MINNESOTA STATEWIDE MUSSEL (BIVALVIA: UNIONIDAE) SURVEY.

Daniel E. Kelner1, Rick A. Hart2, and Mike Davis3.  
Minnesota Department of Natural Resources, Division of Ecological Services, 1St. Paul, MN
55155  2Brainerd, MN 56401  3Lake City, MN 55981.

Freshwater mussels are one of the most imperiled groups of animals in North America, yet prior
to 1999 we knew their status in relatively few of Minnesota's many river systems.  To fill this
information gap, we initiated the first statewide freshwater mussel survey in July of 1999.  A
qualitative sampling design was developed using timed searches which allows us to rapidly; 1)
define the distribution of species, 2) locate rare species, 3) compare the present and historic
fauna, and 4) determine species richness, abundance, and some limited population demographics. 
Two survey crews targeted two-person hrs./site with the intent of maximizing our ability to
sample many sites over a large geographical area.  Sample sites were selected by identifying
access points (e.g., canoe landings, bridge crossings, etc.) along each river and its tributaries and
spaced no more than 3 km apart.  We also contacted local resource agency personnel and
landowners about potential mussel communities and conducted cursory investigations via brail
and/or bank searches.  During 1999 and 2000, we spent over 1,000 hours searching for mussels at
686 sites in 25 rivers, 64 tributaries, and 7 lakes.  To date, mussel surveys in two drainage basins
of the Mississippi River; the Missouri and St. Croix, are complete.  Surveys have been nearly
completed in tributaries of the Lower Mississippi River Basin (below St. Anthony Falls at
Minneapolis including those which enter the Mississippi River below the Minnesota/Iowa
border), and partially completed in the Minnesota and Upper Mississippi (above St. Anthony
Falls) River Basins, and Pools 1, 2, and 3 of the Mississippi River proper.  Survey work in the
southern one-third of the state (Missouri, Minnesota, and Lower Mississippi River Basins) shows
that most streams no longer support their historic complement of mussel species.  This loss of
species is probably due to poor water quality and habitat degradation.  In contrast, tributaries of
the St. Croix River support healthy mussel communities of up to 25 live species, indicating
sustained quality of the system.  The high quality habitats in the St. Croix River Basin are
probably the result of less intensive agricultural and urban developments than are found in other
drainage basins throughout Minnesota.  The mussel fauna in Pools 1, 2, and 3 of the Mississippi
River, once decimated by pollution, appears to be re-establishing itself following improved water
quality conditions over the past 25 years.  Twenty-seven mussel species, most of which were
represented by young individuals, were found inhabiting this reach of the Mississippi River. 
Included in the assemblage were several Minnesota state listed species, a few of which have not
recently been reported either in the state or in this reach.  The data we collect are compatible with
Geographic Information Systems and managed by the Minnesota DNR's Natural Heritage and
Nongame Research Program.  Ultimately, the data will be used to avoid or minimize impacts
from development projects, measure the success of watershed management projects, assign legal
conservation status to mussel species, and integrated into the conservation planning process for
mussels in Minnesota. 

Key words:  Unionid, freshwater mussel, Minnesota, statewide survey, Mississippi River
tributaries