Nonlethal assessment of juvenile pink and chum salmon for parasitic sea lice infections and fish health

Industrial salmon farming has been correlated with infestations of parasitic sea lice Lepeophtheirus salmonis in adjacent wild juvenile salmonids and declines of sympatric wild salmonid populations. Prohibitively large financial, human, and logistical resource requirements prevent the implementation of long-term, large-scale monitoring programs to assess the effect of farms on wild salmonids. We report a novel nonlethal sampling procedure for quantifying louse abundances and measures of fish health on wild juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta during their early marine life history phase. The method significantly reduces the resource requirements of sampling programs and provides a desirable nonlethal alternative for studying depressed or threatened populations. The simplicity of the protocol facilitates public participation, further decreasing costs while increasing the potential spatiotemporal coverage and resolution of future research-monitoring programs.