Habitat Partitioning by a Lotic Crayfish Community of the Ozark Plateau with Emphasis on the Imperiled Mammoth Spring Crayfish

Flinders, C. and D. Magoulick

The American Fisheries Society Endangered Species Committee recently listed the Mammoth Spring crayfish (Orconectes marchandi) as endangered, as populations were known in only two streams of Missouri and Arkansas and little was known of the distribution, life history, and ecological factors affecting O. marchandi populations. As part of a study to determine the status of the Mammoth Spring crayfish, we examined habitat partitioning and the importance of physical characteristics in
determining crayfish community structure at two sites each on the Warm Fork River, Missouri and Janes Creek, Arkansas.  Twenty replicate quadrat samples were collected from six macrohabitat types (riffle, run, pool, stream margin, vegetated areas, and backwater) at each site and the physical characteristics from each sample were quantified. Four crayfish species were collected (O. marchandi, O. ozarkae, O. punctimanus, and Cambarus hubbsi) and divided into two size classes for examination by CCA. Species-size class composition differed significantly by stream, site, and macrohabitat type. Densities of O. marchandi were similar in both streams with small crayfish positively associated with stream margin and backwater habitats and large specimens positively associated with pools in both streams, and with runs in Janes Creek. Cambarus hubbsi and O. punctimanus were significantly more abundant in the Warm Fork than in Janes Creek with both large and small C. hubbsi found primarily in the faster riffles and runs and small O. punctimanus in vegetated habitats. Orconectes ozarkae was less abundant in the Warm Fork than in Janes creek with small crayfish showing a positive association with vegetated habitats and large crayfish with runs. Separate analyses performed on each stream ordinating environmental variables with relative crayfish abundance indicated that measured environmental variables were responsible for a significant amount of spatial variation in crayfish density. In both streams, vegetation, mean current velocity, water depth, and percent canopy cover were the most important factors in explaining differential crayfish density. Crayfish density was positively associated with vegetated areas and negatively associated with water depth, current velocity, and absence of canopy cover.  These data show habitat partitioning in this lotic crayfish community and demonstrate the importance of physical variables in explaining crayfish community structure with stream margin, backwater, and pool macrohabitats appearing particularly important to the imperiled Mammoth Spring crayfish.

Copyright © 1999
Texas Chapter of the American Fisheries Society
Last modified: 01/07/09 06:45:17 AM