Environmental DNA compliments traditional sampling for monitoring fish communities in a Texas estuary

Abstract Objective Environmental DNA (eDNA) metabarcoding has become an important method for inventorying and monitoring biota in aquatic systems. The Texas Parks and Wildlife Department conducts regular fishery‐independent sampling of biotic communities using traditional sampling gears, such as gill nets and bag seines, in all of the major estuaries of adjacent to the Gulf of Mexico in Texas. Previous studies have shown that eDNA approaches can complement traditional sampling methods. Methods We compared fish community structure data in the Cedar Lakes estuary system obtained with traditional sampling gears with data obtained using eDNA sampling using a small sequence of mitochondrial 12S ribosomal RNA gene and a validated taxonomic reference file. Result For spring and fall of 2022, eDNA metabarcoding detected a larger number of species than either bag seines or gill nets. Species richness detected via eDNA in two seasons in a single year was comparable with the species richness of agency’s historical record based on traditional gears for Cedar Lakes. Conclusion Seasonal and spatial variation in species richness was similar between traditional and eDNA sampling; however, eDNA metabarcoding allowed detection of several species that would be difficult or impossible to capture with either bag seines or gill nets. We observed two limitations of eDNA metabarcoding. Read depth was not a good index of relative abundance, which limits our ability to infer relative biomass using single samples. Secondly, we observed detection bias in our eDNA results. Specifically, eDNA failed to detect two species of elasmobranchs present when water sampling was performed and eDNA also performed poorly compared to traditional sampling gears for some species of bony fishes. Despite these limitations, eDNA metabarcoding proved to be an efficient and cost‐effective alternative and compliment to traditional fisheries sampling gears for fishery‐independent monitoring of community structure and composition in estuaries of the Gulf of Mexico.