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Detection and identification of lampreys in streams using environmental DNA
1 University of Manitoba, Winnipeg, MB
2Sea Lamprey Control Centre, Sault Ste. Marie, ON
3Michigan State University, East Lansing, MI
Control of sea lampreys in the Great Lakes requires accurate assessment of the distribution of this species in natal tributaries and the ability to distinguish sea lampreys from the four lamprey species that are native to the Great Lakes; two of these native species are of conservation concern. Environmental DNA (eDNA) has been used to assess the diversity and abundance of aquatic species by detecting the DNA of an organism in the water instead of locating the organism itself. We developed PCR-based assays to distinguish among the four ‘species’ of Great Lakes lampreys (sea, American brook, chestnut, and silver/northern brook lampreys), and employed these in the development of efficient and cost-effective environmental DNA (eDNA) methods. This included developing rigorous quality control protocols (e.g., to guard against false positives), performing initial laboratory testing of the assays to refine and calibrate the methodology, and demonstrating in the field—for the first time—that both spawning and larval sea lamprey populations can be detected in streams using eDNA techniques.
In 10L aquaria in the lab, we found that higher larval densities had a positive effect on eDNA amplification success, while both lower temperatures and higher flow rates had a negative effect on amplification success. In the field, we were able to detect an increase in eDNA in the Little Thessalon River during the spawning run in May; this elevated eDNA signal persisted for approx.1 month after all adults had died but had attenuated by late July. Our eDNA assay was also able to detect larval lampreys in natural stream systems, but only in one of three high density streams and in one medium density stream.
Given the success of detecting both spawning and larval populations of sea lamprey, the developed sea lamprey eDNA detection methods could potentially reduce cost and increase efficiency of current management strategies by serving as a “red-flag” system, identifying streams with spawning adults as well as streams with large larval populations that require more thorough assessment. However, to minimize the occurrence of false negatives, further refinements will be necessary to improve assay sensitivity.