Backpack electrofishing can be used to collect adult lamprey

Objective: We 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-m(2) reach of Eel Creek, a small dunal stream in Oregon, United States.Methods: The 150-m(2) 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 mu S cm(-1), water temperatures ranged from 8.9 degrees C to 17.2 degrees 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.Result: We 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 mu W cm(-1), and the estimated mean body volume of the lamprey was 378 +/- 68 cm(3).Conclusion: The results suggest that backpack electrofishing is a useful method for collecting adult lamprey in streams with favorable habitat that concentrates them.