The effects of a summer of environmental catastrophes were felt everywhere in Canada, from its vast boreal forests to a river on Vancouver Island once fished by Hollywood royalty.
It remains a mystery. Government officials found partially treated wastewater in the river a couple of weeks after the fish were found, but they have yet to draw conclusions about its impact. Local scientists suspect the bigger culprit is climate change, which has contributed to the decline of salmon populations in British Columbia by increasing droughts and heat waves.
A biologist, swimming in a wet suit for miles downriver from where the juvenile fish, or fry, had been found, discovered hundreds more dead inside pools at the bottom of the river. Further downstream, past eerily “barren zones” with no fish at all, he found dozens of dead adults inside larger, deeper pools — foot-long rainbow trout and even bigger brown ones.
“We’ve never had a significant fish kill like this in the Cowichan River, or at least in living memory,’’ Mr. Rutherford said. “The event is still under investigation. But if there was more water in the river, if it wasn’t this hot, the impacts would have been less. Salmon are cold-water species. Things may not have in the past tipped them over the edge. Now they do.’’
Government investigators found partially treated wastewater from a local treatment facility in the river 14 days after the dead fry were first discovered, but have not reached any conclusions yet about its “toxicity’’ or “impacts on fish,” according to a spokeswoman for Environment and Climate Change Canada, a federal department.
From its source at Cowichan Lake, the river flows for 30 miles across southeastern Vancouver Island, in one of the most fertile areas in Canada, past forests once full of towering cedars and Douglas firs, before draining into the Salish Sea. The Cowichan was the perfect habitat for chinook, chum and coho salmon, which could gorge on insects and swim in cool water shaded by trees.
“The river and everything within the river are considered part of our family,’’ Chief Hwitsum said. “And it’s our corresponding responsibility to look out for and take care of it.’’
Logging began in Cowichan Valley after the arrival of European settlers in the mid-19th century, and continues to this day. In the 1950s, a weir was built at Cowichan Lake to provide water storage for a paper mill, storing and releasing water during the dry months.
Residents in their 60s and older recall seasons of steady rain that fed the Cowichan and its tributaries, and cool, often cloudy summer months that kept the waters favorable for young salmon and trout. Some remember jumping off an old railway bridge nicknamed “Black Bridge’’ into the river — at a spot where the water might now be a foot deep.
Logging has felled many old-growth giant trees that kept the river and valley cool and that helped absorb rainfall that was gradually released into the river, experts say. Now rains have become irregular, often dumping huge amounts of water that cannot be absorbed into the soil. Snowpacks are melting sooner because of warming weather, leaving less water for the river during summer.
Joe Saysell, 75, a fishing guide who has lived his entire life along the river, said that the Cowichan’s shape has morphed in his lifetime, becoming wider and shallower, its bottom covered increasingly with gravel and less with the medium-sized rocks under which fry can feast on insects and hide from predators.
As a heat wave in mid-August brought days with temperatures in the mid-80s to the region, Mr. Saysell said, “The poor fish are just baking.”
Mr. Saysell, a retired logger and founder of the Friends of the Cowichan, a private organization formed to protect the river, was one of the first to see the dead fry last month after he was alerted by a friend swimming in the river with his daughter.
“This river is in the emergency room with a pile of doctors trying everything they can to keep that patient alive,” he said.
This summer, to conserve water amid severe drought, water release from Lake Cowichan was restricted to the lowest level possible. About 10 days before the dead fry were found, the flow of water in the river was reduced by more than a third.
The decades-old weir is incapable of providing sufficient water in the era of climate change, said Mr. Rutherford of the Cowichan Watershed Board.
In the past, the Cowichan River went through periods of drought but was always able to regenerate. Today, that is no longer possible, said David Anderson, who served as a federal minister of the environment two decades ago and is a member of the board.
“Nature does correct itself, but it can’t correct itself where man is substituting himself for nature and making decisions inimical to any possible recovery,” Mr. Anderson said. “We’re in a different world. We’re simply taking too much out of the environment worldwide.”
Source: NYTimes Science