"...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...."
I don't know, if they immediately dismiss the pollution and ascribe the fish kill to climate change, wouldn't someone measure the water temperature and compare it to previous years? I kept reading hoping that there would be some actual data on river temperatures but nothing.
I don’t think investigators are immediately dismissing any possible cause(s). Since this is my home river, I’m trying to keep current on more news about this terrible loss. Here’s a recent article in the Vancouver Sun (BC):
The Cowichan’s decline “is the death of 1,000 cuts.”
vancouversun.com
I checked river water temperature records online for this time period, and noted it was about 21 to 23 C. Pretty high for coldwater fish.
High water temps have a double whammy effect on fish. The higher the water temp, the less oxygen it holds. And high water temps also increase fish’s metabolism; meaning fish have a higher demand for oxygen, but there’s less oxygen in the water.
Another cause of low dissolved oxygen is organic pollution, which uses up oxygen as it decomposes. We’re talking here about the minimally-treated sewage discharged from the town into the upper river.
They are also considering possible toxins dumped into the river. The river is overcrowded with people swimming, camping, and boating in summer, especially in yet another recent record drought. Maybe somebody did something really bad.
Since this situation is of interest to American PNW anglers, and even as far away as New York City, I’ll post any news that I find.
www.nytimes.com
