Survival of Larval Lamprey to Electrofishing, Suction Dredging, Anesthesia, and Handling in the Pacific Northwest

Native lamprey populations are declining worldwide. In the Pacific Northwest there has been increased attention given to research and management of these ecologically and culturally important species.  As research efforts increase, concern has been given to the effects of sampling and handling, with little to no attention on the larval lifestage.  We examined the survival of larval Pacific and Western brook lamprey from backpack electrofishing, deepwater electrofishing and suction dredging, and anesthesia and handling.  Evaluations were performed in both laboratory and field settings. In all cases, survival was evaluated for 96 hours post treatment. Preliminary results indicate that survival was high; average mortality for larvae <70 mm total length (TL) was less than 2%, for larvae >80 mm TL and controls average mortality was 0%.  The typical electrofisher settings for larval lamprey (i.e., low-pulse, low-frequency) are likely relatively benign in the short term.  Long-term effects such as delayed mortality, behavioral changes, and growth effects that could lead to secondary mortality are not well understood.