Parasites on Pink Salmon (Oncorhynchus gorbuscha)

Observation: Most all of 12 pinks had varying levels of this parasite load. Newer to AK so unsure if this is common parasite? Normal? How widely spread? 90% of the fish had these parasites. Number of parasites per fish ranged from 1-12, most below lateral line from tail to anal fin. These were caught just north of Ketchikan. It is another stressor on salmon but would like to know if this parasite load is significant.

LEO says: These look like sea lice. In an ADF&G publication on salmon and sea lice, Amy Carroll writes: "There are two species of sea lice found on salmon, Caligus elongates and Lepeophtheirus salmonis. C. elongates affects many species of marine fish, while L. salmonis is found only on salmon and related species. Sea lice are common on adult salmon, and fall off as the salmon return to freshwater streams to spawn. This insures there are no surviving sea lice where the juvenile salmon out-migrate in the spring. Although an adult salmon may be relatively unaffected by an infestation of sea lice, the juvenile salmon’s small size and thin skin renders them highly vulnerable to a sea lice infestation – lethally vulnerable. Pink and chum juvenile salmon, furthermore, lack scales, making them even more vulnerable to the effects of sea lice than their scaled relatives Chinook and sockeye. The open lesions compromise a small fish’s ability to maintain its saltwater balance."

Source: Alaska Fish and Wildlife News "What Are Sea Lice?"

ADF&G Consult: Jayde Ferguson, Fish Pathologist, writes: "Yes, this does look like sea lice. Here is a link to our chapter on this parasite in our booklet. The impact on the fish is generally low unless there is an extremely high parasite load, much more than 12. Also only a few fish in a population tend to have such high loads."