Gravel Bar Trawling Project

woman releasing fish into water

Freshwater fisheries biologists study populations of six gravel-obligate Species of Greatest Conservation Need (SGCN) in northwest Florida rivers. While these fishes are occasionally encountered in Florida’s standardized electrofishing sampling, catch rates are too low to provide valid inferences about these populations. By using a new approach, the Siamese trawl, biologists have captured all six target species including the crystal darter, saddleback darter, pallid chub, southern logperch, river redhorse and Gulf sturgeon. In addition to the application of new sampling methods, researchers discovered that catch rates for many of the target species are significantly higher when sampled at night versus the day. Pallid chub and saddleback darters were common in the trawl surveys, where crystal darters and southern logperch were infrequent.  Two young of the year and one adult Gulf sturgeon were encountered. The river redhorse was previously thought to be extirpated from Florida rivers, as it had not been captured since 1976, but was collected in December 2017 by researchers during night sampling. These preliminary results are encouraging, and future sampling will be conducted with the goal of characterizing the current population status and distribution of the target SGCN species.