B.C. weather jeopardizes salmon run. Here's how

Monday, June 29, 2015, 9:30 PM - Rising temperatures and dropping water levels are putting the adult salmon population in British Columbia at risk.

The summer season has wasted no time heating up in western Canada. Record-breaking temperatures soared beyond the 40-degree mark in the past week. The heat, coupled with little to no rainfall, has provinces like British Columbia facing a potential drought.

Water levels are dipping alarmingly low in rivers across the province, ultimately effecting a variety of wildlife, including various species of salmon.

An expansive network of rivers and streams serve as highways for the annual salmon run, which depending on the species, can begin from spring through fall.

Each year, adult salmon instinctively begin a long journey back to waters where they were born.

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The sockeye salmon are among the first to begin their return from coastal ocean waters to freshwater streams and lakes, headed for their hatching grounds.

“The fish entering these lakes are the first to be affected by warm waters,” explains Dr. Brain Riddell, President and CEO of the Pacific Salmon Foundation. “In Barclay Sound, on the west coast of Vancouver Island, we’re seeing fish delaying in the salt water.”

Once a salmon enters fresh water, it cannot return to the sea. Fish will instead wait until fresh water temperatures cool before making the transition, thereby delaying their journey home.

“With the extremely warm, early summer, they’re moving very slowly into the river because it’s too warm,” Riddell says.

Warming waters can be detrimental to adult salmon, even causing death if temperatures begin to climb above 20 degrees Celsius.

While the heat is a major concern, a lack of rainfall along the south coast is also taking its toll. Low snowpack levels over the past winter have also diminished typical water levels in rivers and lakes.

“Vancouver Island is one of the first places you starting seeing concern about water flow,” says Riddell.

Low water levels warms up more quickly, and also effect the trajectory and velocity of water flow.

Salmons headed for spawning are also barreling towards a fatal end. Once the salmon reach their former hatching grounds, they lay and fertilize their eggs in the gravel of riverbeds to incubate over the winter months. But the exertion of swimming home and mating is often the last hurdle they will ever make.

Most species of salmon die after spawning. Their bodies will being to break down as they complete their run, making them more susceptible to the physical effects of the increasingly warmer water this year.

“At this point, the race is on as to whether the salmon can actually find a spawning site and mate before it dies,” says Riddell.

Rising water temperatures also limit the capacity to carry oxygen, further stressing the salmon as it completes the most strenuous act of its short life.

But not all hope for a successful Pacific salmon run is lost.

Extreme summer conditions can still be offset by a typical winter season. If conditions are mild and a sufficient number of eggs survive the winter months, the population will bounce back.

Flash floods and a mix of rain and snow events threaten to disrupt river flows, endangering salmon eggs buried in underwater gravel.

“Sockeye are the salmon we’re most concerned with now in terms of entering fresh water,” says Riddell. “But it won’t be very long until we start to see Chinook salmon migrate up the Fraser River and other coastal rivers.”

Steelhead trout may also be affected by summer extremes. These fish typically spawn in the spring, putting their eggs at the mercy of warming waters and low levels before they are ready to hatch.

Intense summer heat and drought has been a recurring pattern for B.C. summers, and warm waters is not something that salmon will be able to adapt to quickly.

Measures are being taken to address the growing concern and need for control over water flow through the use of dams and other infrastructure in the future.

For now, Fisheries and Oceans Canada continue to post orders against fishing in certain spots in order to protect spawning areas until the season is over.

A decline in the salmon population would set off a detrimental ripple effect to other species and wildlife. Many animals, most notably bears, feed on live salmon as they make their runs upriver to spawn. As the majority of salmon die after spawning, their decaying bodies serve as food for other river creatures like birds and otters.