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ZEBRA MUSSEL DISTRIBUTION UPDATE July 1995
Over
the past 12 months zebra mussels (Dreissena polymorpha) were still breaking
new ground in North America. The most noticable spread has been the infestation
of many smaller lakes in close proximity to the Great Lakes. A total of 54 lakes
have had reports of zebra mussel veliger or adult observations. Large rivers already
infested continue to be of concern. Numbers of zebra mussels still appear to be
on the rise in the lower Mississippi River, especially in Louisiana, and in the
lower Ohio River. The descriptions below give the range and represent the most
significant new information of zebra mussel sightings in the major hydrologic
units of the United States. While population levels may have fluctuated in recent
years, all former established zebra mussel colonies have continued to persist.
Zebra mussels have infested virtually every lock and dam
in the upper Mississippi River as well as several power generation plants. No
sightings were reported from new areas in the upper Mississippi River drainage
during the past year. However, the Corps of Engineers report increased densities
at the previous sites in December 1994. The Illinois River showed decreases in
zebra mussel biomass measured at four sites last October. Biologists from the
Illinois Natural History Survey attributed the decrease to poor water quality.
In Minnesota, several boats pulled from the Minnesota and St. Croix rivers had
zebra mussels attached to the hulls. However, neither river is considered by the
Minnesota DNR to be infested at this time. Zebra
mussels first made an appearance in the lower Mississippi River in 1992. In 1993,
zebra mussels were found in Bayou Teche about one mile from its confluence with
the Atchafalaya River. This year they were found in Bayou Courtableau, part of
the Atchafalaya River Basin in Louisiana. The Louisiana Sea Grant and the U.S.
Fish and Wildlife Service confirmed that several power stations and waterworks
plants in and near New Orleans have reported zebra mussels at their facilities
. The southern-most sighting was at Venice, Louisiana, Mississippi River Mile
10. There were no significant changes
this year in the distribution of zebra mussels in this drainage. In 1992, small
numbers of zebra mussels were observed at a majority of lock and dams on the Arkansas
River. The farthest point west for zebra mussels in the Arkansas River continues
to be in eastern Oklahoma at Webbers Falls Lock and Dam. In the Verdigris River,
a tributary of the Arkansas River in eastern Oklahoma, zebra mussels were found
at River Mile 6.4 in 1993 and River Mile 26.6 in 1994. Back
in 1993, many new populations of zebra mussels were reported from West Virginia
in the upper reaches of the Ohio. Zebra mussels moved into the headwaters of the
Ohio River in Pennsylvania at Emsworth Lock and Dam, just west of Pittsburgh in
the latter part of 1994 and early in 1995. The Corps of Engineers found zebra
mussels in the Allegheny River at Lock 4, near Natrona, and Lock 7, near Kittanning,
Pennsylvania. Zebra mussels were also found in the Monongahela River at Lock and
Dam No. 2, near Braddock, Pennsylvania. As for the lower Ohio River, several reports
from different sources concur that zebra mussels are persisting in increasing
numbers there. In the mid-Atlantic drainage,
zebra mussels continue to inhabit the Mohawk River and the Hudson River from Albany
to Haverstraw, New York. In 1994, the Vermont DEC reported zebra mussels from
several locations in the middle and upper portions of Lake Champlain. Zebra mussel
colonies had been previously found only in the lower portion of the lake where
populations are reported as dense in 1995. The
most significant change in the spread of zebra mussel has been in the inland lakes
of the Great Lakes states, especially Michigan. In 1993 there were 10 inland Michigan
lakes with zebra mussels. As of July 1995, there are 29 inland lakes in Michigan
where zebra mussels have been observed. The other Great Lakes states that reported
zebra mussels in inland lakes are Illinois, Indiana, New York, Ohio, and Wisconsin.
The Cumberland River continues to support
zebra mussels. Nashville is the farthest upstream sighting we have recorded. In
the past year, the Tennessee Valley Authority reported finding veligers at all
monitoring stations downstream from River Mile 260 in the Tennessee River. Moderate
numbers of adult zebra mussels have been found at all nine Tennessee River Locks
up to River Mile 602, near Knoxville. Since
the initial finding of zebra mussels on a boat at a California agricultural inspection
station in 1993, five additional boats with zebra m ussels attached to their hulls
have been detected at three different inspection stations. The second finding
of zebra mussels ocurred in Califor nia last November. Forty specimens were removed
from a boat on a flatbed trailer being shipped from Toledo, Ohio to San Diego.
Their condition was listed as "live" at the time of collection according to the
California Department of Water Resources. The third occurrence took place in March
of this year when "live" adults were found in the starboard intake of a 40-ft
yacht. The origin of this boat was Michigan, and like the last boat, its destination
was San Diego. These first three finds were all reported from the Needles Inspection
Station. The next occurrence was reported from the Yermo Inspection Station in
May 1995. This boat also came from Michigan but had been out of the water for
over a year. The most recent two boats were detected at the Truckee Inspection
Station in June 1995. The origin of both boats was Michigan and both had been
drydocked for long periods so there were no live mussels. Given these instances,
it would appear that overland transport of zebra mussels on or in boats from thousands
of miles away poses a real threat to uninfested waters.
New technology is being used to distribute this information. Although custom
data queries and products can be provided by our staff, computer network and dial-up
services are being developed to facilitate data transfer. Currently, a World Wide
Web server http://nas.er.usgs.gov is available to anyone with
access to Internet. This server provides real-time, spatial and logical data queries.
This is by no means all the information on confirmed zebra mussel sightings but
we feel we have received accurate information through a network of contacts to
sufficiently represent the distribution. We welcome your input
with information about new sightings.
For further information contact: Amy Benson U.S.
Geological SurveyCenter for Aquatic Resource Studies7920
NW 71st Street Gainesville, FL 32653Comm.:
352-264-3477 Fax: 352-378-4956
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