An evaluation of a possible technique for mitigating unionid mollusks mortality caused by zebra mussels: a case study in Douglas Lake.

Abstract

Zebra mussels (Dreissena polymorpha) have had consider ecological effects on many lakes of the Great Lakes Region, including Douglas Lake (Northern Lower Peninsula in Michigan, USA). People inhabiting the University of Michigan Biological Station of Pellston, MI, during the summer have been cleaning clams along the shores of South Fishtail Bay for five years when the opportunity arises. This study examined whether clams along South Fishtail Bay were healthier than clams from other parts of the lake, possibly because people clean these clams regularly. Clams from South and North Fishtail Bays were surveyed. The species, length, thickness, mass, and percent coverage by zebra mussels were determined for each clam found. The weight of zebra mussels attached to each clam was also determined. A 1‐tailed T‐test was used to analyze whether populations of clams differed in mass, length, or the mass of mussels each clam carried. The Lampsilis siliquoidea from South Fishtail Bay were significantly larger than those from North Fishtail Bay, but this was not the case for Ligumia recta. The lengths of both species were not significantly different between the two bays. Clams from South Fishtail Bay of both species had significantly fewer zebra mussels on them compared to clams from North Fishtail Bay. Results support the hypothesis that South Fishtail Bay has healthier clams than North Fishtail Bay. Clams from South Fishtail Bay are heavier compared to clams from North Fishtail Bay of comparable length. People cleaning the clams may contribute to this observed difference in masses, since clams are regularly cleaned on South Fishtail Bay in the summer and not so in North Fishtail Bay.