Backpack electrofishing can be used to collect adult lamprey

Abstract

AbstractObjectiveWe describe a new method for collecting adult Pacific Lamprey Entosphenus tridentatus in wadeable streams using a backpack electrofisher with pulsed direct current at 300 V, 50 Hz, and a 4‐ms pulse width in a 150‐m2 reach of Eel Creek, a small dunal stream in Oregon, United States.MethodsThe 150‐m2 collection reach was predominately coarse substrate (20% boulders, 60% cobble, 15% pebbles, and 5% sand), whereas the substrate in the remainder of the 4.2‐km‐long Eel Creek is predominately sand and silt. The specific conductivity of the stream was 83.7 μS cm−1, water temperatures ranged from 8.9°C to 17.2°C, and water depth was less than 1.2 m. One person electrofished while gradually moving downstream, and up to six netters that were stationed up to 6 m away covered most of the channel width and caught the lamprey as they emerged from the substrate and floated or swam downstream.ResultWe collected 118 adult Pacific Lamprey (mean catch per unit effort = 29.5 lamprey h−1; range = 4–80 lamprey h−1) measuring 504 ± 54 mm TL (mean ± SD) over eight collection events during 2018–2021. Of these 118 fish, 117 were subsequently anesthetized, handled, tagged, and released within a few hours with no mortalities, external injuries, or abnormal behavior. One tagged lamprey (0.8% of all collected lamprey) died during a second collection 35 d later. The estimated peak power output was 267.7 μW cm−1, and the estimated mean body volume of the lamprey was 378 ± 68 cm3.ConclusionThe results suggest that backpack electrofishing is a useful method for collecting adult lamprey in streams with favorable habitat that concentrates them.