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Winged
Mapleleaf Mussel Restoration
 The
winged mapleleaf mussel is a federally listed endangered
species that has received considerable management attention
in recent years. Once found throughout many Midwestern
rivers, only three known populations exist, one of which
is in a 10-mile stretch of the St. Croix National Scenic
Riverway that borders Minnesota and Wisconsin. This
population is at risk from zebra mussel infestation,
the effects of variable water releases at an upstream
hydro power dam, and an incomplete knowledge of its
life history. Among the recognized factors that are
limiting the recovery of this mussel is the lack of
data regarding which species of fish can serve as hosts
for its parasitic glochidia (mussel larvae, photo here
and here,
courtesy of
Sheri Greseth, USGS). Since 1997, a team of biologists
working at the University of Minnesota (UMN) has conducted
research to identify potential host fish for this endangered
mussel. Beginning in 2001, Department of the Interior
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Fish
holding tanks for glochidia carrying hosts.
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colleagues
working in western Wisconsin at the Fish and Wildlife
Service's La Crosse Fishery Resources Office and Genoa
National Fish Hatchery, the National Park Service's St.
Croix National Scenic Riverway in St. Croix Falls, and
the Geological Survey's Upper Midwest Environmental Sciences
Center (UMESC) in La Crosse joined other team members
in cooperative annual efforts to expand and accelerate
the laboratory host fish identification program by making
use of the well-equipped aquatic research facilities available
at the UMESC.
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Inspecting
catfish gills for glochidia.
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Prior to
2003, more than 60 species of fish comprising 14 taxonomic
families had been investigated as potential host fish
for winged mapleleaf glochidia. These early efforts achieved
very limited success with only certain catfish species
(Family Ictaluridae) because the long-term tests were
often beset by problems (e.g., fish mortality) that yielded
inconclusive results. These tests were also limited by
the ability of divers to find sufficient numbers of gravid
female winged mapleleaf in the fall to provide the necessary
glochidia for testing. In the summer of 2003 however,
an interagency dive team stockpiled adult winged mapleleaf
in the St. Croix River into small aggregations that were
placed near one another to increase chances for successful
reproduction. Divers returned early in the fall and collected
several gravid females that later released large numbers
of viable glochidia for testing. These glochidia were
used to
infest the gills of four Ictalurid species
(blue catfish, channel catfish, flathead catfish, and
slender madtom) in similar temperature-controlled tests
that were initiated in early October at both the UMESC
(19EC) and the UMN (22EC). Approximately 8 to 12 weeks
after the fish were infested, a total of about 11,000
living juvenile
winged mapleleaf mussels (photo courtesy of Sheri
Greseth, USGS) were recovered from the blue catfish and
about 9,000 juveniles were recovered from the channel
catfish.
 In mid-November,
dive team members placed most of the juveniles produced
by the blue catfish into cages that were submerged at
sites near existing mussel beds in the St. Croix River.
The survival rate of these mussels will be checked periodically.
The overwhelming test results achieved in 2003 conclusively
indicate that both blue catfish and channel catfish
are suitable hosts for glochidia of the endangered winged
mapleleaf mussel. These findings may soon be applied
to artificially propagate winged mapleleaf juveniles
for augmentation of existing populations and for reintroduction
at Mississippi River basin sites within the species'
historic range where populations have long been absent.
Guide
to Fresh Water Mussels.
Freshwater
Mussels of the Upper Mississippi River System
The point
of contact for this project is:
Mark_Steingraeber@fws.gov
(608) 783-8436
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