Age-specific Differences in the Distribution of Red Shiners, Notropis lutrensis, over Physicochemical Ranges

Niche breadth and overlap indices were used to compare the distributions of juvenile (<24 mm SL) and adult red shiners (Notropis lutrensis) in ranges of 10 physicochemical factors at five different times of year at a field study site in central Oklahoma. Compared to adults, juveniles at times selected higher temperatures, higher oxygen concentrations, higher pH, lower total dissolved solids, lower turbidity and more stable substrates. Compared to juveniles, adults at times occupied deeper water and locations with more shelter and more shade. The two age groups did not segregate for current speed, as both selected the slowest speeds available. Overlap between the age groups was greatest during environmental stress. Within ranges of the various factors, adults had a wider habitat breadth 15 of the 20 times that differences in breadth were meaningful. Changes in adult mean habitat breadth were more closely related to environmental change than were changes in juvenile habitat breadth.