Seafood is an excellent source of protein that contains a range of nutrients, most notably the omega-3 fatty acids, EPA and DHA.  Experts recommend eating about 8 ounces per week of a variety of different seafood since the consumption of fish contributes to the prevention of heart disease.  Smaller amounts of seafood are recommended for young children. 

In the US, 80% of fish and seafood for human consumption is imported, but with limited supplies, illegal fishing is rampant.  International fishing management agencies report that at least a quarter of the world's catch is illegal, unreported, or unregulated.  Modern catch methods including trawls and dredges are not only removing fish faster than fish can reproduce, they also destroy delicate habitats that provide shelter, food, and breeding grounds for most ocean species.  According to Seafood Watch, heavily trawled areas are the equivalent of clear-cutting a forest.  What's more, many fisheries throw away more fish than they keep, especially shrimp fisheries, due to fishing methods using longlines or bottom trawls.  These methods produce "bycatch", the incidental catch of unwanted or unsellable species including turtles, seabirds, and other seagoing animals. 

Contaminants in Fish

Most seafood varieties contain different levels of methyl mercury.  Mercury itself is a naturally occurring element that is present throughout the environment and in plants and animals. But human industrial activity (such as coal-fired electricity generation, smelting, and the incineration of waste) ratchets up the amount of airborne mercury which eventually finds its way into lakes, rivers, and the ocean, where it is gobbled up by unsuspecting fish and other marine life.  Once this mercury gets into the marine food chain, it “bio-accumulates” in the larger predatory fish.   That’s why larger fish are generally riskier to eat than smaller ones.   Mercury can be toxic to the human brain, kidney, liver, heart, and nervous system. Research has shown that people who eat a lot of high-mercury fish frequently can experience nervous system damage and can suffer from a variety of ailments, including sleep disturbance, headache, fatigue, difficulty with memory and concentration, poor coordination, and neuropathy.  Mercury is much more dangerous to a developing fetus. Mercury exposure during pregnancy can cause lasting deficits in the development of a child’s brain and nervous system.  Studies of children exposed to high levels of mercury in the womb indicate that they score lower than other children on intelligence tests and perform poorly on tests of memory, attention, and hyperactivity.

Why This Matters:

Consuming large quantities of contaminated fish can have negative long term consequences, especially in children, pregnant and nursing women, and the elderly.

PCBs, a large group of related industrial chemicals, are also common contaminants in fish in many parts of the world.  PCBs are man-made pollutants produced in the United States from about 1930 to 1977.  They were used in electrical transformers, plastics, and lubricating oils.  PCBs have been banned since then for most uses because they do not break down easily and stay in the environment for a long time.  Spills, leaks, and improper disposal are the main ways that PCBs have entered the environment.  When PCBs are consumed by fish, they are stored mainly in the liver and the fat.  OEHHA (Office of Environmental Health Hazard Assessment in California) recommends that fish be cleaned, gutted, and cooked before it is consumed to reduce the amount of PCBs, and not to use any of the remaining fish for other dishes, especially the fat, skin and juices. 

Dioxins are highly toxic, cancer-causing compounds produced as byproducts of herbicide production and paper bleaching.  It is a serious and persistent environmental pollutant that breaks down very, very slowly and can be concentrated in fish and shellfish which can have much higher levels than the plants, water, soil or sediments around them. 

Ocean (and Human!) Friendly Fish

Seafood varieties that are commonly consumed in the United States that are higher in EPA and DHA and lower in mercury include:

Farmed Mussels & Oysters

Farmed Arctic Char

Farmed Tilapia

Salmon including Wild Alaskan, Coho, Sockeye (Red Salmon), Chum (Keta Salmon), and King

Pacific & Atlantic Mackerel (not King Mackerel, which is high in mercury)

Pacific Sardines

Farmed Rainbow Trout

Pollock (Imitation Crab)


At the other end of the spectrum are fish at risk for higher levels of contaminants and lower levels of beneficial omega’s:

Atlantic Tilefish



Flatfish (Plaice, Sole, Flounder)


Haddock & Hake

Mahi Mahi



Ocean and Freshwater Perch







Crab, including Blue and Dungeness

Pacific Cod

Black & Striped Seabass

Tuna – including canned Albacore, tuna steaks and sushi, Skipjack, and Yellowfin

Some fish are avoided altogether due to their high level of contaminants and their poor sustainability track record:

Orange Roughy



King Mackerel

Gulf Tile Fish

Wild, freshwater Trout


Seatrout (Weakfish)

Chilean Seabass


Spanish Mackerel

Albacore Tuna Steaks,

Striped & Blue Marlin


Big Eye Tuna & Bluefin Tuna




More About Tuna

Americans eat about 2.6 pounds of canned tuna per person per year, making canned tuna the second favorite seafood after shrimp.   About 70% of canned tuna is bigeye, skipjack, and a small number of yellowfin species, typically canned as "light" tuna.   Albacore, canned as "white" tuna, represents about 30% of the tuna consumed in the US.   All the tuna consumed in the US is wild-caught.

Stocks of skipjack tuna – the source of 60% of the global annual tuna catch – are considered by scientists and industry experts to be strong and sustainably fished worldwide.   Bluefin tuna – the focus of vigorous conservation efforts – is not used in commercial canned and pouched tuna products.   America’s tuna companies actively participate in bluefin conservation initiatives.

As noted earlier, tuna contains varying levels of mercury.   But these levels vary widely by type of fish and location of catch.  The highest levels of mercury were found in two species, bigeye and lean bluefin (bluefin akami), and the lowest levels were in yellowfin and fatty bluefin (bluefin toro).   Albacore tuna is one of the healthiest fish you can eat, provided it's caught in the U.S. or British Columbia. This type of tuna is caught when it's younger and therefore has had less time to build up high levels of mercury.  Albacore imported from other countries, however, is caught when it's older and thus contains more mercury. Canned albacore is always labeled "chunk white."   Since the U.S. requires that all fish and seafood be labeled with its country of origin and method of production (e.g. wild or farmed), consumers may make an educated choice by reading canned tuna labels for source information.

"Chunk light" tuna is a blend of different species and often includes meat from high-mercury bigeye tuna, along with less-contaminated yellowfin.  "Chunk light" and "canned light" aren't the same thing, either. The most common type of tuna sold as "canned light" is skipjack, which is sometimes referred to as yellowfin, and contains relatively low levels of mercury. These types of tuna, when consumed in large amounts can be harmful to women and children, so experts frequently recommend that consumers look for and purchase chunk white albacore tuna from U.S. and British Columbia fisheries.

A large majority of the Albacore tuna caught for commercial purposes comes from the Pacific Ocean.  In this area, dolphins and tuna are known to swim together in closely packed schools.   For decades fishermen normally looked for dolphin schools, knowing that they’ll find tuna swimming underneath them.  Then they would set a purse seine (a huge net) that would encircle the school of tuna and dolphins.   Finally, in 1990, the Dolphin Protection Consumer Information Act was passed which requires that tuna may be labeled as dolphin-free or dolphin-safe provided that "no tuna were caught on the trip in which such tuna were harvested using a purse seine net intentionally deployed on or to encircle dolphins, and that no dolphins were killed or seriously injured in the sets in which the tuna were caught.”

Why This Matters:

Consumers want to be ensured that they are purchasing tuna that is caught by methods that do not harm dolphins and do protect the marine ecosystem.

Today, consumers can find the Dolphin Safe seal which guarantees that Dolphins were not the bycatch of the tuna harvested for that producer.  Producers must abide by the following criteria in order to display the seal:

  1. No intentional chasing, netting, or encirclement of dolphins during an entire tuna fishing trip
  2. No use of drift gill nets to catch tuna
  3. No accidental killing or serious injury to any dolphins during net sets
  4. No mixing of dolphin-safe and dolphin-deadly tuna in individual boat wells (for accidental kill of dolphins), or in processing or storage facilities
  5. Each trip in the Eastern Tropical Pacific Ocean (ETP) by vessels 400 gross tons and above must have an independent observer on board attesting to the compliance with points (1) through (4) above
Dolphin Safe Seal

There are several logos that designate tuna as dolphin-safe. The most highly regarded is the program administered by Earth Island Institute.  Under this program, the Institute monitors tuna companies around the world to ensure the tuna is caught by methods that do not harm dolphins and protect the marine ecosystem.  Their standards are adhered to by more than 90% of the world’s tuna companies.

Responsibly Farmed Fish (Aquaculture)

Aquaculture refers to the breeding, rearing, and harvesting of plants and animals in all types of water environments including ponds, rivers, lakes, and the ocean.  Researchers and aquaculture producers are "farming" all kinds of freshwater and marine species of fish, shellfish, and plants.  Aquaculture produces food fish, sport fish, baitfish, ornamental fish, crustaceans, mollusks, algae, sea vegetables, and fish eggs.

Why This Matters:

There are many different methods used in farming fish ranging from poor to superior. Water conditions, quality of the feed, the density of the pens, and a few of the differentiating qualities of aquaculture.  As a result, a fish labeled “farm-raised” does not necessarily indicate mean good or bad quality.  Store staff members should obtain additional information about the source of the fish and the methods used for raising, harvesting, and handling fish sold in the store.

Marine aquaculture refers to the culturing of species that live in the ocean.  U.S. marine aquaculture primarily produces oysters, clams, mussels, shrimp, and salmon as well as lesser amounts of cod, Moi, yellowtail, barramundi, seabass, and seabream.  Marine aquaculture can take place in the ocean (in cages, on the seafloor or suspended in the water as a column) or in on-land, manmade systems such as ponds or tanks.  Recirculating aquaculture systems that reduce, reuse, and recycle water and waste can support some marine species.

Freshwater aquaculture produces species that are native to rivers, lakes, and streams.  U.S. freshwater aquaculture is dominated by catfish but also produces trout, tilapia, and bass.  Freshwater aquaculture takes place primarily in ponds and in on-land, manmade systems such as recirculating aquaculture systems.

Fish farming is a way to meet the demands for fish in the food supply without further depleting the populations of wild fish in our oceans and watersheds.  In the US, 80% of fish and seafood for human consumption are imported and about half of that is farmed.  Across the world, 210 species are cultivated through aquaculture.   In the US, 19 species are farmed including Salmon, Shrimp, Rainbow Trout, Talapia, Arctic Char, and Catfish.

Fortunately, most farmed fish are low in mercury.   Farmed fish live for a relatively short time so they do not accumulate as much mercury as some species of wild fish.  And if the farmed fish are fed fish meal, it usually is derived from types that are low in mercury. 

Fish & Seafood Labeling

There is no universal seafood labeling system for grocery stores, restaurants, or fish markets.  Only the country-of-origin labeling laws, in place since 2005, requires that retailers selling fresh or frozen fish indicate the country the fish came from and whether it is wild-caught or farm-raised.

While eco-labels for seafood are more prevalent in Europe than the U.S., the main one to watch for is the Marine Stewardship Council (MSC). The MSC is the largest and most globally recognized eco-label for wild-caught seafood. Its standards meet the United Nations’ eco-labeling guidelines, and to date, the MSC has certified almost 200 fisheries (with a similar amount undergoing assessment). To obtain the MSC seal of approval, a fishery must demonstrate effective management, and maintain healthy populations and ecosystems.

The U.S. Department of Agriculture (USDA) has yet to finalize organic standards for farmed fish in the United States, but “organic” salmon, shrimp, cod, and tilapia from abroad are still available.  While these labels provide some information about the quality of the fish, they do not necessarily translate into environmental sustainability.  For example:

  • Most foreign organic standards allow the use of open-net pens that can pollute surrounding waters.
  • Several certifiers permit the use of chemicals to control parasites.
  • Some allow nonorganic seafood byproducts, which may have significant levels of contaminants, in fish feed.

It is more difficult to determine an organic standard for fish than for produce and livestock.   Fish that are vegetarian may require different standards than carnivorous fish, as will bottom feeders.   Also, environmentalists believe that because farm-raised fish tend to live in cramped conditions more water pollution may occur. This may cause the fish to be unsustainable and unhealthy, so calling them organic misrepresents the product.   Currently, adherents of strict application of organic agricultural standards to aquaculture hold that the principles of organic aquaculture must include:

  • Careful selection of sites for aquaculture farms
  • Protection of adjacent ecosystems
  • Active avoidance of conflicts with other users of the aquatic resources (e.g., fishermen)
  • Prohibition of chemicals (e.g.. as anti-fouling agents in net pens)
  • Natural remedies and treatments in the case of disease
  • Feedstuff from organic agriculture
  • Fishmeal and -oil in feed derived from by-products of fish processed for human consumption (no dedicated "feed fishery")
  • Prohibition of GMOs, neither in feedstuff nor in the stock itself
  • Processing according to organic standards

In 2008, the NOSB voted to accept recommendations for organic aquaculture, but the result was controversial and as a result, no further action has been taken by the NOP.  In the meantime, California currently prohibits sales of "organically" labeled fish until U.S. standards are in place.

Safe Fish Handling

Seafood is more perishable than many food items so more attention must be paid to its careful handling and storage.  Spoilage is a complex process caused by enzymes present in the fish and by microbes that invade the fish after death.  Microorganisms can come from the marine environment, water pollution, or contamination caused by improper handling.   These microbes increase the rate of spoilage and some can cause illnesses such as the human enteric viruses, listeria, and salmonella, among others.

In general, the basic rules are:

Keep it cold – Fish should be refrigerated or frozen.  If refrigerated, it should be kept as close to 32°F as possible to prevent the growth of microbial pathogens and prevent toxin formation.

Keep it clean – Fish must be handled and prepared in a clean area to avoid cross-contamination, including hands, preparation area, and utensils.   Never let raw seafood come in contact with already cooked or ready-to-eat foods (e.g. salads, fruit, smoked fish).   Whether storing fresh fish or thawing frozen fish, make sure that the juices from raw seafood do not drip onto food that has already been cooked or food that will not be cooked.

Prepare and cook it properly – Proper cooking is the most effective way to ensure that bacteria, viruses, and/or parasites that could be present in seafood are eliminated or controlled.   But even proper cooking may not maintain seafood safely if the fish has not to be maintained at proper temperature beforehand.  Improper handling can lead to the formation of heat-stable microbial toxins or biogenic amines that cannot be removed with cooking. 

Individuals with underlying gastrointestinal disorders or fish allergies, the young, the elderly, individuals with compromised immune systems, and females that are pregnant or nursing should be advised against eating raw or undercooked seafood products like raw fish or shellfish, cold-smoked seafood, and ceviche.


Words to Remember


ALA, an essential fatty acid (EFA), is a shorter-chain omega-3 that serves as a source of energy and as a building block for long-chain omega-3 fatty acids (DHA and EPA).



Refers to the breeding, rearing, and harvesting of plants and animals in all types of water environments.



An increase in the concentration of a chemical (such as mercury) in a biological organism over time as compared to the chemical's concentration in the environment. Chemical compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.



The definition of bycatch used by the NOAA (National Oceanic & Atmospheric Administration) Fisheries is "Discarded catch of any living marine resource, plus unobserved mortality due to a direct encounter with fishing gear."



An omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, sperm, testicles, and retina. It can be synthesized from alpha-linolenic acid or obtained directly from certain foods including some meats and fish.



Are highly toxic compounds produced as a byproduct in some manufacturing processes, notably herbicide production and paper bleaching. It is a serious and persistent environmental pollutant.



When used on canned tuna labels, this means that the tuna in the can has been harvested using fishing methods that are not harmful to dolphins.



EPA is a long-chain omega-3 fatty acid important for overall health. However, unlike DHA, the body does not store EPA in significant quantities in the brain or retina (DHA is found in every cell throughout the body, EPA is not).



This means a fish that has been caught with a rod and fishing line, not by trawling with a net.



Longline fishing is a commercial fishing method that uses fishing lines up to 15 miles long that carry thousands of secondary lines & hooks baited with whatever fish is at hand meant to target shark, swordfish, and tuna. This method of fishing produces "bycatch" of turtles, seabirds, sharks, and other sea creatures that are not targeted but take the bait anyway.



A natural, organic element found in rocks, coal, and soil. It is also released into the air when soil and rocks decay or volcanoes erupt, or when burning coal and mining gold. Mercury that is in the air returns to earth from rain and snow that runs off into the rivers, lakes, streams, and oceans. Mercury is accumulated in fish from the consumption of tiny plants and animals living in the water. When big fish eat the small fish, the levels of mercury build-up.



PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons that were domestically manufactured from 1929 until 1979 when they were banned. PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; in pigments, dyes, and carbonless copy paper; and many other industrial applications and have a range of toxicity to the environment.



Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net that is used for trawling is called a trawl. The boats that are used for trawling are called trawlers or draggers. Among all the fishing methods, bottom trawling is the most destructive to Earth's oceans.



A fish or animal taken from the wild rather than bred from captive stock.