CONRAD S. TOEPFER AND WILLIAM L. FISHER, Oklahoma Cooperative Fish and Wildlife Research Unit, 404 Life Sciences West, Oklahoma State University, Stillwater, Oklahoma 74078, USA

The leopard darter is a threatened species endemic to five streams in southeastern Oklahoma and southwestern Arkansas. Migrating individuals would have to cross road culverts, so we used swimming performance as a measure of their ability to cross these barriers. Performance was evaluated in a flow-through apparatus at current velocities of 0, 5, 12, and 25 cm/s. Eight leopard darters were tested at each velocity, and their activity in terms of swimming burst length and duration was measured. Using a nested ANOVA, we found that burst length, duration, and speed (body lengths/second) were significantly different between velocities with the greatest activity at 25 cm/s. Current velocities measured at road culverts in the Mountain Fork and Glover Rivers ranged from 0 cm/s to over 2 m/s with a mean of about 70 cm/s. Our findings indicate that leopard darter swimming activity increases significantly at moderately high velocities (i.e., 25 cm/s); however, it seems improbable that leopard darters could sustain swimming or maintain their position on the bottom at extremely high velocities (i.e., > 1 m/s) that can occur in stream culverts.