U.S. Water News Online
DUBUQUE, Iowa -- The zebra mussel has improved fishing in
the Mississippi River by clearing the water, but it is hurting other
aquatic life, a biologist said.
``They are not, however, a good thing,'' fisheries biologist Scott
Gritters said. ``They are a catastrophe. They have made the river
clearer but at the expense of 44 species of freshwater mussels.''
That includes the impending extinction for the Higgins' eye
mussel, said Gritters, who spoke at a meeting to alert the public to
the small, brown mollusks' imperiled status.
Gritters, an Iowa Department of Natural Resources biologist
stationed at Guttenberg, said the filtering action of billions of
zebra mussels has helped to clarify the water of the Mississippi,
which has improved angling for some game fish species on the river.
Always rare, the Higgins' eye was on the federal endangered
species list before the recent invasion of zebra mussels.
The U.S. Fish and Wildlife Service last year took the unusual step
of placing the Higgins' eye in jeopardy status.
Zebra mussels, exotic invaders brought from Asia to the United
States in the ballast of ships, are literally paving over the
Higgins' eye mussels, said Gritters, a member of the multi-agency
Higgins' eye recovery team.
Another member of the team, U.S. Fish and Wildlife Service
biologist Gary Wege, said divers searching for Higgins' eyes last
summer had to push their entire arms through a layer of zebra mussels
to reach the actual river bed.
The East Channel of the Mississippi at Prairie du Chien, Wis., was
once known as the mother lode of mussels, Wege said.
``Between 1995 and 1999, the number of species found there went
from 30 to seven, and the overall abundance declined 98 percent.
Wege said he fears the Higgins' eye may soon be extinct.
``We are right on the edge of losing them,'' he said. ``We are not
working toward recovery at this point. We are just trying to keep
them from going extinct.''
The Higgins' eye recovery team is trying to save the species. Last
year, Wisconsin DNR biologists dove to the bottom of the Cassville
slough and found 200 living Higgins' eyes, which they cleaned and
The Wisconsin DNR also is experimenting with raising Higgins' Eye
clams in the federal hatchery at Genoa, Wis.
Return to the
U.S. Water News Archives page
Return to the U.S. Water
Use a comma to separate e-mail addresses:
Hi, I thought you might like to read this article.