Relationships Between Multi-Scale Environmental and Land-Use Factors and Summer Demographics of the Northern Clearwater Crayfish, Orconectes Propinquus (Decapoda: Cambaridae)

Abstract

Crayfish are structurally important in streams as a main component in the food chain and as decomposers of organic material. They exhibit wide sensitivities to environmental disturbance and serve as response indicators of habitat degradation and anthropogenic effects. Thirty stream reaches in central Indiana were sampled to determine relationships between relative abundance, size, age, sex, and habitat associations of the Northern Clearwater Crayfish, Orconectes propinquus. Females were significantly more abundant than males (P = 0.08303). The frequency of crayfish in gravel substrate was significantly higher than that of cobble substrate (P < 0.0001). The size of crayfish in cobble substrate were significantly larger (P < 0.001) than individuals found in gravel substrates, while females were significantly larger (P = 0.013) than males in gravel substrates. Watershed variables were not significantly related to crayfish abundance. The only reach scale variable that proved to be significant (P = 0.084) was a boulder substrate score. Microhabitat variables showed a significant increase between catch-per-unit-effort (CPUE) and cobble (P = 0.083) and gravel (P = 0.099) substrates.