Volunteer Angling and Technology‐Based Solutions Provide the First Estimate of Sea Lice Infections for Wild Coastal Cutthroat Trout Oncorhynchus clarkii clarkii

Abstract

Anadromous Coastal Cutthroat Trout Oncorhynchus clarkii clarkii are one of the least studied salmonids but are a highly prized target in sport fisheries in coastal waters of the Pacific Northwest. Despite an observed high prevalence of ectoparasite infections, described by sport anglers as “sea lice,” there is a paucity of data available on the spatial and temporal occurrence of infections on Coastal Cutthroat Trout. We collaborated with the angling community through social media engagement and an online application to report ectoparasites observed on sport catch. In 2018, we received voluntary reports for 1,493 Cutthroat Trout and 416 salmon catch events in marine waters from the province of British Columbia and the states of Washington, Oregon, and California. These data demonstrated that the number of argulids and copepods per trout varied according to body size, capture month, and area. To evaluate accuracy of voluntary parasite counts, we compared results to parasite counts on cutthroat from sampling events conducted by trained biologists. For both voluntary angler reports and those of biologists, spring months had a lower prevalence of argulids and copepods, argulids were common on trout, but absent on salmon, and larger trout were associated with an increased number of argulid and copepod infections.