Can fish help in unionid recovery? Predicting unionid populations based on fish distribution in Ontario rivers

In order for freshwater mussels (Family: Unionidae) to survive, their distribution must spatially and temporally overlap with their hosts. Spatial patterns in unionid communities and their host fish were examined to determine the degree of biological connectivity among mussel beds that host fish provide. I considered the spatial patterns of host fish and non-host fish by collecting fish in ~ 2.5 km reaches of three rivers in southwestern Ontario (Sydenham, Thames, and Ausable) in areas where spatially explicit unionid data was available from excavation surveys. I show how predictive surfaces (e.g., Inverse Distance Weighting) can be used to determine 1) the connectivity between unionid communities, 2) target recovery areas and 3) pinpoint fish species to host test. Host communities for Endangered unionid species (n=5) are compared and show lower biological connectivity provided by host fish between known mussel locations than from the biological connectivity provided by hosts to more common species (n=2) of freshwater mussels. However, >40% of all fish collected show evidence of unionid encystment confirming probable hosts that have yet to be tested.  I will highlight how recovery habitat can be chosen based on the host-parasite relationships of unionids.