High fish mortality may occur after record-breaking BC floods

Some fish species may suffer high mortality as a result of catastrophic floods in southern BC last week, warned some experts and observers.

Pink salmon are at particular risk, says biologist Marvin Roseneau, as they lay eggs in the main stem of the species Fraser and the Vedder/Chilliwack River.

Most of their eggs are laid in the fall and hidden in the gravel to incubate until hatching in the spring.

“The flood almost certainly wiped away the gravel,” he explains.

“Once the embryos are washed off the gravel, the predators eat them, they burn to death – it’s over for them.”

Roseneau, who teaches ecology and fish management at BCITChinook said coho salmon and steelhead salmon may also be affected to a lesser extent.

“We will quantify it a year and a half from now when the adults come back. We’ll see if those runs completely fall apart as a function of the event. “

He estimated salmon mortality at as low as millions for juveniles and billions for embryos, and clarified that not all fish and eggs can survive, due to other natural causes.

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Ron Houniet, co-director of the Fraser Valley Fishing Guides Association, added chum trout to the list of species whose eggs may have been “washed away” by fast-flowing flood waters.

“It would be absolutely devastating for the future of those salmon schools,” he said in an interview.

“We have other issues here like fish loss to commercial fishing, climate change, and with this happening here it will just be another impact.”

He also estimated that billions of eggs were washed away by the water and “didn’t stand a chance”.

In addition to the effect of flushing the gravel away, Simon Fraser University professor of earth sciences Brent Ward said floods can deposit dangerous amounts of gravel that can affect acne.

“The fish needs a certain grain size for the redfish to lay their eggs in the right places, and if there is so much mud that the water becomes very cloudy, then you know it can really have a serious effect on your health,” he explains. fish and kill them,” he explained.

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BC Agriculture Minister Lana Popham said land-based fish farms were also affected by the disaster, but the damage had not been estimated.

“The losses are yet to be accounted for, but we believe all the fish are presumed lost,” she told a news conference on Thursday.

“This is tilapia and sea bass. Unfortunately, we also have a commercial Chinook hatchery on Vancouver Island that has also been damaged by flooding. ”

The November 14 and 15 floods had devastating effects across southern BC, kill five people, displaced thousands of people and destroyed critical infrastructure. More than 20,000 farm animals have also been lost.