Given the extensive damage it does to the seafloor, bottom-trawling for shrimp can be likened to felling forests to catch squirrels. Quite valuable squirrels, to be sure: Experts calculate that in 2022, global shrimp sales generated US$30-35 billion.

“The international shrimp industry is highly destructive and driven by an insatiable market,” says Max Bello, international ocean policy director at Mission Blue, an international marine conservation nonprofit headquartered in San Francisco, California.

For years the leading locus of that insatiability was the United States. But the U.N. Food and Agriculture Organization reports that last year China displaced the United States as the world’s top shrimp import market, with most of its supply coming from Ecuador. The demand has been met in part by shrimp-farming operations, which account for about 55% of world shrimp production, experts say, and these have been associated with their own set of environmental ills—most notably, extensive coastal mangrove destruction. (See Q&A—this issue.)

But when it comes to ocean-caught shrimp, it’s the bottom-trawling operations that have generated the most criticism. Experts say shrimp fishers have focused on expanding production and profits, paying little attention to the environmental effects of their equipment and practices.

In the Caribbean, Gulf of Mexico, and Eastern Tropical Pacific, these nets indiscriminately scour the ocean floor, destroying benthic habitat that is home to thousands of marine species. “The impact of bottom-trawling to catch shrimp is enormous because over 90% of what the nets collect is incidental catch,” Bello says. “All plant and animal species ranging from sharks, turtles, fish, crustaceans, corals and seaweed are hauled out indiscriminately, only to be discarded later, dead or dying.”

Although bottom-trawling accounts for only an estimated 5% of the commercial shrimp supply, it is believed to produce dramatically disproportionate environmental damage due to its impact on seafloor habitats.

Shrimp species can be found in freshwater and saltwater environments. In the ocean, where roughly three-quarters of shrimp species live, they inhabit waters ranging from the poles to the tropics and from shallows to depths of up to 5,000 meters (16,000 feet).

As overfishing in near-shore waters has occurred in many countries, bottom trawlers and those using other types of shrimp nets have had to fish in progressively deeper waters. In the case of bottom trawling, that has meant a growing toll of seafloor damage.

Multiple impacts

That damage includes netting and killing multiple non-shrimp species, some endangered; disrupting seabed morphology; stirring up sediments, which worsens water quality and blots out sunlight; and taxing the undersea environment as vessels dump enormous volumes of dead bycatch. Scientists say large quantities of CO2 are released when bottom-trawls rake the seabed—up to 370 million metric tons annually, according to research published recently in the journal Frontiers in Marine Science.

In 2010, Belize became one of the first countries in the world to outlaw all bottom-trawling in its waters. The restriction, still in effect, has coincided with a rebound in populations of shrimp and other marine life, local communities report. Pushback against bottom-trawling has spread to other countries in the region, including leading regional shrimp-producers Panama, Colombia and Ecuador, where ocean-protection advocates are beginning to advance proposals to limit the practice.

In Costa Rica, concerns about seafloor damage prompted lawmakers to outlaw bottom trawling in 2013, when shrimp caught by that method in the country’s Caribbean and Pacific waters exceeded 750 tons annually. But in Sept. 2022, President Rodrigo Chaves announced a study to gauge whether new net designs could make bottom trawling environmentally sustainable enough to lift the ban. The move alarmed advocacy groups such as the MarViva Foundation, a nonprofit that promotes responsible management of marine resources in the Eastern Tropical Pacific. MarViva demanded access to the study’s methodology and to background on stakeholders involved in the exercise. The government did not respond to the request until January 2023, after a court ordered the Costa Rican Fishing and Aquaculture Institute (Incopesca) to share the information.

Trawling study challenged

Drawing on that information, MarViva contended the design of the study was faulty. It asserted that the research, which would involve years of bottom trawling, could cause irreparable damage and would not adequately address key environmental and social impact questions. MarViva challenged the study in court, winning an injunction pending resolution of the case.

“We cannot allow the authorities to spend public funds on research that has no technical or scientific foundation and lacks a socio-economic analysis,” says environmental attorney Katherine Arroyo, executive director of MarViva Costa Rica. “Authorities should do thorough studies on the real state of affairs to define sustainable management plans so resources are responsibly exploited. We cannot allow policies that further deplete or endanger marine stocks.”

Underlying such criticism is concern that fishing authorities are unduly influenced by private fishing interests, a problem they fear will prevent proper impact and cost-benefit analysis. Says Arroyo: “Costa Rica’s environmental standards are slipping with the centralization of decision-making into the hands of a few.”

Costa Rica is one of many nations that subsidize shrimp fishing. Critics say this artificial support masks longstanding evidence that shrimp fishing is not viable from a cost-benefit perspective and that other species such as tuna, if adequately managed, could bring far more socioeconomic benefit with less damage.

“We are not generating social mobility but rather perpetuating undignified jobs that do not reduce social inequalities or conserve marine habitat,” Arroyo says. “By sticking to these outdated and destructive ideas we are continuing to damage the planet and preventing the introduction of models of sustainability that we urgently need to meet [world biodiversity conservation] goals. Fishing subsidies are an issue the world over, as they sustain unsustainable practices.”