More than 1,000 kokanee have washed up on the shores of the lake since last week, a sign of either thermal shock or disease, biologists say.
Recent wind storms or a viral outbreak are potential causes of the ongoing die-off of Okanagan Lake kokanee, a landlocked sockeye salmon species that is second only to rainbow trout as a game fish in B.C.
While biologists have yet to pinpoint what is causing the kokanee deaths, previous die-offs in Okanagan Lake and elsewhere have been associated with strong winds that can send warm surface water into deeper into the lake. Such sudden changes in water temperature can be deadly to kokanee.
Die-offs in other lakes have been linked to the infectious hematopoietic necrosis virus – IHNV. Staff at the Freshwater Fisheries Society of B.C.’s fish health lab in Duncan are analyzing kokanee tissue samples to find out if disease was a factor in the most recent deaths.
At this point, the die-off is not severe enough to have a significant impact on Okanagan Lake’s overall kokanee population. Last year, biologists counted more than 336,500 spawning kokanee on the lake, the most since annual counts began in 1992.