Dead fish found on Lake Koocanusa

In late August, there were reports of dead fish on Lake Koocanusa.

In late August, there were reports of dead fish on Lake Koocanusa, a scene similar to one that occurred on the lake two years ago.

It’s not entirely understood what is causing the death of thousands of kokanee salmon, but one fisheries biologist has a theory.

Mike Hensler, who works out of the Libby Field Station, said typically, this type of occurrence isn’t uncommon in large lakes, especially when it comes to kokanee salmon.

“They are relatively fragile fish – canary in a coalmine type of thing,” Hensler told The Free Press. “They are susceptible to dramatic changes more so than other fish are, and when we see these kinds of occurrences, it’s usually associated with hot, calm weather followed by a fairly dramatic storm event.”

The event in this recent occurrence was a heavy rainstorm that hit the area on Aug. 21.

Hensler said what he’s seeing is dead and dying fish on top of the surface of the lake with enlarged gas bladders.

Hensler said the kokanee are limnetic fish, which means they’re out in the middle of the lake most of the time, where other fish are not so they won’t be in the zone where the die-offs are occurring.

“When we were able to sample them as they were dying to see what was happening internally, what we’re finding was they had troubles with their GI track – with the digestive system – so they were sick,” he said. “Now, how they got sick, we don’t know because we never really found full stomachs, but they ingested something that’s a gas.”

There is possibly an algae of sorts is at the surface of the water the kokanee are getting into, but Hensler said that’s just a guess.

This time of year, especially in the evening, there are lots of fish at the surface and because it’s had the summer to heat up, surface temperatures can be lethal, Hensler said, adding the last time they checked the lake’s surface temperature, it was between 71 and 72 degrees Fahrenheit.

While that temperature could be lethal, Hensler said fish have the ability to dive back down into cooler water, but when a fish gets sick, it loses its ability to keep its place in the water column and if this happens, as they go back up towards the surface, their gas bladders expand and a sick or disoriented fish can no longer dive or swim down to decrease the pressure.

“It looks like the actual death has to do with warm water at the surface, but the reason they’re at the surface is still one of those – its’ a guess – and our guess is that there’s something there; something that they’ve ingested that’s causing them to get disoriented and sick.”

As far as he knows, Hensler said the water is safe to swim in, and should someone eat a kokanee, he suggests cooking it well but said there’s no indication suggesting that whatever is causing the die-off is harmful to humans.

While there were several thousand kokanee that died earlier this summer, Hensler said considering there are millions in Koocanusa Lake, it’s nothing to be alarmed about.

“Even if 10-20 thousands of them perish, it’s not the end of the world for kokanee in Koocanusa. It’s hard to say if this is a natural phenomenon, but it looks like it is,” he said, adding it tends to be something that happens in big lakes.

 

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Deer fawning season begins in B.C.

WildSafeBC is reminding people how to react if they come across a deer fawn

The Fernie Academy hockey players sign to play in the NA3HL

Dylan Baker, Chris Consolozio, and Bowen Arola continue their hockey careers in the NA3HL

Rivers, creeks flooding across the East Kootenay due to rainstorm

Residents evacuated in Fairmont, other properties on alert due to debris flow concerns

Southeast Kootenay school district set to reopen next week

Individual schools have creative timetables and schedules in order to adhere to public health orders

Fernie SAR responds to two calls this weekend

The calls reported an injured mountain biker and an abandoned kayak

B.C. records four new COVID-19 cases, Abbotsford hospital outbreak cleared

Four senior home outbreaks also declared over, eight still active

RCMP, coroner investigate murder-suicide on Salt Spring Island

Two dead, police say there is no risk to the public

About 30% of B.C. students return to schools as in-class teaching restarts amid pandemic

Education minister noted that in-class instruction remains optional

Trudeau avoids questions about anti-racism protesters dispersed for Trump photo-op

Prime minister says racism is an issue Canadians must tackle at home, too

B.C.’s Law Enforcement Torch Run for Special Olympics goes virtual

The annual event partnering RCMP with Special Olympians is dramatically altered by COVID-19

Introducing the West Coast Traveller: A voyage of the mind

Top armchair travel content for Alaska, Yukon, BC, Alberta, Washington, Oregon and California!

Bateman program encourages people to sketch outside, connect with nature

#MyNatureSketch initiative encourages Canadians to become ‘bright-eyed three year olds’

Be cautious expanding COVID-19 bubble, Dr. Bonnie Henry tells B.C.

Senior homes stay off-limits as schools, businesses reopen

Most Read