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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Unionid Ecology
REACH AND LANDSCAPE-SCALE DETERMINANTS OF FRESHWATER MUSSEL (BIVALVIA: UNIONIDAE) DISTRIBUTIONS IN AN AGRICULTURAL WATERSHED OF SOUTHEASTERN MICHIGAN.
S. Kopplin and J.D. Allan. School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109-1115
We investigated the diversity and distribution of freshwater mussels in an agricultural watershed, the River Raisin in southeastern Michigan, in order to relate their distributions to within-reach and landscape-scale variables. Unionids were surveyed by timed searches in 100-m reaches at each of 40 sites, mussels were identified to species and measured, and in-stream and riparian habitat were quantified, as well as flow, water chemistry, and channel morphology. Some 21 mussel species were found overall; six sites had no living species, five sites had only one species present, and the maximum number of species per site was 12. In-stream variables, including flow stability and substrate composition, as well as off-stream variables, such as stream size, geology and land use, were found to be the most important variables affecting mussel density and distribution in the River Raisin (R2 = 0.62, p < 0.001). Previous works have focused on microhabitat or regional predictors of mussel distribution, however, this study demonstrates that a combination of both reach-scale and landscape-scale habitat variables can be useful in explaining mussel distributions. We also found a distinct spatial pattern of the mussel community, which we attribute primarily to the underlying surficial geology of the basin.
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