Double-crested cormorants are an unwelcome sight in many communitiesaround the Great Lakes. Anglers say the birds have devastated fishpopulations- and in some cases, the local economy. Until recently,scientists weren’t sure why cormorants were having such a large effect.The Great Lakes Radio Consortium’s Karen Kelly reports on new researchthat may point to an answer:
Double-crested cormorants are an unwelcome sight in
many communities around the Great Lakes.
Anglers say the birds have devastated fish populations
– and in some cases, the local economy.
Until recently, scientists weren’t sure why cormorants
were having such a large effect.
The Great Lakes Radio Consortium’s Karen Kelly reports
on new research that may point to an answer.
In New York, Oneida Lake is known as “the walleye
Every year, hundreds of anglers descend on the local
community, hoping to catch “the big one”.
But those big fish aren’t as common as they used to
Tony Buffa is a charter captain on Oneida Lake and on
nearby Lake Ontario.
He says ever since the cormorants arrived, the bigger
walleye are much tougher to find.
He suspects that’s because the cormorants are
eating them before they grow to 15 inches – that’s the
legal limit for anglers.
“A ‘young of the year’ walleye is a 6 or 7
incher. And then all of a sudden when you’d expect
that same group to make it to an adult stage, there’s
the disappearance in that 6 inch range to the 14 inch
And researchers say the anglers aren’t just imagining
this. They’ve found that the six to 14 inch range is
exactly the size the cormorants like to eat.
Connie Adams is a biologist at the Cornell University
field station on Oneida Lake.
She spent the past 6 years analyzing the diet of the
lake’s cormorant population.
“When I began this study, I thought how could 300
pairs of birds possibly have a very large impact on
fish spread over a 20 thousand hectare lake. It just
didn’t seem intuitively correct that cormorants were
causing the decline anglers were attributing to them.
But when we got the numbers, it’s undeniable.”
Adams estimates that most years, the cormorants eat
more than 20 percent of the walleyes between the ages
of one and three.
That’s when the fish are in the six to 14 inch range.
So by the time the fish reach adulthood at age four,
the birds have eaten more than half of them.
But Oneida Lake’s cormorants are not unique. Those big
fish have also been scarce in some fishing communities
on Lake Erie and Lake Ontario.
Jim Johnson is a researcher with the U.S. Geological
His work on Lake Ontario found evidence that
cormorants were eating smallmouth bass over 10 inches
Johnson says this a new finding in cormorant research.
”The implications of these two studies are that,
for the first time they’ve found cormorants can have a
discernable impact on gamefish population. At the same
time, the bulk of the literature suggests that
cormorants often do not cause any problems to gamefish
populations so I think what these studies are telling
us is that you just can not generalize too much with
But the anglers say these studies provide the evidence
they’ve been waiting for.
Many support a bill in Congress that’s calling for a
hunting season on cormorants.
State biologists, though, argue such a season isn’t
necessary, because they’ve found other ways to control
On Lake Ontario, they’re killing eggs.
And biologists are destroying nests to prevent the
cormorants from laying eggs.
Some environmental groups oppose these actions, while
the anglers argue it’s not enough.
Biologist Connie Adams meanwhile says she doesn’t
expect the new findings will lead to a change in
policy – but she says they do lend credence to the
plight of many Great Lakes fishermen.
For the Great Lakes Radio Consortium, I’m Karen Kelly.