The Importance Of Host Fish In Long Range Transport Of Unionids In Large Rivers

Freshwater mussels (Family: Unionidae) are the most imperiled faunal group in North America, yet little is known about factors that influence their distribution in rivers and lakes - especially over large geographic areas. They have a unique life cycle that includes an obligate parasite stage on fish. Throughout their life spans, long range or upstream transport is principally accomplished during the parasitic stage. This brief parasitic phase has lasting effects on adult mussel ecology - particularly in influencing their distribution. The movement of host fish occurs on large scales (e.g., >100m) and both their distribution and abundance likely contribute to the spatial patterns of mussel communities. I estimated the home ranges of host fish to determine the potential movement of larval freshwater mussels and used empirical data to predict the potential ecological consequences of host fish and freshwater mussel spatial relations in the Upper Mississippi River (UMR). Also, the degree of connectivity provided by fish hosts among mussel sites was quantified and I determined if connectivity is correlated to mussel bed condition in the UMR. I show that ecosystem size and shape influence home ranges of fish and home range is not based solely on body size-home range relationships (i.e., allometry). I show that the spatial distribution of mussels and their host fish are highly clustered, suggesting that ecological processes may be occurring on a landscape scale and should be considered into the management plans for these imperiled species. Also, high mussel species richness correlates with high host fish species richness and that most mussel communities in the UMR are located within the estimated home ranges of their host fish. Host fish were directly connected to mussel communities given that the distribution of home ranges of host fish consistently overlapped with the distribution of mussel communities. Mussel community condition was highly correlated with functional connectivity provided by host fish among mussel communities in the UMR. This presents a spatially realistic look at the potential of long range transport that host fish provide mussels.