Factors Influencing Crayfish Distributions in Streams

Abstract

Crayfish are important to study because they are ecosystem engineers that are often an invasive species and that are pivotal in predator-prey interactions (Townsend 2004, Olden et al. 2005). Calcium levels along with substrate size have been shown to be important factors influencing crayfish distributions in Wisconsin lakes (Capelli and Magnuson 1983). They showed two things, that lake calcium levels below 2.5 parts per million (ppm) resulted in an absence of crayfish, and that crayfish preferred larger substrates. Much is known about the physio-chemical factors impacting crayfish distributions in lakes, but less is known about factors influencing crayfish in streams. We hypothesized that crayfish distributions preferred large substrate and calcium levels of at least 2.5 ppm.