James Murray tells a story for a small crowd at the ORL Salmon Arm branch on Saturday, Feb. 25.

Column: Warming waters bad for salmon

By James Murray

Peering down into the surprisingly clear waters of Mable Lake, it was hard to know for sure just how deep the water was below the boat.

I knew I had to be in at least 15 to 20 feet of water.

What was unmistakable, however, was the number of fish holding just off the bottom on both sides of the drop-off. I was eager to get my line in the water but several hours of casting brought not one single bite. I could see them but I couldn’t catch them.

As temperatures continue to rise and water levels drop in many of B.C.’s lakes, rivers and streams, fish stocks throughout the province are coming under ever-increasing pressure. With continued warm weather, oxygen levels in many lakes are becoming depleted and fish are starting to hold in the cooler waters near the bottom. They are no longer moving in constant search for food, but rather simply staying relatively motionless, feeding only when opportunity arises, using up as few calories as possible.

As I sat in my boat, I began to wonder about the prospects this fall for Mable Lake’s salmon.

Research conducted by the United States National Wildlife Federation (Fish Out of Water: A Guide to Global Warming and Pacific Northwest Rivers) shows that a three degree rise in average August temperatures would cause up to 20 percent of the streams in the Columbia River Basin and coastal watersheds of Washington and Oregon to become too warm for most salmon, steelhead and trout. It only follows that rivers and streams in British Columbia would be similarly affected.

A recent Fisheries and Oceans Canada report indicates water temperatures in the northeast Pacific region are approximately 3 C above normal.

“Record warm ocean temperatures combined with low, unusually warm rivers pose a double threat to B.C. salmon, prompting the DFO and government officials to curtail some fisheries. The reduced fisheries are part of a cautious approach to ensure a healthy number of salmon return to river spawning grounds.”

The report goes on to say warm water temperatures are also having an effect on some of the food sources that salmon normally eat. As a result, the younger salmon that will swim to sea after this warm spell may not survive, or might return thinner and weaker. The DFO is also expecting there to be fewer numbers coming back in the next one to three years.

Scott Hinch, a professor of fisheries conservation at the Pacific Salmon Ecology and Conservation Laboratory at UBC, says he expects temperatures will continue to rise over the course of the summer.

“The Fraser River, for example, could peak at 19 or 20 degrees, and that, plus low flows, could impact whether spawners could get to spawning grounds.

By the time you get to 20 degrees, many fish are suffering mortality because they’re suffering from low energy reserves. They have to work a lot harder when temperatures are higher and they have a finite amount of energy they’re bringing with them.”

“They’ve come into an environment with poorer fish food and a lot more predators,” he says. “We anticipate this will affect their survival, certainly their growth and their survival.”

Low rainfall in the past few months, coupled with sustained warm temperatures, is certainly cause for concern.

Water levels in the Fraser River systems are already lower than normal – more typical of levels normally seen in the latter part of August – and it is raising concerns about the health of the salmon runs.

Previous DFO research has shown the swimming ability of migrating salmon starts to decline when water temperature hits 18 C. In previous, similarly hot summers, 40 to 90 per cent of Fraser River salmon have died before they were able to spawn.

Low water levels combined with warm dry weather has resulted in drought-like conditions in several regions of the province, especially in central and southern B.C. One can only wonder what is in store for everyone in the province over the next month or so. Forest fires are raging out of control, and people’s lives and livelihoods are being affected by both the fires and the continued hot weather.

So is the future of the fish in many of our lakes, rivers and streams. Salmon stocks, it would seem are in peril. What we need is rain and lots of it. Please let it rain.