Distribution and habitat of unionid mussels and invasive sea lamprey larvae in the Paw Paw River, a tributary of Lake Michigan

Abstract

Summary1. Lampricides are commonly used to control invasive sea lampreys (Petromyzon marinus) in tributaries around the Great Lakes (U.S.A.) by targeting their larvae (ammocoetes). As lampricides have sublethal effects on unionids, this study investigated unionid and ammocoete distribution and habitat use to aid in refining lampricide applications.2. Habitat and unionid surveys were conducted in the Paw Paw River, in south‐west Michigan (U.S.A.). Unionids were predominately present in the upper main stem, while the probability of ammocoete presence was highest in the tributaries and lower main stem.3. Generalised linear models revealed median particle size and gradient to be effective predictors of unionid distributions, while distance to sea lamprey spawning habitat and bank stability were effective predictors of ammocoete distributions.4. Minimal overlap of unionid and ammocoete distributions suggests that refinement of lampricide treatment in the Paw Paw River is possible. We propose redefining the extent of the treatment unit so that only areas with a high probability of ammocoete presence and a low probability of unionid presence are treated with lampricide. This could result in reducing treatment costs and minimising threats to unionid conservation, while not jeopardising the success of lampricide treatment programmes.