Record hot Pacific Ocean temperatures that have degraded the marine food supply since the fall of 2013 are likely to hurt B.C. salmon returns not just this summer but for the next one to three years.
That’s the prediction of Ian Perry, an ocean scientist with Fisheries and Oceans Canada.
He said the effects may be relatively minor this summer – with returning sockeye salmon that are only slightly thinner or smaller than usual – but worse over the next few years.
That’s because the sockeye now returning experienced relatively normal temperatures when they first headed out to sea as juveniles in early 2013.
Unusual weather patterns that year meant there wasn’t the normal deep mixing of ocean layers in the northeast Pacific and the surface temperatures got steadily warmer.
The water in the Gulf of Alaska was three degrees above normal by January 2014 and there were record hot temperatures last summer.
The runs that will return from 2016 to 2018 will likely have faced longer exposure to hot ocean temperatures, which result in poor, less nutritious plankton for salmon to feed on, and can also bring more predator fish north to devour salmon.
“The juvenile salmon coming out of the river this spring in 2015 are coming into an environment that is very different from what they’ve normally evolved to,” Perry said.
“We anticipate this is going to affect their growth and their survival. And we expect there will be fewer numbers of them coming back in the next one to three years.”
The sockeye that survive the ocean to make their spawning run this year will face the danger of hot river temperatures and low flows.
Federal habitat research biologist David Patterson said record high water temperatures are being measured throughout the Fraser River system.
He said the water is 4.5 degrees hotter than normal at Hope – an “exceptional deviation from the norm.”
Hot rivers make it harder for salmon to migrate upstream, reproduce and recover from fishery capture, and make them more susceptible to disease.
Patterson said the biggest problem is often that low flows and hot water force salmon to hole up in unsuitable areas, and if they wait too long, water levels may drop further in their eventual spawning grounds, reducing the available habitat.
Although nearly seven million Fraser River sockeye are projected, large numbers could die before they spawn.
El Nino conditions are expected to last at least through fall, meaning continued dry, hot weather is likely in B.C., with no short-term relief for salmon.
Chinook angling ban extended
DFO has extended a ban on sport fishing for chinook salmon for an extra two weeks due to low levels of early Stuart sockeye and adverse conditions, said Jeff Grout, regional salmon resource manager. That ban is in effect everywhere downstream of Mission until July 31.
“We’re taking a cautious management approach to how we manage our fisheries,” Grout said.
He said that may mean fishing restrictions or bans later in the season even as more abundant pink salmon arrive in order to avoid a bycatch of weaker stocks, such as Interior coho.
DFO officials say they’re stepping up enforcement patrols to deter and catch poachers. Anyone who spots illegal fishing can call DFO’s Observe Record Report line at 1-800-465-4336.