CRITICAL-CURRENT SPEEDS FOR YOUNG GULF-COAST WALLEYES

We evaluated critical current speeds (CCS, cm/s) for young Gulf (of Me xico) Coast walleyes Stizostedion vitreum and compared the results to field determinations of water velocity under different flood condition s in Luxapalila Creek, Mississippi, which supports a small population of this species. Critical current speeds for actively feeding walleyes ranged from 8 to 74 cm/s, and were related to fish standard length (S L, mm) by log(10)(CCS) = -0.231 + 0.927.log(10)(SL), for which P < 0.0 001, r(2) = 0.67, and N = 83. Mean current velocities in Luxapalila Cr eek between May and June ranged from 20 to 45 cm/s. Means were higher than the CCS for a young walleye at that time, but velocities were spa tially variable. Persistance of walleyes in Luxapalila Creek and simil ar streams probably depends on the availability of instream structures that locally reduce current speed. Removal of such structures or chan nelization of such streams could compromise the survival of a genetica lly unique southern population of walleye.