No abstract

Salmonids of the genus Oncorhynchus, distributed throughout the Pacific Rim, can be infected by the gill lice species Salmincola californiensis (Dana, 1852), which makes them one of the most broadly distributed gill lice species. Despite their broad distribution and valuable obligate salmonid hosts, relatively little is known about S. californiensis. We evaluated effects of temperature on timing of S. californiensis hatching and survival of copepodids, and provide information on brood size and variability. Our results suggest that temperature was a primary driver of timing of S. californiensis hatching and post-hatching survival. Prior to this study, the free-swimming stage of S. californiensis was reported to survive approximately 2 days without a suitable host. We observed active copepodids 13 days after hatch with some individuals from most (>90%) viable egg sacs at all temperature treatments surviving ≥5 days. Our findings indicate that warmer temperatures could increase development rates of gill lice at certain life stages, potentially increasing fecundity. This information coupled with predictions that warmer water temperatures could intensify crowding of coldwater fishes, stress, and parasite transmission suggests that climate change could exacerbate negative effects of S. californiensis on ecologically and economically important salmonids.

Salmon and trout of the genus Oncorhynchus are widely distributed throughout the Pacific Rim region, historically supporting largescale fisheries in their native ranges. Managers have introduced Oncorhynchus salmon and trout widely in freshwater systems to create new recreational and sport fishing opportunities. For example, kokanee salmon (lacustrine sockeye salmon, O. nerka, Walbaum) have become an important sport and food fish in many North American lakes (Biser, 1998;Nelson, 1968;Wydoski & Bennett, 1981). They have been introduced in systems as large as the Great Lakes and many smaller waterbodies in western states such as California,