Wednesday was another hot summer day in the Comox Valley with temperatures pushing 30 degrees and while people tried to escape the heat with a dip in the Tsolum River, they didn’t get much relief.
Water temperatures in the river are about 28 degrees, and salmon are having a particularly hard time in the warm water.
“Salmon aren’t happy after about 17 degrees,” said Wayne White, president of the Tsolum River Restoration Society. “Fifteen degrees is ideal, 17 they’re starting to get stressed and when we’re in the high 20’s they don’t have a chance.”
Researchers are seeing a die-off of up to 50 per cent of juvenile Coho in the river and are worried about incoming salmon if the waters don’t rise and cool down soon.
“Essentially it’s toxic to the fish,” added White. “The only fish that survive are the ones who do find the cool pockets, the deeper pools, some groundwater coming in, some deeper shade in the riparian areas.”
The warm water also makes the fish more lethargic and easier to prey on.
“We walk the river every evening and see dead fish pretty much every evening,” said Caroline Heim, Tsolum River Restoration Society program coordinator. “They’re just more vulnerable especially in the shallow waters. Kingfishers can dive down and take them, mink can go in the water, they are more vulnerable when they’re all grouped together like that.”
The Koksilah River in the Cowichan Valley is seeing a similar situation this summer and is at Drought Level 3.
The B.C. government has put the Tsolum at Drought Level 4 meaning “adverse impacts are likely” and “regulatory action is being considered to avoid significant or irreversible harm to aquatic ecosystem.”
Water conservation by area licence holders is currently only being urged.
It says fish habitat is “reduced due to dewatering of riffles and disconnected side channels” and that water temperatures are “lethal.”
The headwaters of the Tsolum are on Mount Washington and the restoration society is considering a deep water intake in Wolf Lake near the base of the mountain to help feed the river at times like this.
Another issue is forestry.
“We have a vibrant forest growing up there but that second growth forest does utilize a lot of water so there are concerns whether that’s affecting the groundwater availability and the surface water availability in the river itself over time,” said White.
White says riparian areas that provide shade and cooler water are disappearing and the group is actively working to restore them along the river.