Seven ways fishing trawlers aren’t great for the seabed

I’m writing this in the high Arctic at 78º North Latitude in early July, aboard Greenpeace’s Arctic Sunrise where I’m a guest for a few days, with 24-hour daylight and gleaming glaciers in the valleys of snow-capped coastal mountains. We’re here because shrinking sea ice and warming ocean water is moving fish farther north, and fishing vessels are coming with them.

These are big trawling ships, and in other regions trawl-fishing has harmed—in some cases ruined—vast areas of seafloor. Here there’s still a chance to get it right by letting trawlers work in some areas and designating other areas as trawl-free zones. We’re here to document the trawling and help advance the discussion.

Trawling ship. Credit: Carl Safina
Trawling ship. Credit: Carl Safina

Trawling at its most basic it’s a boat pulling a net through the water. Sometimes that net is midway between surface and seafloor. Sometimes—most of the time, actually—it’s dragged across the seafloor. Trawls have been called “bulldozers of the ocean.”

Recently some big retailers like McDonald’s and the major fishing companies of Norway and Russia have entered into an agreement with Greenpeace to not expand further until an agreement can be reached to put some big areas here aside, safe from trawling.

Trawling is one of the most basic and most effective ways of catching sea life. That’s good if you’re trying to catch sea life. If you’ve eaten fish, most were probably caught by trawling. Some of the most familiar fish like cod and flounder are caught mostly by trawling. Calamari?—trawling, mostly. Had a fish sandwich at a fast-food mega-franchise?—trawling. So if you’re in the fishing biz or enjoy your Fish-wich, trawling’s been part of your life. And not just seafood; the feed fed to farmed animals including farmed fish usually contains a lot of trawler-caught fish-meal. So most chickens and pigs and farmed salmon and shrimp are raised partly on ocean fish caught by trawling.

Here are some major issues:

  1. Overfishing. Millions of tons of sea life find themselves engulfed in trawl nets each year. Trawling has been done so intensively that it’s depleted many kinds of fish in many parts of the world. Catches must be strictly managed or in a few years there’ll be little left.
  1. Untargeted, unwanted catch, or “bycatch.” Regardless of different variations in method, the one thing all trawlers have in common is that they basically core a hole through the ocean, so they catch a lot of things they’re not trying to catch—unmarketable fish, marine mammals, even seabirds. In some fisheries the catch is pretty “clean.” But in many, more than half of what trawls catch is unwanted. Virtually all of a trawl’s catch comes up dead or fatally injured, and if it’s unwanted it’s just shoveled back. Shrimp fishing can be some of the worst, because small mesh also catches small fish. And large fish. At times, they can catch 10 fish for each single shrimp. Many are babies of large species, and have no market. Out come the shovels. I’ve seen it many times.
  1. Destabilization of the seafloor. If the net is dragged, it is weighted. It plows heavily along the seafloor. Most of the deeper ocean seafloor has extremely stable natural conditions. Stable currents, stable temperature (it’s cold; things grow slowly). Not much happens to disturb the peace. Enter: disturbance—trawlers.
Heavy plates used to weight drag nets. Credit: Carl Safina
Heavy plates used to weight drag nets. Credit: Carl Safina
  1. Corals. Corals aren’t just for tropical reefs. Many coral species have specialized to grow in deep, cold water. Those corals often continue growing for centuries (I’ve read that they can be thousands of years old)—until the moment a trawl snaps and crushes them. Off Florida and New Zealand, deep corals have been 97-99 percent destroyed by trawling (Allsopp et al. State of the World’s Oceans, 2009, Springer). This is where fish live and hide; it’s their habitat. These deep reefs and coral groves are among the oldest old-growth on Earth. And there are many kinds of soft corals too. That word “soft” can help you guess what happens when a heavy trawl net comes plowing through.
  1. Anemones, sponges, sea pens, urchins, and other fine, fragile-bodied animals. A lot of the seafloor harbors delicate upstanding creatures. Woe unto them; they shall be felled.
  1. Within the seafloor. Trillions of shelled or soft-bodied animals like worms, amphipods, clams, crabs, lobsters, and many others live in the seafloor in their quiet burrows, minding their own business and hiding. Quite crushable. This fauna is also food for fish and crabs. So even if you don’t care, even if you just want to catch or eat fish—if your method of catching fish kills the food of fish and ruins the places where fish live and hide, there won’t be as many fish to catch. In that sense, trawling can be like sawing off the tree-limb you’re standing on. So where trawlers trawl and what trawlers do makes a big difference to our ocean and our food supply. That’s why we need trawling-free areas.
  1. Justice for all. Shocking perhaps, but the world wasn’t made just for those of us who happen to be here right now. The world was here and doing just fine for millions of years before we showed up. These trawling ships have been around for just a few decades. There are many people alive who were alive when the first big trawlers went to sea. And there will be many people alive in the future who will get what we leave and won’t get what we ruin. We can take care of the place, or we can wreck it. It’s really a deeply moral consideration. But there’s nothing that says the world owes us all the fish in the sea. Leaving some space in the sea is the smart—and the decent—thing to do.
Fragile seafloor of Svalbard. Credit: Carl Safina
Fragile seafloor of Svalbard. Credit: Carl Safina

#   #   #

Carl Safina’s recent bestselling book Beyond Words; What Animals Think and Feel is newly out in paperback. See Carl’s TED talk here. He is Stony Brook University’s Endowed Professor for Nature and Humanity, and founder of The Safina Center.



Ecologist Carl Safina is author of seven books, including the best-selling “Beyond Words; What Animals Think and Feel,” and “Song for the Blue Ocean,” which was a New York Times Notable Book of the Year. His writing has won a MacArthur “genius” prize; Pew and Guggenheim Fellowships; book awards from Lannan, Orion, and the National Academies; and the John Burroughs, James Beard, and George Rabb medals. His work has been featured in The New York Times, The Los Angeles Times, The Washington Post, National Geographic, CNN.com and elsewhere, and he hosted the 10-part “Saving the Ocean” on PBS. Safina is founding president of The Safina Center at Stony Brook University.
  • Clifford Goudey

    Carl, you write, “We’re here to document the trawling and help advance the discussion.” Gee, it doesn’t sound that way. It sounds like you are on a mission to ban trawling.

    Overfishing is caused by poor management or inadequate enforcement and is independent of the methods used by fishermen. Trawl nets have two particularly useful features: 1) they catch fish in proportion to their abundance and 2) the mesh size of the net determines the size of the smallest fish that is caught. Bycatch is an artifact of a poor management scheme. Throwing back dead fish is wrong on so many counts but is largely dictated by regulations. Even the most “worthless” critter landed on deck can produce value if landed instead of being shoveled overboard to feed birds or other scavengers. The entire 1st-world seafood value chain it set up to exaggerate this wasteful paradigm that dictates what is marketable and what is trash. Small mesh fisheries such as shrimping need to retool with other methods that can demonstrate a proper targeting of the resource. That may mean the abandonment of present practices.

    A trawl net can seem heavy when sitting on deck but once deployed and pulled through the water, it needs weight to even reach the bottom. Proper nets are designed to provide uniform but light contact with the seabed. Anything more means damage to the net and more towing resistance. Only those unfamiliar with their operation or heavy with an anti-trawling agenda equate the method to bulldozing.

    As you have suggested, most of the fish we eat are caught by trawling and the very durability of those fisheries should give you pause when you suggest a trawl net “ruins the places where fish live and hide.” Most trawling takes place on well-established tows that are free of obstacles and offer a history of being productive. The location of these tows are handed down through the generations and shared only carefully because of their cherished value. You suggest one pass of the net ruins everything and this wrong. It is also why so-called data on the percent of the bottom impacted by trawls simply doesn’t compute. That effort is focused repeatedly on proven tows and exploratory fishing outside of these tows is considered by most as an expensive adventure.

    The popular trend to close vast areas of the ocean to fishing is counterproductive. Most of the oceans are already protected from trawling by being too deep, unproductive, or protected by obstacles that tend to ruin a trawl net. You would do well to look to the real threats to the ocean such pollution, acidification, warming and loss of coastal habitat.

  • Warren Crutcher

    Thank you for the great rebuttal. You articulated the arguments better than I could have. There is far too much misinformation about commercial fishing, and especially bottom trawling. Too bad your response isn’t the actual article….I don’t have any kind words for Greenpeace…so I will sign off.

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (dbraun@ngs.org)

Social Media