Reports of dead salmon on N.L. rivers likely caused by high water temperatures, experts say

Chris Humber says he's seen a lot as an avid angler over the years but he doesn't remember the waters at Great Rattling Brook near the Exploits River ever being this warm.

"We usually gets warm temperatures every summer, right? But it seems like this year, it's been like remarkably hot weather. And it's brought the temperatures in the river up like drastically, quick," Humber told CBC News on Tuesday.

High temperatures of over 20 C are being reported at rivers across Newfoundland and Labrador, according to Craig Purchase, a professor of fish biology at Memorial University.

Other anglers who have shared photos with CBC News have reported dead salmon washing up at Lower Falls in Dunville, near Placentia.

While Humber said he hasn't seen any dead salmon himself, he and others fishing at Great Rattling Brook have decided to leave the fish alone for the time being.

"We don't know the scientific proof on it, but we feel that you're not doing the fish any good by hooking and releasing," he said. "We feel it's better to leave the fish alone, let them do their thing and get up to their spawning grounds."

A total of 77 salmon fishing rivers are facing modified closures — which opens fishing areas only in the early morning hours, when temperatures are lower, but closes them after 10 a.m. — by the Department of Fisheries and Oceans, which cited extremely high water temperatures and a lack of rainfall in a press release Tuesday.

"DFO will continue to monitor river conditions and reopen closed rivers when environmental conditions improve," the release said.

Purchase said water temperatures surpassing 22 and 23 C have been seen before — especially in the past few years — but seeing those reported temperatures for an extended period is concerning.

"I haven't observed [dead salmon], but this is entirely predictable. You would expect salmon to die under these conditions," Purchase said.

"They're not adapted to deal with this. They can deal with temperatures in the mid-20s maybe, if they're not exerting too much energy for a few days.… But high 20s, these things are not adapted to do that. And they're not going to do well at all."

Purchase said cold-water-adapted fish like salmon and trout don't do well in climates with high water temperatures. Higher temperatures affect fish metabolism and puts them under stress, he said, usually sending them into deeper pools of lakes and rivers in search of colder water.

Calvin Francis, a member of the Newfoundland and Labrador Advisory Committee for the Foundation for Conservation of Atlantic Salmon, said he's already seen it happening.

"For the last few weeks I don't know of anyone who has landed a salmon. But that's nothing unusual, because these salmon are smart. They're survivors, they go to these pools," he said. "As long as they stay in these positions, we're not going to catch any — which would be a good thing, no threat to the salmon."

Purchase said he's concerned about warm water temperatures persisting, especially as the province and the rest of the world deal with climate change.

"If we continue to get to see temperatures like this on a regular basis, yeah, it would be a problem for many of our salmon populations," he said.

"In other places that have similar latitudes then us, they cannot support salmon because it's too warm. So in the future, we may easily lose some proportions of our salmon population entirely because of something like this, or certainly the productivity of other populations could be affected as well."

Full river closures needed, says NunatuKavut

Purchase says the modified closure of rivers is the best strategy to take, because anglers mostly fish in the early mornings anyway and wouldn't intentionally hurt stocks by hooking and releasing at dangerous times, but the NunatuKavut community council wants to see the closures go a step further.

"Looking at the temperatures that we're faced with here his summer in southern Labrador, [we think] that the best thing to do right now we would be to obviously put a full temporary closure on hook-and-release on a lot of the major salmon rivers," George Russell Jr, the council's director of environment and natural resources, said Monday.

CBC News asked DFO for comment but didn't receive a response by publication.

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