Crayfish Growth in Lake Tahoe: Effects of Habitat Variation

Abstract

The natural history and ecology of the freshwater crayfish Pacifastacus leniusculus was investigated in Lake Tahoe for 1 yr. Growth of individual groups varied between three different transects (I, II, and III). The mean size of carapace of adult crayfish trapped on Transects II and III was greater than those trapped at Transect 1. Linear regression analyses of premolt–postmolt carapace length revealed similar differences. At the onset of sexual maturity females from Transect I were smaller than those from either Transect II or III.Examination of physical and biological parameters in the benthic habitat revealed that food availability, amount of shallow water, and size and area of stone cover influenced the number and size of adult crayfish on each transect. Greater food availability and more extensive stone cover on the lake bottom attracted higher numbers of crayfish to Transect I. The result was overcrowding and competition for food and larger stone cover for larger adults. The effect was a slower growth rate of crayfish on Transect I compared with animals on either of the other transects.