Sampling Methods and Survey Designs for Larval Lampreys

Knowledge of the biology, distribution, and abundance of lampreys (Petromyzontiformes) is critical to inform conservation actions for native species and to inform control measures for the invasive Sea Lamprey Petromyzon marinus of the Laurentian Great Lakes. Lampreys have complex life cycles that include a freshwater larval stage in which they burrow into substrates consisting of fine sediment and organic matter. The larval stage is frequently targeted in research and monitoring; given this interest, a review of survey designs and methods is needed. Our review identified 12 different sampling methods for larval lampreys and focused on one common method-backpack electrofishing in wadeable habitats. Our review also identified eight research and monitoring questions that have been addressed for larval lampreys in field studies, including distribution, species identification, life stage occurrence, abundance, length frequency, habitat use, residence and movement phenology, and species status. Each question provides unique information and poses distinct challenges to data acquisition and interpretation. The objectives guide decisions about study design and scope of inference. The scope of inference is determined by the size, spatial distribution, selection method, and number of sampling units within and across habitats, which determine the spatial and temporal scales under which results can be interpreted. The sampling unit size can span orders of magnitude from microhabitats to river drainages, ultimately informing management decisions at several spatial scales. The intended scope of inference and the interaction between biological questions and the fiscal and logistical capabilities of the study are integral considerations when designing an effective larval lamprey survey.