Population and conservation biology of the threatened leopard darter

Scope and method of study. Abundance of leopard darters was determined in Big Eagle Creek and West Fork Glover River in southeastern Oklahoma using a mark-recapture (Schnabel) technique and geographic information systems (GIS) technology. Differences in abundance among streams and among years were related to stream geomorphology and hydrology. Swimming performance in four water velocities (0-25 cm/s) was measured in a laboratory flow-through apparatus, and the results were compared to velocities measured in culverts under road crossings. A nonpoint source model and GIS were used to estimate sediment yields associated with silviculture and relate yields to quality of leopard darter habitat.; Findings and conclusions. Abundances of leopard darters in the two streams (35,000-98,000) were considerably higher than previous estimates. Higher habitat diversity and complementation and lower dominance in Big Eagle Creek likely influenced the higher abundance of leopard darters observed in that stream. In addition, a drought in fall 1995 and unusually low flows in spring 1996 limited spawning success, resulting an a decline in abundance from 1995 to 1996. Swimming activity increased at 25 cm/s, but there was evidence that it decreased above 40 cm/s. Mean water velocities exceeded 40 cm/s more often in corrugated pipe than in open-box culverts, indicating that culverts, particularly corrugated pipes, could be potential barriers to the migration and dispersal of leopard darters. Sediment yields increased downstream and were three times higher in West Fork Glover River This was attributed to a fivefold difference in the area of clearcut forest in the West Fork Glover River.; This research showed that leopard darters are more abundant than previously believed. Abundance and survival of the species, however, are influenced by environmental and anthropogenic factors. In addition, new methodological techniques for estimating abundance and examining anthropogenic influences were developed. Such information has implications for future research on the management and recovery of the species, particularly identifying suitable sites for re-establishment of previously extirpated populations.