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fish with a bad haircut
by Marie Zhuikov
(May 1997 "Seiche" Newsletter, MN Sea Grant)
This exotic fish may look like a punk rocker, but it's really a
threespine stickleback (Gasterosteus aculeatus). While not
new to the Great Lakes, the two- to three- inch fish is somewhat
new to Lake Superior. It is showing up with more frequency, causing
some anglers to scratch their heads when it appears in their smelt
nets or on their fishing lines. So what is this fish and should
we be worried about it?
Threespine sticklebacks are commonly found off the Atlantic and
Pacific coasts of North America. Opinion is split on how they got
to the Upper Great Lakes, but biologists assume they entered through
the St. Lawrence Seaway in the ballast water discharge of ocean-going
ships, or that they traveled via natural migration through the Hudson
Bay watershed. Since 1980 they have spread to Lake Michigan and
are now found in Lake Superior.
Minnesota Sea Grant Exotic Species Information Center Coordinator,
Doug Jensen, remembers when threespine sticklebacks first appeared
locally in LTV Steel's cooling water tanks in Taconite Harbor, MN,
in 1994. "When I first confirmed the sighting, I was not very
concerned. Based on the published literature, the species appeared
to be of little threat," said Jensen. "Even after Dennis
Pratt of the Wisconsin DNR reported that he found them in the Duluth-Superior
harbor, we came to the same conclusion, "So what?" Since
then, I've become more concerned due to recent reports from southern
Lake Michigan where the infestation has rapidly grown."
Jensen is hearing stories from anglers who shore-fish there for
yellow perch that paint a bleak picture. Anglers catch threespine
sticklebacks and round gobies, but few yellow perch or native fishes.
"One time last year, 12 anglers fishing for five hours caught
about 1,000 fish made up of just round gobies and threespine sticklebacks,"
said Jensen. "Anglers report these sticklebacks are so aggressive
that they will attack a penny dropped into the water. Not even the
aggressive goby goes after the penny. If this stickleback is that
aggressive and becoming that abundant, perhaps there should be more
concern and research devoted to them."
Little is known about its biology or potential environmental impacts.
Threespine sticklebacks are easy to identify, with three spines
on the dorsal fin and large eyes. The first two spines are very
pronounced, the third is much smaller. They inhabit shores of larger
lakes. Shallow, sandy bottomed areas are their preferred habitat.
In spring, the males construct an elaborate underwater nest from
algae, sticks and plant fragments which resembles an oriole's nest.
The nest is usually attached to emergent aquatic plants, but sometimes
it is built on the bottom itself. After the female lays the eggs,
the male guards them until they hatch and then watches over the
fry until they disperse.
Threespine sticklebacks may compete with native sticklebacks for
food. They eat zooplankton, oligochaetes and chironomid midge larvae
and mosquito larvae.
The ninespine stickleback (Pungitius pungitius) is a native
stickleback common in northern Minnesota. As you can probably guess,
it features nine spines. The brook stickleback (Culaea inconstans)
usually has five spines, but the number can vary from three to seven.
If you catch what you believe is a threespine stickleback in Lake
Superior, we want to know about it. Please kill it, freeze it, and
call Doug Jensen at 218.726.8712,
or the Minnesota Department of Natural Resources Exotic Species
Program in St. Paul,1-800-766-6000 or 612.259.5100.
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