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How many samples are enough? Trying to determine guidelines for fish eDNA sampling to capture full fish assemblages in lakes
Citation:
Pilgrim, E., C. Hatzenbuhler, G. Peterson, A. Szczepanski, C. Larson, A. Trebitz, AND J. Hoffman. How many samples are enough? Trying to determine guidelines for fish eDNA sampling to capture full fish assemblages in lakes. 6th Annual eDNA Technical Exchange Workshop, Virtual, OH, January 24 - 26, 2023.
Impact/Purpose:
Present ongoing fish eDNA research to an audience experienced with eDNA work to show our results and gather their input.
Description:
As many of us have learned, the distribution of eDNA for any given species within an ecosystem is not even or uniform. For capturing all the fish species present within lake, one or a few samples is unlikely to delineate the full assemblage. This work seeks to create guidelines on how to sample eDNA within a lake with the best chance of capturing as many fish species as possible. Using lakes in Minnesota in three size categories, we developed an ‘over-sampling’ for collecting fish eDNA. Sampling locations were scaled to the size of each lake and chosen along multiple depth contours (fringe <5 feet, nearshore 5-15 feet, open water >15 feet). We collected water quality/habitat data and three 250 mL surface water samples at all sites and additional near bottom samples at a random subset of open-water sites. In total, 1000+ samples were collected from nearly 300 sites over 8 lakes. Water samples were filtered and three pooled PCR replicates from each were metabarcoded for 12S (Am12S) and 16S (Ac16S). Fish species detections by eDNA were compared to historical fish assemblage data for each lake. We expect results to provide insight on how States could efficiently incorporate eDNA sampling into lake surveys with maximum results from the minimum effort to increase the probability of detecting new invaders and native fish species that may be missed by conventional methods.
