Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

Photo of a fish dinner © Steve Apps

"Let's go out for fish."
© Steve Apps

December 2011

Give in to fish fervor

But chew over this advice before you consume.

Sonya Rowe

Crowded supper club parking lots on a Friday night tell the story. We love fish fries. They've been a time-honored and tasty tradition in the Badger State since the days of prohibition when tavern owners needed a way to lure customers in without liquor. And while an occasional Friday night fish fry is a treat, even more so, many families savor those sunny afternoons out on the lake or river catching fish and then preparing them together using a recipe that contributes to a healthy and balanced diet.

Ice fishing. Fly fishing. Charter boat fishing. Shore fishing. The opportunities to feed a family by fishing and to have fun doing it are available year-round and statewide...with caution.

Nutritionists know that fish are low in fat and high in protein and a great source of vitamins and minerals. Fish, like bluegills and perch, have less than half the calories of a hamburger. Many doctors suggest that eating one to two meals of fish a week can benefit your health.

Even though fish are a great source of nutrition, some fish also accumulate contaminants from their watery homes. These pollutants, such as mercury, are then passed on to wildlife and humans when they eat contaminated fish. Mercury is not peculiar to Wisconsin. Dr. James Hurley, director of the Environmental Health Division at the Wisconsin State Laboratory of Hygiene, recently attended the 10th International Conference on Mercury as a Global Pollutant. He says, "Governments around the world are working toward a global agreement to protect human health and the environment from the harmful effects of mercury."

Mercury levels in some ocean species, for example, prompted the Food and Drug Administration (FDA) to issue national advisories. The FDA sets tolerance and action levels for contaminants in purchased fish, but the FDA and the Environmental Protection Agency (EPA) defer to the various states' fish monitoring and advisory programs for advice on eating fish taken from local waters.

Mercury and polychlorinated biphenyls or PCBs are the primary contaminants found in fish caught in Wisconsin. The good news for anglers here, though, is that Wisconsin's fish contain less mercury and PCBs than they did in the past.

"The data we've collected over the past 40 years show general improvements in mercury and PCB levels compared to earlier years," says Candy Schrank, Department of Natural Resources fisheries toxicologist. "Studies using our data support assertions that fish respond to sediment cleanup and mercury emission reductions, and this is good news for anglers and for state and local economies."

Where are you in the exposure spectrum?

More than 80 percent of Wisconsin adults eat fish or shellfish, including freshwater and saltwater species purchased from grocers, restaurants or fish farms. Many people regularly eat fish from Wisconsin waters, either catching their own or purchasing fish such as lake whitefish or chubs that are commercially harvested from Lake Michigan or Lake Superior.

Some people take great care with how much and what kinds of fish they eat. But others may unknowingly be exposed to unsafe amounts of contaminants by eating too many larger predatory fish such as walleye from northern Wisconsin lakes or king mackerel from the fish market, or by consuming too many fish from waters with high levels of contaminants. It pays to be informed.

As a fish consumer you should ask yourself: How frequently do I eat large predatory fish? Do I know what the consumption recommendations are for my favorite fishing spots? Where did the fish I am eating come from?

Photo of man with fish © John Cichosz
Smaller is better when it comes to eating fish like this tasty walleye.
© John Cichosz

Dr. Lynda Knobeloch, a Wisconsin Department of Health Services researcher, recently described seven cases involving 14 Wisconsinites who were found to have high blood mercury levels linked to high fish consumption. Some ate as much as nine fish meals per week before being tested for mercury. Three people reported vague symptoms of mental confusion, sleep difficulty, balance problems and blurry vision. Four of the cases included older anglers who ate their catch from northern Wisconsin lakes. The three people with symptoms reported improvements and saw their mercury levels return to normal after they reduced their predatory fish intake.

In explaining her findings, Knobeloch concluded, "We hope that these documented Wisconsin cases were exceptions, but fear that some avid anglers who fish northern lakes may be eating too many fish with high concentrations of mercury."

Dr. Knobeloch later used hair samples from volunteers to test for mercury exposure. She compared hair mercury levels in 2004 to those in 2008. Participants tested in 2004 that had hair mercury exceeding 1 ppm (parts per million), the upper end of safe mercury exposure, were advised to continue to eat fish but select fish low in mercury. Four years later, this group had significantly lower hair mercury overall. Most reported eating less fish, eating different types of fish, or both, demonstrating that eating species with lower mercury levels or eating less fish can reduce your exposure to mercury.

Another Wisconsin study compared PCBs in the blood of Great Lakes charter captains, anglers and infrequent fish eaters. The participants had eaten fish for an average of 30 years including purchased fish, fish caught from Wisconsin waters and from the Great Lakes. On average, they ate 25 meals of fish per year (or about two meals per month) when the study began in 1993 and 1994 and 18 meals per year in 2005. Over this time period, PCB levels declined in 80 percent of the participants, which was attributed in part, to eating fewer fish meals and to lower PCB levels in fish following restrictions on PCB production and use. During this time, Lake Michigan anglers also switched from eating lake trout – a long-lived fatty fish with higher PCBs – to eating more salmon, fish that tend to be lower in PCBs.

Reducing your exposure to contaminants

People who frequently eat fish from Wisconsin waters should follow Wisconsin's fish consumption advice issued jointly by the Department of Health Services and the Department of Natural Resources. You can still get the health benefits of your catch, while reducing contaminant exposure to you and your family. The advice is a set of recommendations on how many meals of Wisconsin fish you and your family should eat in a given time period.

Fillet your fish to reduce PCBs

Graphic showing how to fillet a fish © DNR File

Contaminants vary with the species of fish as well as the size of the fish and water in which it lives. Because most fish contain mercury, start by following the statewide safe-eating guidelines when eating fish from most of Wisconsin's inland waters (Fish Consumption Advisories). The webpage also presents information that compares popular purchased species. Fish buyers may also consult FDA's website (Food Safety).

Also, check the exceptions to the statewide advice to find out if your fishing spot is one of 153 areas where higher levels of contaminants have been found in fish and more stringent advice for fish consumption is necessary.

The Department of Natural Resources monitors fish throughout the state on a rotating schedule depending on the type of water, pollutant and if there has been cleanup activity. Contaminants in fillets are quantified by the Wisconsin State Laboratory of Hygiene and by using data from other states for border waters and for lakes sampled by the Great Lakes Indian Fish and Wildlife Commission (GLIFWC).

The Choose Wisely booklet, available at your local DNR office or from the DNR website (Fish Consumption Advisories), contains a list of lakes and rivers where some species should be eaten less frequently.

Polychlorinated biphenyls or PCBs

PCBs are man-made chemicals first used in the 1940s in electrical equipment, industrial processes, and carbonless copy paper manufacturing and recycling. Wisconsin began issuing fish consumption advice in the 1970s after PCBs were detected in Lake Michigan, Green Bay and parts of the Wisconsin River. In 1979 the United States banned PCB manufacturing altogether.

PCBs resist degradation, attach to sediments and build up in fish and wildlife. The State of Wisconsin and the federal government have worked with various responsible parties to commit significant resources toward removing PCB contaminated sediments from rivers and harbors that historically received discharges from operations that used or handled PCBs.

Fish take in PCBs from contaminated sediments when they eat plants, algae, insects, zooplankton and crayfish. PCBs and other similar chemicals bioaccumulate (build up) and become more concentrated in larger fish or other animals that eat them. The amount of PCBs found in fish depends on species, age, size, fat content and foraging habits. Fish that live in areas with PCBs in the sediment have higher concentrations of PCBs. Since PCBs bioaccumulate in the fatty tissue of organisms, fatty fish like carp and catfish may have higher PCB concentrations.

As a general rule, larger older predator fish are more likely to have higher concentrations of contaminants than younger smaller fish from the same waterbody.

Mercury reductions underway

The Department of Natural Resources first issued fish consumption advice due to mercury in 1985 when high levels of mercury were found in some fish species in several northern Wisconsin lakes far from any direct sources. Unlike PCBs, mercury is a naturally occurring element, but human activities such as mining, burning fossil fuels, metals production and waste incineration release mercury to the atmosphere.

Mercury, released as elemental, reactive gaseous, or particulate mercury, ends up in lakes and streams through rain and snow, dry deposition and runoff. Today, coal burning is one of the main sources of mercury entering the atmosphere. Some of the emitted mercury is deposited on land and water locally or regionally. Some may be transported longer distances with weather systems, becoming part of the global mercury cycle.

Deposited mercury must first be converted to methylmercury before it can be taken up by aquatic organisms. This conversion is greatest where oxygen levels are very low and acidity and sulfates are high, conditions typical in some wetlands and northern lakes. That's where certain types of anaerobic bacteria convert mercury to methylmercury that then enters the aquatic food chain and accumulates in fish and fish-eating wildlife and humans.

Wisconsin's safe eating guidelines

Chart of safe eating guidelines © DNR File

**Some lakes and rivers contain higher levels of mercury or PCBs. See Fish Consumption Advisories for exceptions.

Dr. Carl Watras, a mercury researcher for the Department of Natural Resources and UW-Madison, notes that although levels of mercury in lake water and fish have declined along with recent reductions in "mercury rain," future improvements will depend on further reductions in mercury deposition and several other factors such as climate and acid rain.

Conditions that stimulate methylmercury production and bioaccumulation can affect the amount of mercury in fish. Watras' research in northern Wisconsin indicates that acid rain and extreme changes in water levels stimulate methylmercury production in our lakes. Extreme changes in water levels may occur more frequently in a future climate that is both warmer and wetter.

The Department of Natural Resources has been working with local communities for more than a decade to reduce the use of mercury-containing products, promote mercury recycling, reduce mercury spills and reduce air emissions from coal-fired power plants and other industrial sources, according to Marty Burkholder, policy specialist for the DNR Air Management program.

Recently, Wisconsin utilities were required to reduce mercury emissions by 40 percent. ERCO Worldwide, which owns and operates a chlor-alkali plant in Port Edwards that until 2009 was responsible for about 20 percent (almost 1,000 pounds) of the annual mercury emissions reported in Wisconsin, voluntarily moved to a new technology that eliminated mercury emissions from its manufacturing processes.

A new law recently banned the sale of certain mercury-containing devices including fever thermometers, barometers, toys and thermostats.

Dioxins, fluorinated compounds and blue-green algae

Dioxins, shorthand for a family of related chemicals (polychlorinated dibenzodioxins and polychlorinated dibenzofurans), are unwanted byproducts of several manufacturing processes and are found throughout the world.

In the past, these contaminants were discharged to some of Wisconsin's waters when companies used chlorine to bleach wood pulp to make paper. Now, with that source under control, the main source of dioxins to the environment in the United States is thought to be the uncontrolled open burning of waste materials such as plastics, asphalt and rubber.

Dioxins can bioaccumulate and, as a result, fish consumption advice for dioxins is issued for carp and channel catfish on some stretches of the Wisconsin River.

A fluorinated compound called perfluorooctane sulfonate (PFOS) is the most recent addition to the list of chemicals that have prompted consumption advisories. PFOS belongs to a group of chemicals called surfactants that have unique properties that make materials resistant to stains, oils and water. Fish consumption advice due to PFOS is in place for bluegills and crappies taken from certain sections of the Mississippi River.

Under certain conditions that are not well understood, blue-green algae can produce toxins that also can be found in fish. The health risks of eating fish exposed to these toxins are largely unknown. Anglers are advised to eat in moderation any fish taken from waters that look like pea soup, green or blue paint, or have scum or puffy blobs on the surface of the water.

When filleting fish from waters that might be contaminated, avoid cutting into the guts where the algal toxins accumulate, and rinse the fillets well before cooking. Or, better yet, choose another water to fish. To learn more about blue-green algae visit Blue-Green Algae in Wisconsin Waters.

How contaminants affect our health

Health experts encourage us to include fish in our diets but to limit the intake of fish taken from contaminated waters, and to try to eat smaller, younger fish. Health risks from eating fish depend on how often you eat it and the contaminant levels in the fish that you eat.

Mercury from the fish you eat can build up in your body, reaching levels that affect the nervous system. Prenatal and early childhood exposures can cause lifelong changes in brain function affecting learning, coordination and reaction times. In adults and older children, mercury can affect cognitive thinking, coordination, balance, vision, hearing and speech. It takes our bodies 60 days to eliminate half of the mercury we ingest, so fish with higher mercury concentrations should be eaten less frequently.

The health effects of eating fish contaminated with PCBs have been widely studied in animals and humans. Studies indicate that people exposed to PCBs are at greater risk for a variety of health problems. PCBs can cause developmental disorders in children born to mothers who eat contaminated fish before and during pregnancy. PCB exposure may cause reduced birth weights and conception problems.

PCBs also are linked to an increased cancer risk, as well as immune and endocrine problems such as diabetes and thyroid problems. PCBs are stored in body fat for years and the burden in the body increases over time as one eats more contaminated fish.

Essential fats are good news

You've probably heard about good and bad fats. In addition to being a great source of vitamins, protein and minerals, fish are one way to add more healthy fats to your diet. Omega-3 and 6 fats are essential for normal brain and nerve function and may lower the risk of heart disease and type 2 diabetes. The only way to get these good fats is from fish, nuts, vegetable oils, flaxseeds or supplements. Some species of fish like herring, mackerel, sardines, wild salmon and trout are excellent sources of omega-3 fats.

Dr. Henry Anderson, state health officer from the Wisconsin Department of Health Services who has worked on fish consumption advice since the 1970s notes, "While there is more to learn about the importance of these essential nutrients and how much is in Wisconsin fish, most people would benefit by adding these foods to their diets."

That means you can help keep the Friday fish fry tradition alive and well in Wisconsin at home or in the supper club. Go ahead and dig out your favorite fish recipe or accept that frequently uttered Friday invite, "Let's go out for fish." Answer the call for coleslaw, tartar sauce and a buttered roll on the side. Mull over your choice of potato, soup or salad. Just be an informed consumer or angler and choose the main dish thoughtfully before feasting on that flaky fare.

Sonya Rowe is a communications specialist for the DNR Fisheries Management program.

Submit your healthy Wisconsin fish recipe

Twenty-five recipes featuring a variety of Wisconsin fish species will be featured in an online cookbook. We'll publish at least two recipes in an upcoming issue of Wisconsin Natural Resources magazine. We'll base our selection on:

  • Originality and creativity
  • Healthiness
  • Ease of preparation
  • Species of fish
  • Added details on the recipe's origin and how or where you catch your fish

Recipes must be your own, feature Wisconsin fish species and be cooked (not smoked or pickled). One entry per household. Submit using our form at Fishing Wisconsin by April 1, 2012.

More information
  • Wisconsin Department of Natural Resoures at Fish Consumption Advisories
  • Wisconsin Department of Health Services at Eating Safe Fish
  • Are you a Wisconsin male angler 50 or older? The Wisconsin Department of Health Services invites you to participate in a brief survey on fishing, fish advisories and the fish meals you eat. Your participation will improve information that we provide to Wisconsin anglers on healthy fish consumption. Visit Wisconsin Anglers Study.