Some Ecological Notes on the Blue Color Phase of the Crayfish, Orconectes Virilis, in Two Lakes

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Ecological data on growth, population density and mortality were collected and analyzed for blue color phase variants of the crayfish populations in North Twin and South Twin Lake, Otsego County, Michigan. Crayfish were collected with baited minnow traps, growth was determined by size frequency analysis of the total catch, and mortality analyzed by use of sequential mark and recapture population estimates. The results suggest that growth is density dependent, survival between blue and normally brown color phases is not different and that the percentage of blue color phase variants in these populations does not exceed one percent of the total population. The lack of difference in mortality rates between the olive brown and blue color phases and the lack of blue crayfish in the stomachs of the fish in these lakes does not support the thesis of selective mortality on the conspicuous blue color phase.


Author Institution: Department of Zoology and School of Natural Resources, The Ohio State University, Columbus, Ohio 43210



The Ohio Journal of Science. v71 n6 (November, 1971), 363-370