"What fish can I safely eat?"
"I
don't keep any fish because they're not safe to eat."
"I'll eat any fish
that comes out of the River."
"Haven't there been fish consumption warnings
issued lately?"
These are all questions and comments frequently heard regarding
pollution and fish in the Mississippi River. The extremes range from the
cautious "not eating any fish" to the reckless "eating all fish." Reality
lies somewhere in between.
Some fish in the river may take in contaminants from the water they
live in and the food they eat. Some of these contaminants build up in the
fish - and you - over time. These contaminants could harm the people that
eat them, so keeping your exposure to these contaminants as low as possible
is important. In both Minnesota and Wisconsin, the Department of Natural
Resources in conjunction with the Division of Health issue fish consumption
advisories that include the Mississippi River. These are developed to help
you plan what fish to keep as well as how often and how much sport fish
to eat. In Wisconsin, copies of the Health Guide are available at any DNR
office.
The main contaminant found in the Mississippi River is PCBs (polychiorinated biphenyls). PCBs, were once used in such products
as electrical transformers, cutting oils and carbonless paper and hydraulic
fluid. Although banned in 1976, PCBs do not decompose easily and, therefore,
remain in the environment. PCBs accumulate in sediments at the bottom of
the river.
Fish can absorb the PCBs from the water, suspended sediments or food.
The good news is that the levels of PCBs in the Mississippi River are slowly
decreasing because the PCBs already in the sediment are being buried as
the river deposits new clean sediment.
PCBs are a health concern because they are suspected to be cancer causing,
and research has shown they impair reproduction in some animals. PCB's
have also been linked to developmental and growth problems in children
born to women who regularly ate Great Lakes fish.
The amount of PCBs in a fish taken out of the Mississippi River is dependent
upon many factors. The kind of fish, its size, age, fat content, diet and
location all can influence the amount of PCBs. Usually older and larger
fish of the same species will have a greater amount of PCBs. Fish from
Pools 3 and 4, which extends from Hastings, MN though Lake Pepin, will
have more PCBs than fish from pools downstream. PCBs are stored in fat;
therefore, a fish with higher fat content such as a carp would likely contain
higher concentrations of PCBs than a smaller, leaner species such as a
perch. The Health Guide has information about which fish should be avoided.
The guide lists species, sizes and locations.
A person can take steps to avoid exposure to PCBs and still eat fish
from the Mississippi River. Eat smaller, leaner fish. Eat fish that are
less contaminated (panfish usually contain low or undetectable PCB levels),
and remove all traces of fat and skin before cooking. If you are pregnant,
nursing an infant or under 15, avoid eating some fish as listed in the
Health Guide.
There are some differences between the fish advisories listed in the
Health Guides for the two states, but in general the recommendations are
similar. In the past Minnesota treated the Mississippi River as one unit
from St. Anthony Falls, near the Twin cities, to the Iowa border, consequently
there were more extensive health warnings for fish consumption. This year,
Minnesota breaks the Mississippi River into five units. (Wisconsin breaks
the river into three units.) The differences in the guides may be a result
of differences in how health risks are interpreted, according to the Minnesota
Fish Consumption Advisory.
1998 Wisconsin Recommendations for Pools 5 through 9 (Alma, WI to Lynxville, Wi)
Channel catfish and walleye larger than 20" should not be eaten more than one meal a month.
Walleye less than 20", all carp, white bass, black crappie -one meal a week
Other panfish -unlimited
Return to Mississippi River Home Page
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This is part of an ongoing series about the plants, fish, wildlife and issues pertaining to the Mississippi River. For questions or comments, write to Mississippi River Tidbits, Wisconsin DNR, State Office Bldg., Rni. 104, 3550 Mormon Coulee Rd., La Crosse, WI 54601
