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.


Just Posted

Fernie local apprehended after break and enter

Elk Valley RCMP Early in the morning of Saturday, March 17, an… Continue reading

Former Riders coach reflects

Mohr looking for new opportunities after contract ends

Athletes ready for world stage

Three Fernie athletes to compete in the world’s biggest junior freeride competition.

Hydro prices to surge

Elk Valley businesses brace for 3 per cent Hydro rate increase.

Elk Valley rallies for car fire victim

Aussie loses everything in car fire

Ottawa proposes restricted pot labels, packages

Packaging will include red stop sign with marijuana leaf and ‘THC’

Pro-Trump protest sign with F-word is OK, court rules

Judges say Ontario man can protest publicly, even using vulgar language

Sparwood skaters impress

Club farewells coach

Army cadets test survival skills

Cadets endure -18C conditions

Exhibition builds compassion

Opioid use in focus

Medicinal cannabis patient shares story

Fernie mom spreads compassion

Epic deal for FAR

RCR signs new partnership

VIDEO: Police officer looking for distracted drivers gets hit by truck

Road safety investigator clipped by trailer while patrolling busy intersection

YVR wants you to help name three new puppies

Say hello to the Vancouver Airport’s new assistance pups

Most Read