Determining habitat characteristics of an invasive snail (Bithynia tentaculata, Linnaeus, 1758) and associated trematodes on the Upper Mississippi River

On the Upper Mississippi River, an exotic snail, the faucet snail (Bithynia tentaculata) serves as the intermediate host for three trematode parasites (Sphaeridiotrema globulus, Cyathocotyle bushiensis, Leyogonomus polyoon).  These trematodes can cause mortality in waterbirds.  Since 2002, total bird mortality is estimated at 50-60,000 birds.  This disease event further stresses avian populations already in decline.  To gain a better understanding of factors affecting Bithynia distribution, we began incorporating abiotic and biotic factors into our assessments of B. tentaculata densities, distribution, and trematode infection rate.  Based on our research, high densities of B. tentaculata appear in rocky areas with low water flow and low densities tend to occur in sandy areas with high flow.  Patch occupancy models were used to relate habitat and environmental characteristics to probability of occupancy and (or) detection while accounting for imperfect detection of faucet snails. Preliminary results indicate that variables estimated to influence the probability that a site will be occupied included whether the site was vegetated, in the impounded area, presence of filamentous algae, wild celery (Vallisneria americana), purple loosestrife (Lythrum salicaria) or coon’s tail (Ceratophyllum demersum), and average depth.  One of the key endpoints for this work is to predict how invasive hosts and parasites spread through aquatic systems which can lead towards knowledge in developing management actions used in the control of invasive species.