Our Great Lakes

Can We Eat the Fish?

Many people love to grab a fishing pole and catch their dinner or at least enjoy time spent dipping a line in the water. About five million people fish in the Great Lakes every year. While many people fish for recreation, some depend on fish for food or for their livelihood in the sport and commercial fishing industries. Some Great Lakes fish are safe to eat and the situation is improving. Nevertheless, people who fish for or eat Great Lakes fish should be aware of published guidelines about how to avoid contaminated fish.

What is happening?

Over the years, the Great Lakes have been polluted by a wide range of heavy metals and chemicals. Some of these substances are persistent and do not break down readily in the environment. Several of them also build up in the food chain and can end up in the fish we like to eat.

Therefore, while fish are a good source of healthy food, you should avoid those whose tissues are too contaminated. The chemicals found in fish do not cause immediate sickness, but they can accumulate in our bodies over time and affect our health and that of our children. Some chemicals pose a considerable risk to a developing fetus, and their effects can include developmental problems in children. Women of childbearing age, pregnant women, nursing mothers, and children under age 15 all face greater risk of harm from toxic substances and should be careful to follow guidelines on what fish are safe for them to eat.

The good news is that since the 1970s, levels of many toxic chemicals in the Great Lakes ecosystem have declined and many sport consumption advisories have been eased. Despite these encouraging trends, advisories still exist about limiting or avoiding consumption of some fish from parts of all five Great Lakes.

Consult official fish consumption advisories for local conditions. Advisories are available from state, provincial, and Tribal and First Nations agencies dealing with Great Lakes fish issues, or online at http://www.great-lakes.net/humanhealth/fish/advisories.html

Figure 4:
Contaminants that cause fish advisories in Canada and the United States

What is being done?

We cannot smell, taste, or otherwise detect toxic chemicals in fish, so for decades governments around the Great Lakes have been testing fish in laboratories. Governments then advise the public about which fish are safe or unsafe to eat. Recommendations range from unlimited consumption to avoiding all fish of certain species in certain areas. Species at the top of the aquatic food chain, such as trout, salmon, and walleye, can build up higher levels of pollutants than fish that are not top predators. Generally, bigger and older fish accumulate more chemicals in their flesh than do smaller and younger fish. In addition to publishing information about contaminant levels, various organizations are helping people understand how to minimize exposure to pollution through their choice of fish and removal of fat before consuming it. Women of childbearing age and children are most sensitive to food borne contaminants.

Since 1970, governments have restricted or banned outright a number of key pollutants, such as PCBs and the pesticide DDT. Industries have also voluntarily reduced or eliminated releases of several substances into the environment. Many individuals have reduced their use of hazardous products and are safely disposing of unwanted amounts of such products. As a result, toxic chemical levels have been falling because, once the pollution flows are stopped, natural processes can begin to cleanse the environment.

The cleansing process, however, is being slowed down by some continued emissions of toxic substances from some sources. Contaminants from industrial smokestacks, power plants, and incinerators, as well as some pesticide sprays, are picked up from nearby - and even from halfway around the globe - and carried by winds, eventually to settle on the Great Lakes basin. Scientists are also monitoring potential risks from other chemicals that are turning up in the Great Lakes food chain. These include fire retardants containing polybrominated diphenyl ethers (PBDEs), a group of chemicals suspected of being able to disrupt the endocrine system, a regulator of many of the processes in our bodies.

Figure 5:
These salmon are high on the food chain and tend to accumulate such chemicals, so this indicator gives a good sense of trends in Great Lakes sport fish. The graphs show averages for each lake. Contaminant levels in coho and other fish may be higher or lower in different parts of a lake.