Movement Patterns of Outmigrating Juvenile Sea Lamprey

Sea lamprey (Petromyzon marinus) research and control efforts regularly target larval and adult stages, but little focus has been placed on the metamorphosing juvenile (transformer) stage because of logistical challenges working through the winter. This study was designed to determine the spatial and temporal patterns of out-migrating transformers. Sampling occurred during fall and spring 2012-13 and 2013-14 in Malletts Creek, VT, and Morpion Stream, QC. Vertical stacks of drift nets were placed across the stream channel to sample the bottom and middle of the water column; floating drift nets were used to sample the surface. During the four sampling seasons, 655 transformers were captured. Most lampreys were captured in the middle of the stream channel rather than along the edges, and more were captured in the middle of the water column as opposed to near the bottom. Increased capture rates were correlated with increased discharge events and water temperatures below 5°C. High debris loads, cold temperatures, and ice made standard sampling methods difficult and often ineffective during these periods.  Novel techniques should continue to be developed that can target this vulnerable life stage and lead to another effective control method of this parasitic species.