The influence of lake attributes and predatory bass on the distribution of northern crayfish (Orconectes virilis) in central New Hampshire

Abstract

Introduced species influence the dynamics and structure of freshwater systems; understanding the variables that shape introduced species’ distributions can aid in anticipating their spread. We examined multiple factors that may influence the distribution of northern crayfish (Orconectes virilis (Hagen, 1870)), an introduced species, in New Hampshire, USA. Sampling occurred July to August 2010 in 20 lakes. We tested catch per unit effort (CPUE) and body size of crayfish against lake trophic status, size, depth, and shoreline development, as well as substrate type. We also compared CPUE and body size in the presence or absence of known predators, smallmouth bass (Micropterus dolomieu Lacepède, 1802) and largemouth bass (Micropterus salmoides (Lacepède, 1802)). Crayfish body size was not strongly associated with any tested variables, nor were there significant correlations between lake-level parameters and CPUE. CPUE increased with rocky substrates and decreased with macrophyte cover. We also found significantly lower CPUE in lakes with bass predators; this could be due to consumptive effects directly lowering crayfish abundance, nonconsumptive effects of bass on crayfish behavior, or both. Our work provides a baseline for future surveys examining northern crayfish or bass expansion in New Hampshire and highlights a variable that could be important as this crayfish colonizes additional locations outside its native range.