Fish community composition detected using traditional fishing and eDNA in Dianchi Lake, Southwest China

Dianchi Lake is a eutrophic lake in Yunnan, China with many endangered or extinct native fish species. We sought to explore the fish community using traditional netting and trapping methods and, for the critically endangered golden-line barbel Sinocyclocheilus grahami, environmental DNA (eDNA) to detect its presence and distribution in the lake. Using traditional netting and trapping methods, we found that the fish community has been almost completely converted to non-native species (~ 97% of abundance). Loss of native fishes was serious, with ~ 77% of historical species not detected. We designed sensitive species-specific primers for the mitochondrial COI gene specific to S. grahami and sampled eDNA throughout the lake. While only two individuals of S. grahami were caught using traditional methods, eDNA analysis revealed its presence across the central and southern regions of the lake. While it is unclear if the fish detected represent a recovering population or recently stocked individuals, occurrence records for the fish were inversely related to regions of the lake that suffered serious cyanobacteria blooms. This study highlights the sensitivity and utility of eDNA for non-destructively detecting presence of an endangered fish species.