Skip to content

From pink nigiri pressed softly atop rice, to buttery seared salmon that melts in the mouth, seafood has long been a culinary pleasure, a lauded source of protein and Omega-3 fatty acids . . . and a problematic indulgence in a world imbalanced by destructive fishing practices, biodiversity loss, and climate change. Fish farms discharge harmful nutrients and antibiotics into the sea and damage wild fish populations. And wild-caught fish comes at a cost, too.

Many of us think of fishermen nostalgically – the last of the hunter gatherers-- testing their mettle in the ocean to catch our dinners. Perhaps we fondly remember trips to small fishing towns along the coast and a comforting meal pulled fresh from the sea. However, lest we get too misty eyed, it’s important to remember that the equivalent practice of market hunting for wildfowl or big ruminants like buffalo or elk began to end in the US in the final decades of the 19th century as wildlife populations plummeted.

The health of the ocean, and the practices behind commercial fishing, have both been changing dangerously for some time. It’s time for our questions to change, too. How can human communities—from developed nations that have the luxury to choose which proteins to eat, to countries where subsistence fishing feeds hungry mouths—secure food in sustainable ways? How can we care for a dangerously over-strained ocean, guided not just by our hearts and habits but by science?

The truth is that while many were surprised to learn of the impacts of fishing on marine life and ocean health in the recent Netflix documentary Seaspiracy, understanding these impacts has been at the forefront of Marine Conservation Institute’s efforts for over 2 decades. Some feel this documentary is unfair to the fishing industry, painting all commercial fishermen, even those who fish with environment friendly gear like pole and line, with the sins of the worst actors like industrial bottom trawlers. Our report “Shifting Gears” was among the first papers to evaluate the environmental impacts of fishing and provides a marine conservation science perspective on Seaspiracy that can help shed light on your seafood choices and help you draw conclusions about whether eating marine life is ok.

In response to the important conversations, misinformation, and awareness that Seaspiracy has brought to the surface, below is a primer on the major impacts of fishing, from a marine conservation perspective.

Bottom Trawling: The Clearcutting of the Sea

The method of bottom trawling began in earnest in the 19th century and intensified in the early 20th century with the advent of engines strong enough to pull rugged nets along the seafloor. Today, some bottom trawlers have nets as wide and as long as a football field, stirring and scraping the ocean floor, scooping up every living thing in their path, and leaving a trail of sediment so large it can sometimes can be seen from space.  Bottom trawls are used in shrimp fisheries and to catch ground fish (fish that like to swim around at the bottom of the ocean). The best estimate of the extent of bottom trawling is that 25% of worldwide industrial catch –about 19 million pounds—is from bottom trawling, which annually scrapes about 14% of the world’s seabed.[i]  This means that every fourth fish is caught by bottom trawl gear. In areas off the west coast (Northern California Current) about 30% of waters are bottom trawled. Three of the top five value fisheries in the US (e.g., pollock, shrimp and cod), worth $3.7 billion in 2018, were caught primarily by bottom trawling.[ii]

Other impacts of bottom trawling include:

  • Bottom disturbance

Scientists have compared bottom trawling to the impact of ploughing farmland.[i] Bottom trawling reduces habitat complexity, productivity, and biodiversity, in particular weakening ecosystems by decimating invertebrates towards the bottom of the food chain.

  • Climate disruption

Bottom trawling disturbs seafloor sediment and releases huge stores of carbon back into the ocean and atmosphere as CO2—as much as 300 tons of CO2 per year for every square mile trawled. The amount of CO2 released this way approaches the emissions from the entire global aviation sector and represents as much CO2 released by most individual countries, excluding the world’s largest economies. [iv]

  • Habitat destruction

Bottom trawling destroys deep-sea sponges, corals, and other organisms whose structure provides spawning grounds, nurseries, food, and shelter from predators. In many cases these vulnerable species won’t regrow for at least decades and might take anywhere from a century to a thousand years to fully recover. This damage is especially notable in diverse and fragile places like seamounts, which Marine Conservation Institute is working to protect.

Tree coral being discarded from bottom trawler.  This coral was likely hundreds of years old, and some deep-sea corals live well over 1,000 years. Photo Credit Greenpeace, New Zealand

Marine Conservation Institute has worked since its founding in 1996 on issues related to fishing, and in particular, on stopping the practice of bottom trawling, the most destructive, widespread form of commercial fishing.[i]  Nearly 25 years ago in 1998, our founder, Dr. Elliott Norse, co-authored one of the most cited papers on the destructiveness of bottom trawling that compared bottom trawling to forest clearcutting. We are a founding member of the Deep Sea Conservation Coalition that first proposed bottom trawling limitations in 2004 and have worked to identify Vulnerable Marine Ecosystems on the high seas in order to limit bottom trawling there. In the US we have identified Essential Fish Habitat and advocated for banning bottom trawling those areas. Today, we are urging the US to protect the California Seamounts, ancient deep volcanoes off the coast of California from fishing and asking the UN to ban trawling on seamounts around the world. Our annual Blue Park awards highlight the best marine protected areas around the world, all of which ban destructive fishing methods like bottom trawling and longlines.

Beyond Bottom Trawling: The Damages and Nuances of Fishing

In many cases, even when fishing is called ‘sustainable’ by fishery experts, their sole focus is on managing a fish population in the ocean and extracting the ‘maximum or optimum yield,’ and other impacts on the marine environment are secondary concerns. While bottom-trawling is by the far the most destructive fishing practice in the United States and globally, all types of commercial fishing have consequences for ocean health. These negative impacts include:

  • Catching fish faster than they can reproduce leads to smaller and smaller populations. This comes from overfishing and occurs around the world. The Food and Agriculture Organization estimates that approximately 35% of all commercial fish populations are overfished.[vi]  Reconstructed global catch of fish peaked in 1996 at 130 million tons/year; and despite rapidly increasing numbers of fishing boats, catch has declined for the last 25 years by about 1.2 million tons/year.[vii] When more boats are catching fewer fish, that is a danger sign that populations are shrinking despite FAO estimates.
  • Bycatch destroys vulnerable wildlife. Often other species are caught alongside a  target species—this is called bycatch, and the “accidental” catch is often discarded, dead or dying, back into the ocean. The best global estimate is that “industrial fisheries that rely on bottom trawling to catch fish threw 437 million tons of fish and $560 billion overboard over the past 65 years.”[viii]  BBecause many fishing gears are fairly indiscriminate about what gets hooked on longlines or captured in huge nets, marine mammals, sea birds, sea turtles and non-target fish, including sharks, have plummeting populations due to bycatch. For example, for every pound of wild shrimp caught by shrimp trawlers in the Gulf of Mexico, about 5-10 pounds of other marine life is discarded as bycatch. Some studies estimated that 90% of the mortality of red snapper in the Gulf of Mexico between ages 0-1 year (in other words, young fish that would otherwise grow up to increase populations for other fishermen or feed other species) was caused by shrimp trawling.[ix]
  • Fishing limits reproductive success. Fishing tends to catch bigger, older, more mature fish than the general population of any species, thus driving the population towards younger, smaller, less reproductively successful members. In many species, the so-called “Big, Old, Fat Females” produce orders of magnitude more eggs and larvae than younger females. Thus they are capable of sustaining populations in fluctuating ocean conditions better.
  • Targeting big bodied species can lead to ecosystem collapse. Because industrial fishing selectively targets more commercially valuable species which tend to be large-bodied predators (e.g., tuna, sharks, snappers, groupers) or large bodied grazers (e.g., parrot fishes), the underlying populations of other fish that are controlled by top predators ‘get out of whack’, sometimes causing a negative cascade of impacts on the rest of the ecosystem.


Taking Action for the Sea

Conversations around Seaspiracy have pushed people to double down on strong opinions about seafood and fishing. The reality is that competing pressures from biodiversity loss, human population growth, habitat destruction and climate change make easy answers challenging. Below are some of the simplest, strongest actions each of us can take to mitigate the damages from commercial fishing and to champion a healthier ocean for all the life that depends on it . . . including ourselves and future generations.

  • Support effectively managed marine protected areas (MPAs). Scientists agree that one of the most powerful tools to rebuild biodiversity and support marine resilience is to safeguard areas of the ocean from human damage and exploitation. Not all MPAs are alike, and many of them still allow for destructive fishing practices along with other resource extraction. The Biden Administration recently committed to protecting 30% of land and sea by 2030, and many other global leaders are pushing toward this goal, as well. But the quality of those protected areas matters as much as the quantity. A growing body of evidence shows that specific characteristics are necessary for an MPA to have real and lasting conservation benefits, including “no-take” areas where fishing is banned. Learn more about those science-informed criteria by exploring our Blue Parks initiative, and track the places in the ocean that are leading or lagging in conservation effectiveness by visiting the Marine Protection Atlas.
  • Skip fish altogether, or limit fish in your diet, and make consumer choices that don’t support bottom-trawling. Whether you decide to eat marine life or not, your choices have environmental impacts. Not all nations or people have the luxury to choose which protein to eat. Many people in developing countries rely on fish for subsistence or a livelihood. However, in the U.S., marine life from bottom trawling is widely available at your supermarket and fish store. If you want to avoid it, here are some of the kinds of fish and shellfish you might want to avoid:
    • Pollock – made into fish sticks, fish sandwiches at fast food stores and surimi
    • Shrimp
    • Cod or scrod
    • Scallops and clams
    • Bottom fish like flounder, skate, sole, haddock, western rockfishes, etc.
  • Support marine conservation work informed by science. For over 25 years, Marine Conservation Institute has fought bottom-trawling and worked urgently and strategically to safeguard wild ocean places. With your support, we can continue to build toward a healthy future for this blue planet.

[i] For a summary of this study by the fisheries dept at UW see:

[ii]  NOAA, Fisheries of the United States, 2018 pg. xvi

[iii] Ploughing the deep sea floor

Nature volume 489, pages286–289(2012) Cite this article.

[iv] Sala, Enric; Mayorga, Juan; Bradley, Darcy; Cabral, Reniel B.; Atwood, Trisha B.; Auber, Arnaud; Cheung, William; Costello, Christopher; Ferretti, Francesco; Friedlander, Alan M.; Gaines, Steven D. (2021-03-17). "Protecting the global ocean for biodiversity, food and climate". Nature: 1–6. doi:10.1038/s41586-021-03371-z.



[vii] Daniel Pauly and Dirk Zeller, eds. Global Atlas of Marine Fisheries; A Critical Appraisal of Catches and Ecosystem Impacts. Island Press. 2016, page 173.