Zebra mussel [Dreissena polymorpha (Pallas)] colonization of rusty crayfish [Orconectes rusticus (Girard)] in Green Bay, Lake Michigan

In August 1995 six rusty crayfish (Orconectes, rusticus) colonized with zeb ra mussels (Dreissena polymorpha) were captured in small-meshed fyke-nets s et as part of a fish sampling effort at Peter's Marsh and Long-Tail Point W estland in lower Green Bay. The number of mussels per crayfish ranged from 16 to 431 and the length of the zebra mussels ranged from 1.2 to 12.0 mm wi th a mean of 3.6 mm. Mussels colonized virtually all areas of the crayfish bodies but the chelate, telson and uropods and thorax were most heavily col onized. Although it is possible that zebra mussels may have positive effect s on crayfish populations through associated effects on water clarity, auto troph and invertebrate production, we are concerned that energetic costs or physical constraints caused by attached zebra mussels mal be detrimental t o crayfish in the Great Lakes.