Diversity, distribution, and abundance of freshwater mussels in the Raisin River drainage basin, Eastern Ontario, Canada

The ecology and conservation biology of freshwater mussels (superfamily Unionoidea) has been the subject of a rapidly increasing number o f field studies over the past two decades. Among the factors explaining this level o f interest is the realizatian that freshwater mussels are among the most endangered and threatened fauna {WILLIAMS et al. 1992). North America supports the largest variety offreshwater mussels o n the planet with over 300 recognized species and subspecies belonging to either the family Unionidae or Margaritiferidae (WrLLIAMS et al. 1992). In addition, aquatic biologists and conservation biologists recognize that, especially in flowing waters, freshwater mussels can play a significant functional ro le in filtering suspended particles and recycling nutrients (e.g. VAUGHN et al. 2004 ). Moreover, the hos t fish involved in the dispersal o f mussellarvae, as well as the conservation status ofthe species, are not well known for the majority of taxa. In a separate study ofthe water quality ofthe Raisin River system, Eastern Ontario, Canada, freshwater mussels were often found in riffie zones. A more detailed sampling was subsequently conducted to determine the structure ( abundance, diversity, and distribution) ofthe mussel communities and whether this structure could be explained by environmental factors. The specific objectives were to: (l) determine the species richness and quantify mussel abundance at a range of riffie si tes, (2) investigate their spatial distribution (within tributaries and between-tributaries or main branches) in relation to stream environmental factors, (3) determine relationships with habitat characteristics and environmental factors, and finally (4) examine the relationship between mussel and fish community structure.