Although the benefits of eating more fish and other seafood generally outweigh any risks, you should keep in mind some important environmental and health cautions.
First is the fact that if everybody on the planet ate the recommended amount of fish, the world’s oceans, rivers, and lakes would quickly be depleted. Already, according to the United Nations Food and Agriculture Organization, 90 percent of the world’s fisheries are fully exploited or facing collapse. Only the expansion of fish farming (aquaculture) over the past 50 years has enabled the global supply of fish for human consumption to outpace population growth.
If you’re concerned about sustainability, you can do your part by consulting guides to “green” seafood shopping like these:
- Monterey Bay Aquarium Seafood Watch
- Vancouver Aquarium Ocean Wise program
- Environmental Defense Fund Seafood Selector
- Environmental Working Group Seafood Calculator
- National Oceanic and Atmospheric Administration Fish Watch
Both aquarium programs also have apps for your smartphone. Keep in mind that these sources may disagree about the most sustainable choices, given their different priorities. Most of these sites also contain advice about avoiding environmental contaminants. Some organizations, such as the Monterey Bay Aquarium, take both sustainability and health into consideration in their guides.
Farmed fish and the environment
Fish farms, when not properly managed, are infamous for adverse effects on the environment, which include the polluting of water and the spread of disease to wild fish when farmed fish escape their pens. Overseas farms tend to have a bad reputation, though new regulations and certification programs may slowly be changing that. A growing number of fish farms are getting third-party certification from such organizations as the Global Aquaculture Alliance (GAA), Aquaculture Stewardship Council (ASC), and Naturland. Certified farms must meet standards that take into account environmental and community issues, animal welfare, food safety, and traceability, among other factors.
Many major retailers in the U.S. sell certified seafood. For example, more than 150 retail and foodservice brands worldwide are publicly committed to sourcing seafood responsibly from GAA’s Best Aquaculture Practices (BAP)-certified processing plants, farms, hatcheries, and feed mills. These include such familiar names as Albertson’s, Cub, Darden Restaurants, Food Lion, Fry’s, Giant, Giant Eagle, Gortons, Hannaford, IGA, Jewel-Osco, King Soopers, Kroger, Lunds, Meijer, Ralphs, Red Lobster, Safeway, Sam’s Club, Sea Pack, Supervalu, Target, Walmart, Wegmans, Winn-Dixie, and Yum! Brand restaurants.
Tilapia, among the most-consumed farmed fish in the U.S., is rated a “best choice” by Monterey Bay Aquarium when it is raised in recirculating systems (worldwide), ponds in Ecuador, or raceways (artificial channels) in Peru. Other farmed tilapia is a “good choice”—even from China and Taiwan, which were rated “avoid” a few years ago. Similarly, many sources of farmed salmon are rated “best” or “good alternative,” even though others remain “avoid.”
While seafood guides give much imported farmed shrimp a red light, domestic shrimp fares far better in general: It’s raised on a smaller scale and is subject to stringent safety and environmental standards and inspections. Certain shrimp from Canada also get a green light from Monterey Bay Aquarium, as do shrimp from Central and South American ponds and all shrimp raised in recirculating systems.
Closed recirculating tank systems alleviate problems of water pollution and fish escapes. Fish farmed in freshwater ponds at low density (meaning the fish are not crowded) are less prone to disease, the need for chemicals, and water pollution.
Mercury in Seafood: Safe Choices
Mercury levels in fish should be a prime concern for pregnant women, women who might become pregnant, and young children. Here’s the latest guidance from the FDA and EPA.
Updated mercury guidance
Topping the list of seafood contaminant concerns is mercury, which can harm the nervous system, especially during development. Earlier this year, the FDA and EPA released user-friendly advice to help pregnant women, women who might become pregnant, and parents of young children make healthy and safe fish choices. The agencies recommend eating two or three 4-ounce servings (before cooking) a week of fish lower in mercury. Previously they merely set a 12-ounce maximum intake for these at-risk groups; the minimum intake was added because many pregnant women eat little or no fish. The agencies note that other adults can also follow this advice.
The new mercury advice lists 55 types of fish that are either “best” or “good” choices, as well as seven large fish that should be avoided because of potentially high mercury levels. Be sure to vary your intake.
How fish are caught is important, too. For instance, pole- or troll-caught tuna tend to be smaller and thus have less mercury.
Fish caught by recreational anglers in lakes and rivers may have higher levels of contaminants; consult state advisories for how often you can safely eat such fish.
What about PCBs?
Fish may also contain PCBs (polychlorinated biphenyls) and other organic pollutants (such as DDT and dioxin). PCBs are banned industrial chemicals that persist in the environment and accumulate in the body. It’s not known whether PCBs cause cancer in humans, however, or how much it would take to cause it; they do cause cancer and other serious problems in lab animals.
Studies have found higher levels of PCBs and other contaminants in farmed salmon than in the wild fish. Farmed salmon get PCBs from their feed when it contains ground-up fish and fish oil. Wild salmon, which have a more varied diet, consume far less PCBs.
The most alarming findings about PCBs in farmed fish date from more than a decade ago, however, and since then many producers have switched to feed made from soy and other plant-based ingredients, reducing PCB levels (but also possibly reducing omega-3s). As recently as 2013, the Environmental Working Group did a small spot check of 10 U.S. grocery stores that still found high PCB levels in seven samples. But according to Seafood Health Facts, the greatest danger from PCB exposure now comes from recreationally caught fish, not farmed fish. It reports that most commercial seafood is well below the tolerance level of 2.0 parts per million (ppm) set by the FDA, with numerous studies reporting levels of PCBs ranging from 0.0005 to 0.100 ppm.
To reduce PCBs in fish, remove the skin and the fat beneath it with a sharp knife before cooking (or ask the fish seller to do it). Broil, bake, or grill fish on a rack instead of sautéing or frying. This allows the fat, where PCBs concentrate, to drain off, but still leaves plenty of beneficial omega-3s. Don’t use batter or breading—that traps the fat drippings. You can also remove the tomalley of lobsters and the “mustard” of crabs, in which contaminants accumulate. (No cooking methods can reduce mercury in fish, however.)
Drug residues are a concern with imported seafood—and some 85 percent of the seafood Americans consume is imported. The problem is that other countries have different standards for aquaculture, sometimes employing drugs banned here.
Veterinary drug residues were detected in fish inspected by the U.S., Canada, and the European Union between 2000 and 2009, according to a 2011 paper in Environmental Science & Technology. The most problematic imported seafood included shrimp and prawns, crab, basa (a type of catfish), eel, and tilapia, most or all likely farmed. Vietnam had the most drug violations, followed by China and then other countries in Asia, including Thailand, Indonesia, Taiwan, India, and Malaysia.
A 2015 paper in the Journal of Hazardous Materials found antibiotic residues in farmed fish purchased in the U.S., including tilapia from Panama and China. Though levels were relatively low, the authors note that the use of antibiotics in fish farming could nonetheless be contributing to the growing public health problem of drug-resistant bacteria.
On the other hand, a 2013 analysis in the Journal of Food Processing & Technology reported that of 36 samples of imported tilapia—mostly from Latin America—none tested positive for antimicrobials.
Your best recourse for limiting exposure to potential drug residues in farmed fish is to look primarily for U.S. or Canadian farmed seafood.
Also see Catch the Health Benefits of Fish.
Published November 17, 2017