Michigan fishing industry is threatened
by quickly disappearing 'shrimp'
Gannett News Service
DETROIT -- One of the principal food sources for whitefish
is disappearing rapidly in the Great Lakes, a change that
threatens to shake up the food chain and hamper Michigan's
large commercial fishing industry.
Diporeia, a half-inch-long, shrimp-like creature that
lives on the bottom of the Great Lakes, has been wiped
out in portions of Lake Erie, Lake Michigan, Saginaw Bay
and Lake Ontario. About 17,000 square miles in the Great
Lakes no longer have diporeia.
''We have never seen anything like this,'' said Tom Nalepa,
the main research biologist studying the decline in diporeia
population. He works in Ann Arbor at the Great Lakes Environmental
Research biologists found densities of diporeia in the
1980s between 10,000 to 20,000 per square mile of sediment
in parts of the Great Lakes. Now in many of the same spots,
no diporeia are found, Nalepa said.
Diporeia, sometimes re-ferred to as a fresh-water shrimp,
is a main food source for many fish in the Great Lakes.
Fish that don't eat diporeia eat fish that do.
Whitefish have become one of the first casualties of
the loss of diporeia, re-searchers say.
Some of the fish caught now are much smaller than in
the past, Nalepa said. Studies on their stomachs have
found the fish have been feeding on zebra mussels and
another invasive species known as quagga mussels, which
are not as healthy for the fish as fat-enriched diporeia.
''The shells (from the mussels) pack their stomachs and
they think that they are full,'' Nalepa said. ''They are
getting skinnier and skinnier. The shell has no nutritional
value at all.''
In the past, whitefish could be found that were 2 feet
long and 5 pounds, said Jim Johnson, a research biologist
for the state Department of Natural Resources. Now whitefish
range from 20 to 22 inches. Some can't be used as filets
because they are too thin, he said.
''We are concerned on how this is going to affect the
future of the commercial fishing industry,'' Johnson said.