UConn study: good news for fishermen

For many Connecticut outdoor enthusiasts, spring means the beginning of fishing season. This year, anglers will be pleased to know that a new University of Connecticut study has found that mercury contamination levels in the meat of largemouth bass from Connecticut lakes were lower in 2005-06 than levels documented a decade earlier.

While this is good news on the improving quality of fish and the aquatic environment, the study also reveals, however, that despite the lower mercury contamination, the toxic metal is still present at levels that merit a continuation of the current statewide fish consumption advisory.

The Connecticut Department of Public Health advises young women who are or may become pregnant, nursing mothers and children under age 6 to limit eating locally caught freshwater fish to one meal per month because of the risks posed by mercury to this high-risk group of people. State officials have advised the rest of the public to limit consumption to one meal per week. The statewide consumption advisory excludes stocked trout that are raised in hatcheries and released in spring and fall stocking programs into ponds, lakes, rivers and streams around the state.

    u    u    u

There are of course, many health benefits to eating fish. Eating some of the fish you catch is also a longstanding cultural heritage that helps us understand both where food comes from and the value of conserving a clean and healthy environment. Fishing is also fun, relaxing, and a great way for families to enjoy the outdoors.

Connecticut and U.S. health officials believe the widespread elevated levels of mercury in freshwater fish found in the Northeast are largely the result of mercury released from coal-burning power plants — many far away from Connecticut waters. Once in the air, the toxic metal can travel huge distances before entering soil and water.

Once mercury settles into watersheds and enters the water, it is transformed by water-borne bacteria and then can enter algae, which are eaten by plankton, which are eaten by little fish, which in turn are eaten by bigger fish like largemouth bass. At each step in the food chain, the mercury becomes more concentrated — this process is called bioaccumulation. Mercury is a naturally occurring metal, but becomes toxic to human and animal consumers when highly concentrated in fish flesh.

    u    u    u

Because of mercury’s toxicity, both federal and state public officials have agreed to efforts to reduce manmade mercury emissions in power plants. The federal Clean Air Act has imposed stricter standards on coal-burning plants and smokestack “scrubbers†have been placed in many facilities in the upper Midwest and Canada that send mercury toward Connecticut.

The new UConn study suggests that perhaps these efforts are starting to pay off. The study is the second statewide assessment of mercury levels in fish from Connecticut lakes and the first to compare testing data from 1995 to the present. Funding for the current study was provided by the Connecticut Department of Environmental Protection.

Lakes were chosen from every region of the state and fish were collected by electrofishing, a sampling technique that generates an electric field in the water to stun fish so they can be easily netted. Additional fish were donated by anglers participating in fishing tournaments.

Largemouth bass were used for the study because these predators represent the top of the food chain in most Connecticut lakes and therefore have the highest expected levels of mercury contamination.

The UConn study also experimented with a new non-lethal biopsy method to determine mercury levels in the fish. Following existing protocols, fish were euthanized and the fillet (the muscle meat on one side of the fish) was removed and then blended together and analyzed for mercury contamination levels. In the new experimental method, small biopsies were removed from random fillets prior to blending and the experiment showed that the biopsies could be taken from fish and used to determine mercury levels that are comparable. Other states have already transitioned to the biopsy method and use this type of non-lethal monitoring without removing fish from the wild — Connecticut could now do the same.   

    u    u    u

The contamination problem is pervasive and public health officials believe that even if all manmade mercury emissions were stopped, it would take 15 to 20 years before mercury levels in the environment and fish would drop to low enough levels for nonmoderated human consumption. Future monitoring will be needed to determine when the consumption advisories based on mercury can be relaxed and hopefully one day removed.

There are particular water bodies in Connecticut that have additional advisories due to higher than average mercury levels and other environmental contaminants. Anglers should refer to ct.gov/dph or call 877-458-3474 for more information. A summary of current consumption advisories is always included in the annual Angler’s Guide distributed by the Department of Environmental Protection Fisheries Divisions; the guide is available at most town clerks and tackle stores as well as online at ct.gov/dep.

Jason Vokoun is assistant professor of fisheries and wildlife in the Department of Natural Resources and the Environment at the University of Connecticut.