Wisconsin fisheries biologists have detected
a new species of nonnative fish in Duluth/Superior harbor
on western Lake Superior.
They suspect the single tubenose goby discovered during
a routine survey in late September was a stowaway on
a vessel from the St. Clair River, which connects lakes
Huron and Erie.
The discovery of the tubenose goby represents its
first occurrence outside of the Western Erie/St. Clair
River area, according to Dennis Pratt, a fisheries biologist
with the Wisconsin Department of Natural Resources.
It adds to the growing list of nonnative species introduced
by ships and smaller vessels transporting cargo globally
and within the Great Lakes.
The tubenose goby is a Eurasian fish species native
to the Black and Caspian seas. It was first discovered
in 1990 in Michigan waters of the St. Clair River and
has since been found in northwestern Lake Erie.
"Duluth/Superior harbor is one of the largest shipping
ports on the Great Lakes, and more than one-quarter
of the fish species now found in the harbor are not
native to Wisconsin," Pratt said. "Many of them were
likely carried here in the ballast water of ships, and
that may be the case for the tubenose goby."
The fish is about one-and-three-quarters inches long
and less than a year old. Biologists don't know whether
the single specimen is the result of natural reproduction
within the harbor or was an individual transported as
a very young fish this summer directly from the lower
Great Lakes.
Michigan biologists have found that tubenose goby
populations grew after their initial discovery but today
are still considered a rare species in the St. Clair
River area.
Their population pattern is different from that of
the exotic round goby, which was discovered in Lake
St. Clair during the same time period. The round goby
has expanded its range to all five of the Great Lakes,
developing abundant populations at some locations. Biologists
anticipate that the round goby may have serious impacts
on native fish communities.
Biologists are struggling to control a variety of
exotic species that have invaded the Great Lakes. Since
1986, public and scientific attention has been focused
on another aquatic invader in the Great Lakes, the zebra
mussel. These tiny striped mussels who clog water intake
pipes and crowd out native species are relative newcomers
in a long history of invaders, from rainbow smelt, alewife,
and lamprey to the recently introduced ruffe and spiny
water flea.
Gobies are considered undesirable because they can
compete with native fishes for habitat and change the
balance of the ecosystem. They are already causing problems
for other bottom-dwelling Great Lakes natives, especially
sculpins. Gobies eat fish eggs and young, take over
optimal habitat, spawn multiple times a season, and
can survive poor water-quality conditions.
On the positive side, round gobies eat large quantities
of zebra mussels, which are causing an increasingly
large number of problems because of their huge reproductive
output.
Pratt and other fisheries biologists don't know what
effects the tubenose goby will have on the ecosystem,
but they suspect the impacts won't be as severe as those
caused by the round goby.
Noting that ecological impacts can vary substantially
from area to area, Pratt said, "It's too early to speculate
the potential impacts of this new fish in Wisconsin."
