Exotic spiny waterflea found infesting
By Steve Foss
The Timberjay News
The DNR and Minnesota Sea Grant Program have confirmed
that a very small exotic - which could become a big problem
- has been found in Lake Saganaga in the BWCAW along the
Biologists identified the harmful exotic spiny waterflea
in Saganaga after studying samples collected by a summer
Saganaga, located at the end of the Gunflint Trail in
northern Cook County, is the third inland water body in
the state to be infested with the tiny exotic zooplankton,
which may disrupt local food chains and outcompete native
The spiny waterflea takes its name from the barbs on
a long tail filament, which can catch on fishing lines,
aquatic vegetation and downrigger cables. These tiny barbs
can also stop small fish from eating this animal.
The infestation danger is in transporting the adult females
and the eggs, which cling to lines and cables and look
like gelatinous or cottony strings. While adult fleas
taken from water die quickly, the eggs can dry out completely
and remain viable. Once introduced again to water, they
reconstitute and hatch into female fleas. The females,
which reproduce asexually, will form their own eggs and
infest the new lake, said Doug Jensen, exotic species
specialist with Sea Grant.
How it happened
The waterflea is native to cold climates in eastern Europe
and western Russia and Siberia, and made its way into
Lake Ontario in 1982 through the shipping industry, according
to Jensen. It likely spread through the great lakes in
the same way as several other exotics, when ships picked
up infested ballast water and discharged it in other lakes.
Shortly after its discovery in Lake Superior, it was
also found in Island and Fish lakes, about 20 miles northwest
of Duluth and popular destinations for anglers who also
fish Lake Superior.
Jensen believes the flea came to Saganaga by hitchhiking
on fishing equipment of Lake Superior anglers from the
Grand Marais area.
Biologists hope to monitor the lake to see if the tiny
(less than ½ inch long) exotic affects fish populations
or other aquatic life in the lake.
Whatís the problem?
There is strong, but not conclusive, evidence the species
is damaging to local food chains.
In southern Lake Michigan, infestation was followed by
the loss of several small species of plankton. In Harp
Lake in southern Ontario, no small zooplankton species
remain after infestation.
Smaller fish canít eat spiny waterfleas, so large numbers
could impact the food chain, according to Gary Montz,
DNR aquatic invertebrate biologist. And Jensen said that
the loss of smaller zooplankton species may create a bottleneck
in the food chain, since some fish depend on small zooplankton.
However, larger fish can eat the water flea, so the impacts
from the infestation are difficult to predict.
Biologists arenít ready to say waterfleas have directly
caused the changes in lakes Michigan and Harp - though
they suspect it - because ecosystems are complex, and
their components can vary widely because of other factors,
How to stop it
Montz says it is important that people visiting infested
waters take time to avoid spreading this species.
Clumps of spiny waterflea can become entangled in fishing
lines, downrigger cable or other gear. Montz said it is
important to clean off any equipment that may have spiny
waterflea attached to prevent moving eggs.
In Minnesota, the spiny water flea is a regulated exotic
species and may not be introduced in state waters. State
regulations require that anglers drain all lake water
from their boats, including live wells, bait buckets and
bilge areas before leaving the access of waters infested
with spiny waterfleas.
Signs reminding anglers and boaters of these preventive
actions will be posted at public access areas, Montz said.
Itís important not to lose heart and believe the war
against invaders is being lost, Jensen said.
"Weíre actually protecting these lakes," he
said. "Less than 1 percent of Minnesotaís 15,000
lakes are infested."
Jensen said that, once Minnesota boaters are aware of
a problem with exotics, they respond quickly and in large
More than 95 percent of the stateís boaters are taking
steps at accesses to protect against zebra mussel and
Eurasian milfoil infestation, which Jensen said has dramatically
decreased the rate of milfoil infestation and probably
accounts for the fact the Lake Zumbro, near Rochester,
is the only inland lake known to contain the mussels.
"But they need to know what to look for," he
said. "Our charge is to get the identification info
out there and tell people how to take action."
The agencies have worked together to produce spiny waterflea
identification cards similar to those warning against,
milfoil, zebra mussels and rusty crayfish.
Not only do state wildlife agencies have the cards available,
but bait shops, resorts and convenience stores that sell
licenses and bait can get them for free by contacting
either agency. Individuals can get single cards free by
contacting the agencies.
Contact the DNR Information Center at (888) MINNDNR (646-6367)
and the Minnesota Sea Grant Program at (218) 726-8712.
More information on the species is available through Sea
Grantís Web site at www.seagrant.mnu.edu.