Record warm ocean temperatures pose threat to B.C. salmon

Record warm ocean temperatures combined with low, unusually warm rivers pose a double threat to B.C. salmon, prompting officials to curtail some fisheries.

Salmon face double threat from weather changes

Record warm ocean and river temperatures could threaten B.C. salmon numbers, federal fisheries officials say. (CBC)

Record warm ocean temperatures combined with low, unusually warm rivers pose a double threat to B.C. salmon, prompting officials to curtail some fisheries.

​The reduced fisheries are part of a cautious approach to ensure that a healthy number of salmon return to river spawning grounds.

Ocean scientist Ian Perry said two unusual weather factors have dealt simultaneous blows to B.C. salmon numbers; Higher than normal ocean temperatures and warmer and lower river levels.

Perry said warmer ocean conditions — up to three degrees higher than normal -- arrived in the northeast Pacific Ocean in early 2014.

Federal scientists say water temperatures in the northeast Pacific are approximately 3 C above normal. (Fisheries and Oceans Canada)

The warm water killed off some of the nutritious food that salmon normally eat and helped breed more predators.  As a result, the younger salmon that swam to sea after the warm spell struck might not survive or return thinner and weaker.

"We are expecting there to be fewer numbers coming back in the next one to three years," Perry said in a telephone conference news update.

Survival threatened

"They've come into an environment with poorer fish food and a lot more predators," Perry said. "We anticipate this will affect their survival, certainly their growth and their survival."

Perry said the ocean temperatures are the warmest "we've ever observed since 1948 in the east sub Arctic Pacific,"

Headed the other way, salmon are returning to rivers that are warmer and lower due to the prolonged hot, dry weather.

Scientists say salmon numbers are higher in the Nass and Skeena rivers than further south in the Fraser River .As a result, officials have delayed salmon fishing in the lower Fraser for two weeks. Recreational fishing is closed on the southern end of Vancouver Island.

Previous research has shown that the swimming performance of migrating salmon starts to decline when water temperature hits 18 degrees Celsius. During some hot summers, between 40 per cent and 90  per cent of Fraser River salmon have died before they can spawn.

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