The Mad Hatter in Alice in Wonderland most likely had a pretty good reason for being mad—before the use of mercury was banned in the 1940s, hat makers used it in their craft which left many of them drooling, twitching, lurching, befuddled and mumbling. These days, you don’t have to be in the millinery business to be worried about mercury—it is has invaded our waters and consequently much of the fish we eat.
And if the mercury isn’t a problem, there are the dioxins and PBCs. Oh, and the issues of marine sustainability, which are becoming increasingly urgent. Meanwhile the Harvard School of Public Health says that eating a modest amount of fish per week reduces the risk of death from coronary heart disease by 36 percent. Ack! What to do?
By understanding the threats that the marine environment is facing we can make informed decisions about eating fish in a sustainable way—and by learning about pollution issues as they relate to the water, we can steer clear of contaminated fish. Here are the issues, then we will show you how to navigate a non-baffling trip to the fish market.
The ocean’s bottom is a vibrant and thriving ecosystem, that is until a bottom trawler or heavy dredge net crushes through leaving a rubble of the 700-year-old coral and other fragile life there. The living seafloor needs centuries to grow back, but with “trawl fleets” chugging along to keep up with our hunger for fish, the seafloor never gets a change to recuperate. This may be the single worst harm done to the marine environment by man. If you’re able, find out the method by which the fish was caught. Many restaurants and stores are now listing the fishing method, and there is increasing lobbying to have this information more widely available. Habitat-friendly fishing methods include longlining, hook-and-line fishing and trap fishing.
American consumers made a huge impact on the fishing industry when they began boycotting tuna because of the toll tuna fishing took on dolphins. Which is great, but the problems continue. The United Nations Food and Agriculture Organization cites that one in four animals caught in fishing gear dies as bycatch—fish that are unwanted. Tons of dead fish are tossed out; maybe they have no market value, are too small, or the boat lacks the proper permit. They are just thrown out. Dolphins, sea turtles, seals, whales and even seabirds are all, regularly, accidentally caught and killed.
Overfishing happens when the rate of catching fish exceeds the rate at which they can reproduce. It’s as simple as it sounds. As fish that were once plentiful become harder to find, fishing fleets move on to new species, which then in turn become overfished. Especially vulnerable are slow-growing species, such as orange roughy and Chilean sea bass.
If only the answer was as easy as “fish farms.” To help fortify the demand for seafood, an aquaculture industry has risen that produces nearly one-third of the seafood we eat. But not all fish farms are kind to the environment.
Most oysters and many of the clams and mussels we eat are farm-raised. These farms do little to disturb the ecosystem—hurray!—they even improve water quality (the mollusks work as filters) and since they must be grown in non-polluted water, these farms are often very involved in clean water initiatives.
The bad news comes from fish raised in net pens, like salmon. Over-crowded pens pollute the water and fish become diseased—pollution and disease spread to wild fish, and antibiotics used also leak out into the water. Escapees can overtake wild habitats, and the fishmeal used for feed is often made with fish that contain toxins. Eating wild salmon is okay, check the guides below for the best choices.
In tropical countries, countless coastal mangrove forests have been cut down to make room for farms to satisfy the international demand for shrimp. This is not a sustainable practice—waste builds up in the farm ponds making them uninhabitable for shrimp. The farm moves on, leaving a destroyed coastal environment in its wake. Mangrove forests are crucial for protecting coastal areas, the prognosis here is bleak.
Mercury occurs naturally, but is also a product of industrial pollution. In this guise it falls from the air and settles in our waterways—there, it is turned into methyl mercury and absorbed by fish. As it goes, larger and older fish have a longer time to build up mercury than smaller and younger fish. Plus, large predatory fish at the top of food chain generally have higher levels of mercury. There is no debate about the toxicity of mercury poisoning from fish. It is most threatening to prenatal development—thus pregnant women are advised to practice extreme caution when eating fish. Young children and women planning on becoming pregnant are always advised to watch their mercury as well. Although the FDA had determined safe levels of methyl mercury consumption for adults—I’d rather just avoid the risk of neurological damage altogether, thanks. (The EPA has established stricter guidelines than the FDA, based on more recent and complete studies as well as the consideration of other pollutants in addition to mercury.)
Beyond mercury there are other industrial chemicals such as PCBs and dioxins, and pesticides such as DDT and dieldrin, that our infiltrating our waterways and our fish. We can thank industrial and municipal discharges, agricultural methods, and storm water runoff for this—as well as good old rain, which can simply rinse these contaminants from the land into streams and rivers. These chemicals then bioaccumulate in the skin, organs and other fatty tissues of fish. Many of these pollutants settle at the water’s floor which strongly affects bottom-tending fish—for example, wild striped bass, bluefish, American eel, and sea trout tend to be high in PCBs.
The Effects of Contaminants
Mercury, PCBs and dioxins build up and concentrate in our bodies over time. Health problems that may result from eating contaminated fish range from minimal to birth defects and cancer. It can take 5 years or more for women in their childbearing years to rid their bodies of PCBs, and 12-18 months to significantly reduce their body burden of mercury. Mothers who eat contaminated fish before becoming pregnant may have children who are slower to develop and learn. Developing fetuses are exposed to stored toxins through the placenta.
Uhm, So Why Eat Fish?
It’s about now that I am thinking, “well, actually…don’t think I really want to eat fish anymore”—which is where I always end up in this fish maze. But then they come out with the studies and statistics that are just so hard to ignore. I keep going back to that Harvard School of Public Health study showing that eating a modest amount of fish per week reduces the risk of death from coronary heart disease by 36% and overall mortality by 17%.
Omega-3 Fatty Acids
Fish is a high-protein, low-fat food that provides great health benefits. In the marine food chain, algae make one type of Omega-3 fatty acid, which is then consumed by zooplankton and elongated to form two other types of Omega-3 acids. Those zooplankton are in turn eaten by finfish and shellfish, resulting in a high concentration of Omega-3. These Omega-3 fatty acids help maintain cardiovascular health and are important for prenatal and postnatal neurological development. They may reduce tissue inflammation and alleviate the symptoms of rheumatoid arthritis. Other maladies in which omega-3 may play a beneficial role include cardiac arrhythmia (irregular heartbeat), depression and irritable bowel syndrome.
The Basic Rules
• Avoid shark, swordfish, king mackerel, or tilefish—they contain the highest levels of mercury.
• The most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.
• Canned tuna comes in white and light. Canned white tuna consists of albacore, a large species of tuna that accumulates moderate amounts of mercury, and should be eaten cautiously. Canned light tuna usually consists of a smaller type of tuna with approximately thirty percent the mercury levels of albacore.
•Check the EPA National Listing of Fish Advisories–a map tool that can tell you specific information about the safety of fish from your local lakes, rivers, and coastal areas.
•Download a pocket guide—see below.
Cooking to Reduce Pollutants
Since mercury binds to the protein in fish tissue, it cannot be removed by cooking. However following these guidelines can help reduce the level of PCBs, dioxins and some pesticides, as those pesky pollutants concentrate in the fatty tissue.
• Remove skin, fat, internal organs, and lobster and crab roe, where toxins can accumulate.
• Drain fat away when cooking.
• While fish sticks and fried fish fillets are usually made from low-toxin pollock, be careful of what you fry at home. Frying locks in pollutants in the fish’s fat, while other cooking methods allow that fat to drain away.
To make selecting fish a little less bewildering.
Environmental Defense downloadable
Pocket Seafood Selector lists the best and worst choices for the environment, and also notes which ones within those categories are high or low in environmental contaminants.
Oceans Alive Contaminated Fish Chart—offers consumption guidelines with best and worst eco-choices.
Monterey Bay Aquarium Seafood Watch provides pocket size downloadable Seafood Watch Pocket Guides—these are regional and up to date and allow you to select fish from your part of the country.