All in moderation: crayfish populations are affected by precipitation-driven habitat availability and water quality in a non-perennial stream.

Species conservation requires an understanding of the abiotic factors driving animal-environmental relationships, especially in dynamic ecosystems like non-perennial streams. Although crayfish are one of the most threatened groups of freshwater animals and are vulnerable to climate change and ecosystem degradation, data are limited for many species. Here, we evaluated crayfish-environment relationships for the Ozark Crayfish (Faxonius ozarkae), a species commonly found in Ozark Highland streams of Arkansas and Missouri. Our objectives were to: (1) evaluate the influence of spatial position, precipitation, and local physicochemical factors on crayfish density and biomass in isolated pools over a 3-year period and (2) assess pattern consistency between age groups (juveniles and age 1 +) and over time (annually and seasonally). We found few age-specific differences in crayfish density and biomass. When evaluating spatial differences, juvenile crayfish density and biomass were generally greater in upstream pools closer to perennial surface flow, while age 1 + density and biomass did not differ between stream segments. Crayfish density and biomass differed temporally, probably because of difference in precipitation, with density and biomass being greatest in a moderately wet year (2010) and lowest in years with above (2009) and below (2011) average precipitation for both age groups. Differences in crayfish density and biomass were mostly related to local habitat (i.e., pool volume, proportion of gravel substrates, substrate diversity) and water quality (i.e., pH, dissolved oxygen, conductivity) metrics. Our study adds to the growing understanding of species-environment relationships in lotic ecosystems, which will be necessary for furthering the conservation of aquatic species in non-perennial streams that are predicted to become more abundant and hydrologic variability. [ABSTRACT FROM AUTHOR]