High temperatures, low snowmelt, could spell disaster for fish stocks
Salmon fishing in waters off the Comox Valley is outstanding this year, but hot temperatures and dry conditions could mean lower stocks in future years.
“We’re having excellent fishing in our local waters this year,” said Comox Valley Record outdoors columnist Ralph Shaw, who is an avid fisherman. But, “I’m also very concerned with the warm weather … the warm water — salmon can’t handle it.
“It just puts the temperature in the water beyond the limits that the fish can reproduce.”
Fisheries and Oceans Canada’s Puntledge River watershed enhancement manager Darcy Miller said if fish aren’t able to spawn or if juveniles die en route to the ocean, salmon stocks in the ocean could decrease in two to five years — as time to mature varies between salmon species.
“It’s not unusual for the Comox Valley to experience warm summers,” said Miller. “But, this summer, because we’ve had such a dry winter, low snow pack, generally most of the systems in our area are going to be negatively impacted by that with long-term effects, (such as) mortality in juvenile fish, and therefore, reduced adult abundance (in future years).”
As of Friday, the temperature in the Puntledge River was 18 degrees Celsius, which is stressful on the fish.
Though warm temperatures are a concern to Miller, he noted temperatures in the Puntledge can get higher.
“It is not uncommon that we reach temperatures of 20 degrees in the Puntledge River in the summer,” he said. “One year we hit 25 degrees — there was a lot of mortality of juvenile fish associated with that,” he said, adding nothing can be done to lower river temperatures.
Water levels are another matter. BC Hydro manages flows in Puntledge River and works with Fisheries and Oceans Canada to ensure water levels are high enough for fish.
Low water flows later in the summer and early-fall are a major concern in terms of spawning fish, said Miller, who notes BC Hydro is conserving water in the Comox Lake reservoir in preparation for spawning time.
“This is shaping up as one of our drier years,” he said, adding the weather forecasts could change from the warm, dry weather of late.”
But, “unless we get precipitation throughout the summer and in early-fall, it’s potentially going to be very tough … We deal with it each year, but this year has started a little bit under the bus.”
According to a July 10 BC Hydro status report, the Comox Lake reservoir is sitting at 134.3 metres, which is 0.7 metres below average for this time of year.
The snow pack was depleted about one month earlier than normal, and inflows to Comox Lake are at historical lows.
Low water levels also mean the chances of a retention fishery this September/October are less likely, and Miller said there is a “strong chance” there will be no retention this year. As well, Miller pointed out other Comox Valley rivers and streams don’t have the flow-control the Puntledge does, nor a hatchery program to assist fish, so fish in those waterways could be more severely impacted by low water conditions than fish in the Puntledge River.
One stress for fish is directly caused by the public, so can be avoided.
"People swimming near fish, around fish, chasing fish in the little pools, that stresses the fish," he said, urging the public to refrain from interfering with fish when using the river for recreation this summer.
On a positive note, Miller points out fish survival depends greatly on the marine environment and marine waters around the Valley are producing healthy fish.
"The fresh water aspect is just one part of what the adult abundance will be a few years down the road," he says.