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Biological Hazard – Unexplained Mass Die-off (Fish): Okanagan Lake, British Columbia


Biological/Eco-System Hazard – Mass Die-off (Fishes)
North America – Canada | Pacific West Coast, British Columbia

Published Date: 2016-07-22 12:39:21
Subject: PRO/AH/EDR> Undiagnosed die-off, fish – Canada: (BC) RFI
Archive Number: 20160722.4362760

Date: Monday 18 Jul 2016
Source: Global News [edited]

Thermal shock or disease could be factors into a recent kokanee [non-migrating form of sockeye salmon] die-off in Okanagan Lake [British Columbia] that has some residents concerned.

“We headed out on the lake and noticed the kill off of these fish [and] we were quite alarmed. It’s the 1st time we’ve seen in it in our 10 years of boating,” a West Kelowna resident Scott Thresher said.

“There are about 6-inch [15.2 cm] kokanee and they’re right across the lake, both sides and in masses and we’ve never seen it before.”

[The man] said he was boating on the lake near the West Kelowna Yacht Club when he saw hundreds of dead fish. “Of course you immediately think that the lake has been poisoned or something but then we realized that it was just this particular species of fish and nothing else was floating at the top,” he said.

The province said sudden changes in water temperature or a viral outbreak could be why more than 1000 kokanee have washed up on the shores of the lake since [Thu 14 Jul 2016].

“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 deeper into the lake,” public affairs officer for the Ministry of Forests, Lands and Natural Resource Operations, Greig Bethel said in a news release.

Bethel said tissue samples are being analyzed by staff at a fish health lab in Duncan to find out if disease was a factor in the recent kokanee deaths.

“Die-offs in other lakes have been linked to the infectious hematopoietic necrosis virus — IHNV,” he said.

While the numbers of dead fish that are washing up on valley shores is alarming to some, Bethel said the die-off won’t have a large impact on the lake’s overall kokanee population.

“Last year [2015], biologists counted more than 336 500 spawning kokanee on the lake, the most since annual counts began in 1992,” he said.

[Byline: Neetu Garcha]

Communicated by:
ProMED-mail from HealthMap Alerts

[For a picture of kokanee (_Oncorhynchus nerka_) go to

Infectious hematopoietic necrosis (IHN) is a serious disease of several species of juvenile Pacific salmon reared in fresh water, particularly sockeye salmon. The latter is the same species as kokanee. In fact, kokanee are freshwater sockeye salmon. In British Columbia, IHN virus has caused severe losses among sockeye and kokanee salmon. – Mod.PMB

Maps of Canada can be seen at and The location of Okanagan Lake can be seen at – Sr.Tech.Ed.MJ]

See Also

Viral hemorrhagic septicemia, fish – Canada: (NF) OIE 20160627.4312377

Undiagnosed die-off, fish – Canada: (QC) RFI 20140919.2787149

Die-off, fish – Canada: (ON) lake inversion susp 20120909.1287307
Die-off, fish – USA (06): (OH) RFI 20120827.1266581
Die-off, fish – USA (02): (GA) comment 20120601.1153265
Die-off, fish – USA: (GA) pollution susp. 20120531.1152141

Undiagnosed die-off, fish – USA (02): (GA) columnaris 20110528.1641

Undiagnosed fish die-off – USA (04): (WV, OH, PA) columnar 20100610.1946

A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases

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