Rare or Rarely Sampled? Electrofishing and Environmental DNA Surveys of the Imperilled Freckled Darter Percina lenticula

Abstract

The southeastern (SE) United States is a biodiversity hotspot for freshwater fishes, with the darters (Percidae) comprising a large portion of the diversity. The endemic Freckled Darter Percina lenticula was once found across numerous drainages in the SE United States; however, human modifications to waterways have caused local declines to the extent that the species is ‘critically imperilled’ in parts of its range. The putative habitats of P. lenticula pose challenges for traditional sampling techniques, contributing to a paucity of data related to its status, distribution, and abundance across much of its range. This study assessed the occurrence and distribution of P. lenticula in the Pearl and Pascagoula River drainages using electrofishing and eDNA techniques. In the Pascagoula drainage, P. lenticula appears to have a broad distribution, being found via both survey approaches in all tributaries sampled. P. lenticula was detected in the Pearl River drainage for the first time since 1977 via eDNA surveys, but none were found in electrofishing surveys. This indicates the continued survival of P. lenticula in the Pearl River drainage, but they may occur in more localised areas and/or in lower abundances than in the Pascagoula River. Additional spatially comprehensive eDNA surveys in the Pearl River drainage would support future electrofishing surveys to definitively identify locations of remaining populations and estimate abundance(s). Similar surveys should occur across the SE United States to support an updated assessment of the conservation status of P. lenticula, shedding light on whether (and where) the species is rare, or rarely sampled.