targeted for DNR study
Bird's fish-eating habits concern Green Bay anglers
By Jim Lee
Wisconsin Rapids Daily Tribune
Published June 20, 2004
Wisconsin anglers relish a meal of yellow perch, but so
do cormorants and white pelicans.
As the perch population has declined in the waters of
Green Bay, angler bag limits have been curtailed, but
no such dietary restrictions apply to wildlife.
In an effort to satisfy angler concerns, the Department
of Natural Resources has launched a $90,000 study of the
dining habits of the two major fish-eating bird species
on the bay.
"The reason the study is coming about is the U.S.
Fish and Wildlife Service has given states the authority
to manage cormorant populations," said Sumner Matteson,
DNR avian ecologist.
"Commercial and recreational fishermen perceive
cormorants as heavily preying on yellow perch, and they
have asked what the state is doing about it.
"The limited data we have suggest perch are a small
part of their diet, but we need this study to provide
the best assessment of the situation."
Cormorants and pelicans are suspects because their numbers
skyrocketed just about the time the perch population on
Green Bay plummeted. Perch numbers declined 90 percent
between 1988 and 2000.
Cormorants, a historic presence in Wisconsin, nearly
disappeared from the state by the early 1960s, a victim
of DDT, habitat loss and illegal human activity. Largely
through DNR restoration efforts, the population has rebounded
from a low of 66 nests in 1973 to a current level estimated
at more than 11,000 breeding pairs, Matteson said.
"About 81 percent of the breeding takes place on
four islands (Cat, Spider, Jack and Hat) in Green Bay,"
White pelicans have a historical presence in the state,
but the first documented nesting occurred just 10 years
ago, Matteson said.
In 2003, the DNR found 907 pelican nests, more than 400
in lower Green Bay.
Why did Wisconsin, previously shunned as a nesting site,
suddenly become a pelican incubator?
"That's the $64 question," Matteson said. "No
one really knows for sure."
Both cormorants and pelicans, which typically arrive in
Wisconsin waters during April and depart by the end of
November, feed heavily on fish. Cormorants reportedly
consume about one pound of fish daily, with their favored
targets in the 6- to 12-inch range.
Foraging habits differ. Cormorants are capable of diving
fairly deep in search of prey, but white pelicans tend
to feed in groups for the purpose of herding small fish
in shallow water.
Matteson said previous studies found alewife, stickleback
and other forage species predominated in the cormorant's
diet. Since that time, alewife numbers in Green Bay have
declined while yellow perch appear on the threshold of
making a comeback.
Bill Horns, DNR Great Lakes fisheries specialist, said
the department is in a good position to evaluate the impact
of cormorant and pelican predation on the bay fishery,
adding that a good yellow perch hatch in 2003 should produce
fish of a size attractive to cormorants by this summer.
"The stars are in alignment for a good study,"
Results will be of interest to anglers on inland waters
where cormorants have taken up residence in recent years.
Matteson said flowages have become particularly attractive
to cormorants, while Horicon Marsh harbors more than half
the state's pelican nests.
The study is funded for two years, though Matteson says
a third year is desirable to enhance scientific accuracy.
Funding comes from a DNR settlement with paper companies
for damage caused by past pollution on the Fox River and
Cormorants and white pelicans aren't the only perch predators
recently restored to abundance on the bay. Walleye, spotted
musky, salmon, trout, smallmouth bass, white bass, catfish
and sheepshead are on hand in larger numbers than before
the previous perch heyday.
Add to that mix the uncertain impact of undesirable exotic
species, including zebra mussels, white perch, round goby,
milfoil and other environmental factors, and it's a fair
bet that trimming the cormorant population won't be the
end-all solution to the bay's yellow perch woes.
The most favorable outcome would be to find the perch
population has shrugged off this wave of outside factors
and is rebounding on its own.