Using a Customized Portable Deepwater Electrofisher to Assess Larval Lamprey Populations in Irrigation Canals

Water diversions are very common in agricultural landscapes, providing water to irrigate a diverse range of crops. Larval Pacific Lamprey Entosphenus tridentatus are vulnerable to entrainment during the irrigation withdrawals and can be exposed to desiccation or predation during dewatering at the end of the irrigation season. A customized portable deepwater electrofishing system was deployed to determine larval lamprey densities at two large scaled irrigation diversion canals located on the Yakima River in eastern Washington. The system components can be easily transported to a remote survey site due the number of components and minimal total weight. The surveys were conducted in the fall during the dewatering period in 2015 and 2017, and the densities for larval lampreys ranged from 0.8 to 8.8 fish/m(2) at the Sunnyside Canal and 4.2 fish/m(2) at the Wapato Canal (2015 only). Our results indicate that the use of the deepwater electroshocking system was effective at determining larval lamprey presence and densities in hard-to-sample irrigation canals.

Automated summary

This study investigated the impact of water diversions in agricultural landscapes on larval Pacific Lamprey, using a portable deepwater electrofishing system to determine larval lamprey densities in irrigation canals. Results indicated the effectiveness of the system in determining the presence and densities of larval lampreys in hard-to-sample irrigation canals.