Abstract

Our study showed subtle differences in daytime macrohabitat use among three crayfish species, and between young-of-year and adult crayfish in two Missouri Ozark streams. We used a 1 m² quadrat sampler and a stratified sampling design to measure densities (number C m^-2) of Orconectes luteus, O. ozarkae and O. punctimanus in Jacks Fork River, and O. luteus and O. punctimanus in Big Piney River, during fall (1991-1993) and summer (1994-1998). Sampling effort was stratified among five macrohabitats: riffles, runs, pools, backwater/forewaters, and emergent vegetation (Justicia americana) patches. Crayfish (species and ages combined) densities throughout our streams were relatively high, but were highest in “slow-water” macrohabitats (vegetation patches, backwater/forewaters, pools) in both rivers and seasons. We observed few major seasonal shifts in macrohabitat use. Orconectes luteus was the most common species in both rivers; and although it showed density differences among macrohabitats, it appeared to be more of a generalist than the other species. Orconectes punctimanus was the least common species and appeared to be the most specialized with regard to macrohabitat use. Our data suggest that a variety of habitat types are important to maintaining the diversity and high crayfish biomass in Ozark streams.

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