By Kayla Smith and Chelsea Myles-McBurney
Our freshwater fisheries biologists in the panhandle are working on an imperiled species trawl survey in the Escambia River. Crystal darter (Crystallaria asprella), Gulf sturgeon (Acipenser oxyrinchus desotoi), saddleback darter (Percina vigil), pallid chub (Macrhybopsis sp. cf aestavalis), southern logperch (Percina austroperca) and river redhorse (Moxostoma carinatum) are listed as species of greatest conservation need, and are not routinely sampled during long-term fish monitoring surveys. These species share an important aspect of their life history: the use of gravel substrate is required at some point in their lifetime, making them gravel obligate species.
Prior to this project, only 11 crystal darters have been collected on the Escambia River since the 1970s. Crystal darters are known only to occur in the northern-most reaches of the Escambia River and little information exists on their distribution and habitat use. Using a mini-Missouri trawl, crystal darters and the other species mentioned above were targeted over gravel and sand bars. Since 2016, 357 trawls were conducted successfully. A total of 37 species were collected including five of the target species for the project. Although crystal darters are relatively rare, a total of 29 were collected during two years of sampling. These 29 individuals were all tagged using visual implant elastomer to determine if recapture was occurring.
Trawling was conducted both during the day and at night; however, researchers found that night trawling was much more successful at capturing crystal darters. In addition to the increase in crystal darters, researchers also captured a river redhorse, which had not been documented in the Escambia River since 1976. This individual was implanted with an acoustic tag and released. The movement of this fish will be monitored using Vemco VR-2 receivers to estimate site occupancy and assess population trend.