What Science Says About the Sustainability of Trawling

National Fisherman – Guest Author Ray Hilborn – July 21, 2022 •

A Kodiak-based groundfish trawler. Alaska Whitefish Trawlers Association photo.

A Kodiak-based groundfish trawler. Alaska Whitefish Trawlers Association photo.

With the launch of several recent advocacy campaigns, bottom trawling is squarely in the crosshairs of some environmental groups and media outlets that regurgitate their press releases.

There is no question that bottom trawling has environmental impacts, as all food production does, but there is misinformation floating around about the true impact of bottom trawling, especially in comparison to other types of fishing and food production. With campaigns like #BanBottomTrawling growing, I want to look at what the science says about the sustainability of bottom trawling.

Sustainability of target species

Many trawl fisheries are certified by the Marine Stewardship Council and recommended by Seafood Watch. Groundfish populations around the world are largely caught by trawls and are, on average, increasing. Certainly, some stocks like New England cod are in poor shape, but it has nothing to do with the method used to catch them.

Impact of trawling on benthic ecosystems

A defining characteristic of bottom trawling is that it uses nets that are dragged along the seafloor. These nets certainly impact the plants and animals that grow on the bottom, but the overall impact of trawling depends on the sensitivity of the individual species, the kind of fishing gear, the underlying geology of the seafloor, and the frequency of trawls.

Some benthic species such as soft corals and sponges are quite sensitive to bottom trawling because they stick well above the bottom, and they are very slow growing. A few passes of the net may eliminate them completely, and it may be decades before they return.

However, a major paper published last year found that across all regions studied, less than 10 percent of trawled area had lost more than 20 percent of its benthic fauna. The vast majority of trawled areas had lost less than 10 percent of the benthic fauna, and the largest U.S. trawl fisheries in Alaska, only a few percent.

This is a huge win for effective fishery management, but is also explained by the fact that most bottom trawling occurs on sand or mud (not reefs), where the habitat is quick to regenerate and the species that live there are evolved to be resilient to disturbance.

Good management can reduce impacts on benthic ecosystems by closing areas with high density of corals and sponges to bottom trawls, by modifying the fishing nets so that the heavier parts do not touch the bottom, and even by not letting the nets touch the bottom. Many trawlers now use nets that barely touch the bottom.

Bycatch and discards

Almost all fishing gear catches non-target species. If these are not of commercial value they are usually discarded at sea, a waste of fishermen’s time and energy, and a pointless loss of life. Bottom trawling discards and bycatch rates vary greatly, with shrimp fisheries discarding the most, but well-managed bottom trawling can almost totally avoid discards. The bottom trawl fishery in the Bering Sea discards less than 8 percent of its catch.

Bycatch has been reduced or eliminated by modifying net design and ways of fishing, and by sharing information within fishing fleets. In Asia everything caught is retained, and the non-marketable species are used for surimi or aquaculture feed.

Several groups around the world are working on using cameras at the mouth of the net to identify the species and size of fish entering the net, and opening panels that eject the unwanted fish. Discarding is being reduced and nearly eliminated in some fisheries that have made it a priority.

Carbon footprint

The major source of carbon footprint from fishing is from fuel use. One major review showed that bottom trawling was the second highest user of fuel, exceeded only by pot and trap fishing. But there are enormous differences in fuel efficiency depending on the kind of trawl, the age of the vessel, and the abundance of the fished species.

Nearly all trawled fisheries have better carbon footprints than beef. Some have a carbon footprint below chicken and pork and comparable to corn.

Bottom trawling’s carbon impact was all over the news last year when a paper published in 2021 argued that by stirring bottom sediments, bottom trawling released more carbon than air travel. The paper is deeply flawed and has been heavily criticized: other estimates are 100 times lower than the headline-grabbing paper.

The carbon footprint of bottom trawling will continue to decrease as inefficient engine systems are replaced with modern diesel engines and eventually, by hydrogen or electric vessels. Improvements in net and boat design are also improving efficiency. Most importantly, healthy fisheries require less fuel to harvest, so improving stock status is paramount.


Banning bottom trawling is not the right approach to global sustainability. Even the worst impact of bottom trawling on benthic ecosystems is less damaging than agriculture, which completely destroys forests and grasslands to produce food.

Catching fish in the ocean uses no pesticides or fertilizer, no freshwater, no antibiotics, and no land. Bottom trawling produces about one-half as much food as global beef production. If it is banned, where will we make up that food?

The way to sustain food production and minimize the environmental impacts is not to ban trawling, but to manage it by providing incentives to the fishing fleets to minimize bycatch, reduce fuel use, minimize benthic impacts, and protect sensitive habitats.

Ray Hilborn is a professor in School of Aquatic and Fishery Sciences at the University of Washington.

Ray Hilborn, Professor in School of Aquatic & Fishery Sciences at University of Washington

Fishery Council Approves New Restrictions on Bering Sea Trawl Fleet’s Incidental Take of Halibut 

Seattle Times – By Hal Bernton, Seattle Times staff reporter – December 13, 2021 •

A federal fishery council vote Monday could set the stage for future cuts of up to 35% in the incidental halibut take of a largely Washington-based trawl fleet that targets yellowfin sole and other flatfish.

The high-stakes 8-3 vote in an online meeting by the North Pacific Fishery Management Council is likely to result in a big financial hit to this fleet of 19 bottom-trawl vessels. The fleet’s annual $350 million in revenue could be reduced by up to $110 million if halibut stocks are found in surveys to be in very low abundance, according to industry officials.

The council action followed several days of often emotional testimony in an ongoing fisheries battle over the scope of the trawlers’ catch of a revered flatfish — found off the west coast, British Columbia and Alaska — that surveys indicate have largely been in decline during the past 15 years.

In 2019, the bottom-trawl fleet’s incidental take, or bycatch, of halibut tallied nearly 3.1 million pounds as vessels used huge nets to scoop up 635.4 million pounds of yellowfin sole and other flatfish. For the trawl fleet, these halibut are a prohibited species and must be jettisoned overboard.

Some of those trawl fleet’s halibut discards survive. But in 2019, 1.4 million pounds’ worth of halibut did not survive the nets. And over the years, the scope of these discards has angered tribal, sport and commercial fishers who land these fish with hook-and-line gear.

The bottom-trawl fleet’s current cap is a fixed amount that does not vary from year to year. If the fleet reaches that cap, the vessels must stop fishing. The council lowered that cap by 25% in 2015 and the fleet has stayed under the limit. But that action did not quell the movement to further lower trawl discards.

Opposition has flared among halibut fishers in the Northwest and Canada, and has been very intense in Alaska coastal communities.

Halibut fishers have seen their own quotas shrink and have demanded that the trawl fleet’s halibut take also come down. In many Alaska costal communities, halibut is often both an important local food source and also a significant source of revenue when sold for processing and delivery to seafood markets in the United States and elsewhere.

“Halibut bycatch must be reduced immediately,” said Simeon Swetzoff Jr., a former mayor of St. Paul in Alaska’s Pribilof Island and a Bering Sea halibut fisher who has long lobbied to limit the trawl discards.

The nets on this vessel are pulled along the bottom to target flatfish in areas of the Bering Sea where halibut also are found. The halibut brought on board must be thrown back. (Courtesy of Groundfish Forum)

In the Bering Sea region, the amount of halibut last year thrown overboard by the trawl fleet exceeded the amount caught by hook-and-line fishers. In his council testimony, Swetzoff said that the “bolts (on the trawl fleet) need to be tightened. … We have tried everything there is to possibly do.”

Representatives of the bottom-trawl industry say that over the past decade they have made major strides in reducing their bycatch. Those efforts include cooperative efforts to avoid halibut hot spots and deck-sorting to more quickly return halibut to the sea. They are doubtful they can make further reductions to comply with the council action, which could reduce their discard quotas by up to 35% in years when surveys indicate halibut are in very low abundance.

“We are shocked that the council made this decision, and come to this conclusion,” said Chris Woodley, executive director of the Groundfish Forum, which represents the bottom-trawlers known as the “Amendment 80” fleet.

Woodley said that the fleet is a huge provider of frozen fish protein. Much of that fish is exported to Asia but it includes fillets marketed as flounder skinless fillets that can be found in U.S. supermarkets. He said the action will hit hard not only boat owners but also some 2,200 crew who catch and process this fish.

Industry officials say that they would likely have to tie up their boats long before their total flatfish quotas are caught. That could result in this fleet providing up to 200 million less fish meals, according to statement released by the Groundfish Forum.

Woodley noted that an analysis by council staff found that the overall “net benefits to the nation” from this action would be negative. He said no decision has been made by his group about whether to eventually pursue legal action over the council’s action.

The council, with 11 voting members, was formed by congressional legislation and is empowered to come up with harvest rules that are then put into final form by National Oceanic and Atmospheric Administration Fisheries.

The council is composed of fishing industry as well state and federal officials, with Alaskans controlling the biggest share of the voting seats on the council.

Alaska council members who voted in favor of the message were joined by one Washington state council member and a federal representative.

Their leadership to push through was praised by Jeff Kaufman, a vice president of the Central Bering Sea Fishermen’s Association who said it will “better manage the resource.”

Those opposed included Bill Tweit, a Washington state Department of Fish and Wildlife official who questioned whether the surveys that would be used to determine halibut abundance were accurate enough to put this new rule into action.

“No changes to this framework would make this defensible and actually functional,” Tweit said during the council meeting. In his remarks, Tweit also said that the current conservation management is capable of maintaining adequate stocks of spawning halibut.

Hal Bernton: 206-464-2581 or hbernton@seattletimes.com; on Twitter: @hbernton.

Halibut Cuts Threaten the Livelihood of Thousands of Fishermen

Anchorage Daily News Opinions – By Bob Hezel and TJ Durnan – December 10, 2021 •

The factory trawler American Triumph docks in Seward on July 22, 2020. (Loren Holmes / ADN)

We are two captains with a combined experience of more than 70 years in Alaska’s groundfish trawl fisheries.

In that time, we’ve been a part of a trawl fishery that has evolved and innovated heavily to meet several regulatory challenges. This is thanks to a collective commitment of the 2,200 fishermen and women who participate in our fishery. Our families are fishing families, too – as important as any other. We believe we are true stewards of the North Pacific resources. But cuts to our halibut bycatch caps under consideration by the North Pacific Fishery Management Council at its upcoming December meeting threaten our fishery and our way of life.

Our fleet has achieved a 49% reduction in halibut bycatch mortality since Amendment 80 rationalization in 2007. Halibut now represents 0.4% of our catch, which is among Alaska’s lowest bycatch rates, and far lower than Canada’s West Coast fisheries, which are often held up as an example of low bycatch rates. But it has not been easy to get here.

Over the past 10 years, we have designed and developed numerous technologies to lower bycatch in our nets, including halibut excluders and elevated sweeps to reduce bottom contact. These technologies have been implemented with great cost in time, material, and lost productivity of our vessels — not to mention all the frozen hours out on deck for our crews who have willingly helped us to create and refine these devices. While some of these gear modifications showed promise for reducing halibut catches initially, now that halibut are mostly about the same size as our target fish there is no sensible reason to expect that anything more than very marginal gains will come from additional innovation in the field of net and excluder design. This is the industry consensus of captains, net and excluder engineers, and technicians.

We have also worked hard to develop operational methods of reducing halibut bycatch. As a fleet, we’ve developed deck sorting procedures which greatly reduce halibut mortality, returning far more of these fish live to the sea while maintaining accurate observer accounting. We started this work in 2009 with two vessels, expanding and refining the program over many years. This program has been a remarkable success, and it has recently been accepted into regulation by the National Marine Fisheries Service. However, the consensus of captains, scientists and crews is that all the gains from these methods have already been achieved.

While we are always looking for new innovations, we know of no new piece of gear that gets us to a place where we can take another cut. This means that the halibut cuts under consideration for our fleet will force a dramatic contraction in the target harvest. This will have devastating impacts on our fishery and the people who work so hard in it. The council’s own review acknowledges that there are no new tools for us and indicates that an average Amendment 80 crew member stands to lose $24,000 to $48,000 in income annually from the cuts the council is considering. The benefit to a halibut crew member for cuts to our fishery? $500 to $1,000 a person.

The people in western Alaska who provide goods and services also stand to lose a large source of revenue due to the harvest contraction. Unlike many other fisheries, our sector has traditionally operated year-round, and we bring much needed economic opportunity to coastal communities. This year-long stability and revenue is in danger.

Too often, this issue has been framed as a battle between small operators vs. large corporations. We are not large corporations. We are people and this is our job. We are 2,200 crew members who work tirelessly to earn an honest, decent living and support our families. Our crews come from all walks of life, and we have been able to provide a standard of living that many may not have been able to achieve elsewhere.

The council’s proposed cuts might be understandable if there were a proportional gain to another fishery or a conservation benefit, but the council’s own analysis states that cutting our halibut bycatch further will not improve halibut stocks or yield conservation benefits. According to the science, our halibut bycatch is not the cause of declines in the halibut fishery.

So, when the council meets on halibut bycatch in early December, they need to look to their own science and not make cuts that threaten our fishery and provide no benefit to halibut fishermen. Our families are depending on it.

Bob Hezel is captain of C/P America’s Finest and TJ Durnan is captain of C/P Alaska Spirit, two factory trawlers for Fishermen’s Finest and O’Hara Corp., based in the Seattle area. Both boats fish for wild Alaska sole and flounder, Pacific cod, Pacific ocean perch, and Atka mackerel in Alaska’s Bering Sea.

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