, when you're not really protecting what's there. You're allowing some kind of extractive activity to happen, whether it's fisheries or oil and gas or whatever that might be.

6:50 And it just becomes a line on the map, a boundary, an invisible boundary that nobody's really paying attention to with the same activity going on inside it, which is what you were supposed to stop. And it isn't only Europe that it was happening. Around the world, MPAs get announced with great fanfare, and then left without any type of rules or enforcement or funding. We've talked about that on numerous times on this podcast. Some are even, like, drawn in places where the species like, they were meant to save doesn't even live. And so MPA is important, but it's also important to have the data, to have the management, to have the enforcement. And when an MPA is done well, the results are remarkable. A global review found fish biomass about 570% higher in no-take marine reserves than in unprotected areas, I should say that figure was corrected in 2025 from an earlier higher number, so science is already correcting itself, and that's a good thing, to be honest.

7:43 Now, a study in 87 MPAs worldwide found five features that make the difference: no fishing allowed, strong enforcement, more than 10 years old, larger than 100 square kilometers, and isolated by deep water or sand. MPAs with four or five of those filters had five times more large fish and 14 times more shark biomass than fished areas. Let's go back to the 59% of the MPA studies had only one or two of these features. And to be honest about the limits, an MPA can't stop warming water, acidification, or an oil spill drifting in from the outside, or plastic pollution. It's a powerful tool for biodiversity and fisheries with a specific job, but it can only do that if it's properly managed and everything else around it is good.

8:28 It kinda leaves it for the, ecosystem to just kind of recover on its own. Now, England has dozens of marine protected areas in its offshore waters. So for years, many of them allowed bottom-towed fishing, gear to be dragged across the very habitats they were created to protect. And in June 2022, the Marine Management Organization, the agency that regulates English seas, brought in its first bylaws banning bottom-towed gear in four offshore sites, including Dogger Bank, a huge sandbank in the North Sea, and the canyons, deep underwater valleys of the southwest. In January 2023, it proposed going further and opened a public consultation. Anyone can comment, fishers, scientists, conservation groups, ordinary citizens.

9:11 And on March 22nd, 2024, the bylaw took effect. Bottom-towed gear were banned over sensitive reef habitats in 13 more marine protected areas, covering about 4,000 square kilometers. Places like Haig Frass, a granite reef with jewel anemones and cup corals, Cape Bank and its sea urchins and cushion starfish, Goodwin Sands with the sea fans it was very important to protect these. So together, those bylaws protect almost 18,000 square kilometers of English seabed from bottom-towed gear. The agency reported high compliance with the rules in the first sites, and so with very few infringements detected. that's a really good thing 'cause the enforcement's there. And that is what matching the rules to the habitat looks like.

9:52 Trawling carried over sand and mud elsewhere, like, that's fine. It stays off the reefs that can't take it, and it allows for, like, mud habitats and sand habitats to recover because there's no overarching habitat, like a sponge reef or, like, very sensitive reefs with anemones and all these kind of things that will take a long time to recover. What's nice about this, it also happened through a public process. People showed up, they commented, and that matters for today's call to action, and we're gonna talk about that in just a sec. Now I just wanted a quick turn to talk about aquaculture because the same principle applies in aquaculture. In 2022, the first time ever, farms produced more of the world's aquatic animals than the wild fisheries did, 51%, about 94 million tons.

10:37 And if you eat shrimp or salmon, you've almost certainly eaten farmed seafood. I think in Canada or here in Ontario, most of our salmon, unless you catch it yourself, is farmed. It is very expensive to try and get wild caught, and it happens every once in a while, but most of it's farming. Fish farming gets painted as all good or all bad, and like trawling, it depends on how or where it's done. What fish are fed, how waste and disease are handled, whether farms escape into the wild. Now, there are some ways that, aquaculture's not being done to the best of its ability, and there are a lot of people who are very emotional about how it's being, rolled out, how it's being enforced, all that kind of stuff. And so I get, some of the, consequences to that and how people look at that.

11:21 But the quick way to tell is, you wanna look for Aquaculture Stewardship Council, the ASC, that kind of label, just like the Marine Stewardship Council. Best aquaculture practices, BAP, is less strict and still a lot better than nothing, though, seafood guides rate farm products, too. So the Seafood Watch, your Marine Stewardship Council, OceanWise, app, those all work. Now, one rule of thumb that works for farmed and wild seafood is doing it right costs more, producers who do it right tell you about it loudly, like, because it lets them charge more. And if the package is vague about where and how something was produced, that's usually a sign. It's usually, like, right then and there because it's a higher price, so they wanna make sure that you know exactly where it comes from.

12:03 Here's where I want you to take from this episode, The next time your government proposes a protected area or reviews the rules of an existing one, submit that comment during public consultation. It doesn't matter if you're a fisher or you live near the ocean, or you know anything about marine science or marine conservation. You don't have to be a marine biologist to have this public comment. It's for everybody. It's for public. Whether you live in the country or even outside the country in a lot of places, you can have your say. If you care about the ocean, you care about how things are done, and you want things done right, 'cause when they're done right, they work, well, let's get them done right, keep it simple when you do your public support. Say you support the protected area and ask that the rules keep bottom trawling and other destructive gear out of any kind of sensitive habitats.

12:44 Most countries post these consultations on their fisheries and environment agency website, so sign up for those alerts from those websites or follow a local ocean group like Oceana Canada, if you're in Canada, or any, Oceana wherever you live, they'll track them, and they'll kinda help you with that. Now, the difference between like a paper park and a real one is essentially how the rules are enforced and the rules that are within it, right? Rules get written in consultations, and then consultations count the comments. So it's an important thing to know that when you go to this public comments, that, that's a significant part of this process. Now, that's the end of our episode, We've been covering all the harms and the fixes to make sure our seafood's sustainable. So, next time if it's you at the seafood counter, we're gonna talk about that tomorrow.

13:26 Labels, the apps, and how those choices actually change what's in the ocean. We're gonna talk about that tomorrow 'cause it's really, really important. But kind of thing I wanna leave you with here is, like, I want you to understand, like, the Hag Frass, like this sensitive marine protected area. Hundred kilometers off Cornwall, pink sea fans sway in the current, and a jewel anemone opens. No chain has come across this reef since 2024. It's developed, it's established, and it brings habitat for so many other fish species that allows fisheries to continue and be sustainable. It's such an important part of conservation. You protect the right places, write the right rules, and the sea floor will grow back.

14:10 Place by place, the ocean and the dinner table can win. They can both win. That's an important aspect to remember for this episode. If you are listening to this on an app or a platform where it allows comments, please reach out to me. I'd love to hear what you think of the episode or if you have any questions. And of course, if you are listening to this on your favorite podcast app audio only, I would love to hear from you. My socials are in the show notes. Hit me up. Thank you so much for listening. I'm your host, Andrew Lewin. This has been another episode of the How to Protect the Ocean podcast. Have a great day. We'll talk to you tomorrow, and happy conservation.