| INTERVIEW
TRANSCRIPT - Dr. Les Watling
What I’ve been doing is looking at what happens when a trawl actually passes over the surface of the sediment. This is a little bit different than looking for large things that have been crushed and smashed, but rather looking at the structure of the sediment itself and how it’s altered. And I’m particularly interested in how habitat gets altered for all of the small things that live in this muddy bottom. I got started in this whole business actually in mid-1990s. Because I had found this place where these large sponges were present and I had a friend who was a sponge taxonomist and I took him out on a cruise with a submersible and put him down on the bottom and asked him to collect the sponges, take them home and identify them, so we would know who they were. And when they came back up, they had no sponges. And so I asked to see the videotape. You know what had happened? Could we have been in the wrong place or whatever? And it was clear that the whole place had been trawled. All the large sponges that we had seen in the tape from 1987 were gone.
There is this general perception that when trawls or scallop drags or whatever goes across sandy bottoms that those devices only do what storms do. They stir the sediment up and everyone gets kicked up into the water and they settle back down and think, "okay we’re all right." But in fact, a large number of things happen. Even in sandy bottoms, the sediment is structured in such a way that the good stuff to eat. If you’re an animal living in the sandy bottom you’re looking for high quality food — otherwise you have to eat a lot in order to digest out of this sediment what you need — so the high quality stuff is all the stuff that has settled from the water column onto the surface of the sediment. The key for understanding what happens when scallop drags or trawls go over this bottom is that it kicks all that stuff back up into the water and the tide carries it away. We’ve in fact documented this very well here next to the Darling Center using a scallop drag. And doing a lot of careful chemical measurements and what not, we see that the top two to three inches of the sediment is completely carried away. So all the good food value is gone. In muddy sediment, you have the additional complication of the fact that to live in mud, animals have to make burrows or tubes. They have to do this because they need to breathe oxygen. And there is no oxygen in the sediment. So they have to maintain an opening to the overlying water in order to get enough oxygen to live. When the trawl comes along, we know from all the work we’ve done with x-rays that the entire upper 3-5 inches of the sediment — all the tubes and burrows and everything — gets obliterated completely. A lot of that mud gets kicked up into the water and settles back down again. So you’ve lost food value. You’ve lost dwelling structures, homes, for all these animals. All these things have been changed. Then on top of that, sediment that has sat there and gradually lost the water just due to settling by gravity has suddenly all this water back in it. And what most people don’t realize is that the reason why animals live in sediment rather than up in the water is that they are not swimming. If you put all that water back into the sediment, you’re essentially forcing an animal to swim in this mud. And they can’t do it. And so an awful lot of animals die under those conditions. So trawling in muddy and sandy habitats is not benign. It actually makes a very big difference to the habitat; it’s just not so visible.
What’s so bad about it is two things really. One is that part of our objectives as scientists is to document, monitor, and preserve marine biodiversity. And clearly, we’re losing biodiversity when these habitats are altered in this way. From the fisherman’s point of view, there is also a reason they should be concerned. And that is that all this small life is basically the food for the very young stages of all the fish they are trying to catch. It’s like disturbing over a cornfield two weeks or three weeks after you’ve planted the corn. What’s the point? The corn will never grow. And young fish need someplace to feed and some food to feed on. And this is basically the food source. But besides that, there is this question of habitat integrity and whatever services that those habitats might perform which we don’t know about at the present time.
We use cameras primarily on remotely operated vehicles or ROVs. And also we’ve used cameras mounted on sleds, which on muddy bottoms, is a fairly efficient way to get a good picture. No matter what kind of camera system you use, you can see a number of effects of a trawl having passed over an area. The most obvious things are what are called doormarks, which is where the doors that are used to haul the auto-trawls open make fairly large gouges in the sediment. They’re basically like a plow going across the mud, turning up the mud on one side and leaving a huge trough on the other. And those are quite visible. So as soon as you see those, you know you’re in trawled area. We’ve also discovered some other smaller things with shrimp trawls, for example, on muddy bottom where the mud seems to go into the net even though many shrimp fishermen will tell you that they’re not dragging the bottom very hard. What you see when you go in an area that is freshly trawled are a bunch of little mud pyramids. These mud pyramids seem to be mud that has gone into the net and then been squeezed out through the mesh. And one place where we investigated this we saw that these mud pyramids lasted for about a week or ten days and then gradually got worn down probably by the animal activity in the area. But it’s quite obvious visually when you go across an area that’s been trawled. I’ve looked at a lot of stuff in the Gulf of Maine in particular. I can pretty well tell anywhere in the Gulf of Maine I can tell an area that’s been trawled just from camera pictures.
A good example is where rock hopper gear is used. And you’ve probably seen this video of roller gear, rock hopper gear going across the surface. And every once in awhile, the foot-roll with one of the large rollers on it will get caught on a large rock of say, 2 to 3 feet in diameter. Instead of going over it, it gets caught on it then it pushes it over the bottom. Eventually that large rock will hit something else and then roll and the whole gear will go up over it. You can see these kinds of marks when you’re diving on the bottom, either in a submersible or with a ROV. You can see large troughs or gouges behind big rocks. You can see rocks that are standing up on end in what would seem to be a rather unnatural position. You can see rocks where all the life that was on the top of the rock is now sort of under the rock and now the top of the rock is bare. There is lots of visual evidence that you can use to determine whether an area has been trawled or not. We’ve gotten pretty good over the years now that we’ve looked at so much videotape. We’ve been doing so much diving with these devices that we can pop down into an area and we can tell within a few minutes whether the place has been trawled or not.
Well there’s a big problem here and that most of the animals we know something about in cold water are long-lived. Unfortunately, we don’t know very much about very many animals. So we’re guessing that it will take these communities of sponges and corals a very long time to recover. We don’t see rapid re-colonization in areas that we’ve studied. In fact, one place in the Gulf of Maine, the place was trawled somewhere between 1987 and when I went back there in 1993. In 1987, it had very large barrel sponges, foz** sponges — all sorts of large organisms living on the rocks. Every possible area of surface of the rock had some living thing attached to it. When I went there in 1993 that was all gone. It was completely gone. And I’ve been back as late as 1997, and there is still no sign of any recovery of any of that large stuff. What we do have in fact is like you would see in an old field. You have all the little weedy species, small things call hydroids. But instead of having 10 or 15 species, you have one that covers completely the surface of the rock. So we found that the biodiversity of the trawled area was about half of the un-trawled area. And none of it was large things. I have no idea how long it will take for the larger things to gradually come back to that area.
One of the concerns that we have about losing this large structure is we actually know very little about nursery grounds of the commercial fisheries. In fact until a few years ago, we didn’t even know where cod went when they landed on the bottom after leaving the plankton when they were a month or two old. No one actually knew where one-year old cod were. And I think that can safely be said for many other species as well. So we don’t know what their habitat requirements are. What we do know is that in the 80s when we were diving in these areas that had these complex habitats is that we saw all these small fish. And now when we dive in areas that are un-trawled because the boulders are too large or something like that for rolling gear to get in there, what we see are very large numbers of small red fish. For example on our most recent cruise, that was probably the key organism that we found in these rough bottom areas were hundreds and hundreds of really tiny red fish. And I think if you go to a few remaining areas, where you have this kind of complex habitat structure and we’re able to have a look at it, you would see these kinds of things. But since so much time has gone by with all of this roller gear being used, we have very few of these places left. We don’t know how they were used as refuges. But my guess is they were probably very important. I personally think that the final collapse of ground fishing in New England was due to the introduction of roller gear and the destruction of what were otherwise natural refuges.
Yeah that’s a little bit of a hard number to come up with, but I think we can take a sort of broad-brush look. The Gulf of Maine is unusual for the East Coast of the United States because it has so many different kinds of habitat. If you go from the top of Georges Bank all the way to Florida, by in large you’re dealing with sand. But in the Gulf of Maine you have muddy basins. You have rocky ledges and ridges. You have old gravel moraines left by the glaciers that have rocks of varying sizes on them. Then on top of that, you have very different kinds of water types. So if you take sort of the cold water layer in the Gulf of Maine which covers the middle 1/3 depth-wise, say from 50 meters down to 200 meters, within that layer you have most of the bottom that supports the ground fishery. And I would say about 2/3 of that was trawl-able before rock hopper gear came along. Meaning that it had either fairly small cobble pebbly bottom or was mud. Of the remaining third, some of it is just open rock ridge where you couldn’t really drag a trawl up. So we’re down to probably that might make up 5 or 10% of that remaining third. And so, most of the remaining third has been opened up to trawling as a result of the development of rock hopper gear. So, if you take the Gulf of Maine as a whole, you would have had about 65% of the bottom area that would have been available to trawling before rock hopper gear came along. With the advent of rock hopper gear, about 90% of the Gulf of Maine bottom is available for trawling. That leaves 10% that is untrawlable; that is not very much.
Well, I’m not a fisheries biologist. But common sense would tell me that you can’t raise a large stock that would be under significant fishing pressure on a very small area of the bottom of the Gulf of Maine. You have to just step back for a second and think about what these fish need when they arrive on the bottom, out of the plankton. They’re small, a few inches, an inch or two long. They are easy prey for other fish, particularly silver hake. But all of the other fast swimming cod-like fishes all prey on small fish. So they need a place to hide. They need things to eat. Fish have to eat everyday. So there has to be available prey in very large numbers to support young fish when they arrive from the plankton. It seems to me that if you take a very large area like the Gulf of Maine and you have in it these little tiny islands of untrawlable bottom, it’s going to be very hard for the fish to find them. First of all, those little islands are not going to support very many fish. So, just from that, just as a total common sense — you don’t have to do any mathematical modeling here — it’s fairly simple to think about the fact that you need larger patches of bottom that are undisturbed to support these young fish.
A good part of the problem is that as all these fisheries were fished out in shallow water, people moved more and more into deeper water. Moving into deeper water meant the development of larger, heavier gear. Which meant the financing of very large and very powerful vessels to pull this gear. And now what we’ve seen is an effort on the part of not only fishermen but in fact of governments putting money into the development of these large vessels and this large gear to fish ever deeper. I personally think this is an ecological crime. I think that these areas have been undisturbed for millennia. They are not adapted to any disturbance regime that we know of. No natural disturbances occur once you get below 700-800 meters. And we also know that the organisms that live here are very long-lived. And so one sweep of any of this gear through this bottom area will leave a mark for centuries probably and maybe a lot longer. And the fact that people are being encouraged by financial incentives to fish in these areas I think is really unbelievable and unconscionable and should be stopped.
My inclination is to say that the reason why the rebound has taken so long is that there is nowhere for newly recruited cod to go to survive. That’s because I have a habitat perspective. Mathematical modeling tells you that you should get a certain percentage of fish. If you have certain stock of reproductive age animals, they will reproduce a certain stock of eggs. You will have certain losses, some percentage loss all the way through this business until you get back to an adult cod. The problem there is that as other aspects of the environment have changed you have things like the North Atlantic oscillation that may determine aspects of the planktonic food chain. You have habitat loss on the bottom. You have lots of other sort of externalities that come to bear on the changing the numbers in this percentage loss trickle down that everyone uses. Something like 95% of the cod eggs that are spawned every year are just lost. The question is if you ruin the habitat for these young animals as they land on the bottom do you change that number for 95 to 97? We don’t know those kinds of answers. It may be that it’s that last 2% or 3% that’s going to make all the difference in the possible rebound of the stock. That’s what’s not been looked at. And I have a hunch that the fact that we lost so much of the habitat that could be nurseries is going to drag out this recovery for a very long period.
Scallop gear and auto-trawls actually work in quite different ways in terms of what they do to the bottom. From what we’ve documented so far, when a scallop trawl drags, they are very heavy and they plow along the surface. Some people think they actually slide along the surface, but in fact they dig into the bottom a few inches. In doing so, they actually put quite a bit of sediment up into the water. You can actually see furrows that are left by the scallop gear after it’s gone across the bottom. They’ve been documented in many instances, not just by us, but also by others, as being about 4 inches deep. Auto-trawls are interesting because they can be rigged in many different ways. And the degree to which they dig into the bottom really depends on how they’re rigged and how they fish. We’ve looked now at shrimp gear in the Gulf of Maine area, which is a cold-water shrimp fishery, which occurs primarily on muddy bottoms and the mud is very fine, and that gear is supposed to slide along the surface. But we know in fact that it digs into the bottom from video work that we’ve done. Other kinds of auto-trawl gear, you can rig the footrope in different ways so that it basically pulls over the bottom. And clearly rock hopper gear is just a modification of an auto trawl so that it supposedly rolls along the bottom and actually rolls over the stones and other large structures. The problem is that it actually snags onto things because stones are not perfectly round. They have angles. They’re sometimes at a slight angle to the sediment and can get caught. The other thing that we’ve seen with rock hopper gear is that there’s an impact of the net as well. Most people haven’t really paid attention to it. And that is that the net acts like sandpaper as it pulls over the structure. And that, I think, is responsible for an awful lot of the large things that are knocked off the surfaces of the rock.
With scallop dredges, the impact is greater on a single pass because the dredge is so heavy and it literally destroys everything in its path. It leaves very little structure standing. It may take several passes of an auto-trawl to do the same thing.
Short answer — no. The biggest problem that I see with the way the fishery management system works today is that there is no chair at the table for someone who is interested solely in marine biodiversity. If I wanted to make a case that an area of the sea bottom should be protected because there is an unusual, interesting, rare kind of species that lives there that has no connection that I can establish whatever to the fishery, there is no way for that to happen. I suppose there’s one way, if I could prove that it was in danger of going extinct, I may be able to get the area protected through the Endangered Species Act. But the way ocean management has been set up in this country the fishery management councils almost de facto are responsible for managing any living thing on the sea floor. And I think I can say unequivocally that none of those people know very much about invertebrate zoology and therefore know almost nothing about all the other organisms that live on the sea floor besides fish. So there’s no way really for me to take a concern that I have about any small organism and have it dealt with in any way.
I think this has really been the case of sociology trumping biology. I think that there hasn’t been the political will to manage the fishery as a fishery in terms of the health of the fishery. With fishery production as the sole goal, there has always been in our system of managing fisheries, the competing needs of human resources with natural resources. And my sort of amateur look at this over the years says that human resources have always won out over natural resources. That seemed to me to be a recipe for disaster, which is what we have.
It does call for the precautionary principle and it does call for ecosystem-based management, but I haven’t seen any evidence of the precautionary principle being applied. And what’s happened with ecosystem-based management has been the definition of essential fish habitat. And for the most part, that’s single fish species-based. It includes very little of the natural world outside of fish. A good example would be there are lots of maps that’s been produced about where these fish are and the fisheries service, to their credit, has been very good at documenting where all the fish species are or have been over the years. What they haven’t done is documenting the habitat in those places where those fish are. As a result, we don’t actually know that much about the ecosystem requirements.
I think that the best thing to do is to match gear to habitat type. And on top of that, maybe even stay out of some kinds of habitats. See if we knew where the nursery areas were, I don’t think that anyone would be able to make a compelling argument that we should take a trawl and trawl through nursery areas. Everyone understands the importance of nursery areas. We just don’t know where they are. That’s one. On the other hand, if you knew that nursery grounds for example were fairly wide spread and had all this complicated habitat structure, you might then suggest that you fish in there using some kinds of gear, perhaps long lines, perhaps not, perhaps traps. There are other ways to catch fish that are maybe more labor intensive but will still produce some catch and yet leave an environment that will continue to produce some fish. It would be a helpful thing to do. So I think you could actually do this. There are ways to match gear to habitat type. I personally think that that’s the one single thing that could done that could make a big difference that hasn’t been done at all. No effort in that way whatsoever. It’s just too bad.
Well you know here’s the thing, there are lots of areas in the Gulf of Maine that were too rough to trawl before rock-hopper gear. So what did they use in those areas? They used hooks and lines. And those areas produced lots of fish. That’s why they still were in fact refuges. They were being fished but there were still refuges because the habitat was still being maintained. People have been contacting me about what should we do about gear? Are there ways we can modify trawls? In fact there was a recent initiative in front of the New England Fishery Management Council about changing the size of the rollers on the rock hopper gear. And I just thought well all right this is an incremental step but it probably isn’t going to do much good. All it’s going to do is shrink the un-trawlable area by a very small percentage, a half percent maybe. It’s not going to make that big of a difference. But if you got rid of rock hopper gear all together, then you go back that 65% that was trawlable and you leave 35% that’s un-trawlable. Now we’ve got a balance in this system that might mean something, that might make some difference. But I don’t see that happening any time soon, unfortunately.
Yeah, that’s one way to deal with it. But I often don’t take that approach because not all organisms are important to the fishery. And see that’s where I think we have to back away from the ocean as just a producer of fish and look at the ocean as a body of water that sustains all life. And it really bothers the hell out of me that a lot of people don’t really care about all these other things that we have in the ocean. And yet they’re part of the legacy of evolution. I mean why are we willy-nilly wanting to throw those things away? Or not even recognize their existence, which I think is probably even worse. I’ll give you my spin on biodiversity some time.
People say well why should we protect these species? Why do we care whether these species are going extinct? And everyone comes up with these sort of well there’s ecosystems services and there’s the potential for the cure for cancer and all this stuff. But I think that actually the issue is much more fundamental. And that is that we live as far as we know on the only planet that has living things on it. And we don’t know whether in the end if this will be the only planet or whether there will be others. But in the meanwhile this is what we have. And we’re fortunate to be here around at a time when we can understand what three and a half billion years of evolution has produced. So what I use as my example is the fact that what we see today is the end of a long series of evolutionary processes. We see all these interesting very specialized animals who are the product of evolution. It’s a marvelous process that’s produced animals that can do some pretty amazing things. And a lot of them are very, very tiny. And the analogy I would have is if you took a library that has in it — like the Library of Congress — everything that’s been written and if you think of those things as the end point of centuries of learning, but you said well what do we need this library for? It’s taking up too much space. So we’re going to go to the library and we’re going to take every fifth thing off the shelf and we’re going to take it out in the streets and burn it. People would go nuts. But that’s essentially what we’re doing when we’re destroying these species that are at the long end of evolution. We’re losing our record of how life has evolved on this planet. And I find that pretty sad that people don’t really care that much more about it. They don’t have to understand it. They don’t have to even know it. They don’t have to know all these details. But in the back of their heads, there should be an appreciation for why this has happened. And they should be willing to take the steps to protect it. And that’s what I don’t see which is too bad. But I find that analogy works with most people that I talk to sort of on the street or whatever, people who don’t know any biology.
By in large, there’s no one really evil in this whole business. You have a bunch of well-meaning people behaving according to the paradigm they were taught. That’s what it comes down to. They’re behaving according to whatever the ecological system was in the day that they did their Ph.D. work. That’s what they know. That’s the framework they operate in. And in science generally that’s the case. It’s not just fishery science. And it’s the occasional person who steps outside that framework later in their career and says maybe we’re doing things in a completely wrong way. And we need to take a fresh look. And the whole field eventually agrees and takes this little turn to the left or right and on they go in another direction. But either these big advances are made by graduate students or people right out of their PhDs or they’re made later on by someone who realizes that the way things have been done wasn’t getting you close to the answer you needed. And what I see in the fisheries business is a whole bunch of people who are trained in the 60s. I mean that’s why the Ricker Population book. That’s why we called it the bible for a while. Because everyone learned their population mathematics from that book and others like it. And that was it. There was no mention if you look in the index in that book you won’t find the word habitat. I guarantee it. And in many of those books, the habitat is just not important. It’s this cute little black box that young fish come out when they’re a certain age and then they become recruits to the fishery, which is a term that took me a long number of years to learn. Which is a very different use of the word "recruit" actually than what you would use if you study any other marine organism. A "recruit" to most marine ecologists would be an animal that takes up resided in an ecosystem that its parent lived in residence in some way either attaches or whatever settles to the bottom or something like that. But in fisheries parlance, a "recruit" is an animal that is almost ready to be caught. So what the hell has this animal been doing for the other 4-5 years, right? That’s the question. And there was no answer to that. Until you get a new generation of fisheries biologists who understand that you have to go all the way back the day zero with their biology and know their biology all the way along, the system is not going to change much.
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Les
Watling is a Professor of Oceanography at the Darling Marine
Center, part of the University of Maine.
Can you describe your research with regard to monitoring the
effects of bottom trawls on sea floor ecosystems?