Abstract

From 1989 to 1991, we trapped crayfish throughout the St Louis River Basin to determine abundance patterns and habitat preferences. Orconectes propinquus, previously unreported from this basin, was the dominant crayfish in the Cloquet River, Stoney Brook, Artichoke River, and nearby portions of the St Louis River. In 1991, we surveyed six reaches on the Cloquet River and one on Stoney Brook to determine habitat use by this crayfish. A diver counted and measured crayfish and described substratum conditions within 0.09 m² frames. Water velocity and other habitat parameters were also assessed. Average abundance was 21.6 crayfish per m² at the Stoney Brook site and ranged from 2.8 to 23.8 crayfish per m² in Cloquet River reaches. Chi-square analysis of crayfish presence by particle size showed signifi­cantly non random distributions. YOY (< 1.6 cm CL) occurred at higher than expected frequencies on large gravel/small cobble and less frequently than expected on silt/ sand. Medium (1.6-2.8 cm CL) and large (> 2.8 cm CL) crayfish avoided silt/sand substrata entirely and were more frequent than expected on large cobbles and boulders. Multiple regression analyses showed water velocity and embeddedness were important factors for describing the distribution of all size classes within these streams. Water depth was also an important factor for medium and YOY sizes. Spread of Orconectes propinquus into headwaters of this basin appears to be limited by dams, lack of suitable rocky cover, and dispersal time.

Supplemental Documents

• There are no supplementary documents for this article

Cited By

Citations: