Thousands of adult pink salmon died last week when the lower portion of the Mamquam spawning channel ran dry, stranding them in shallow puddles below a point where the water level still supported live spawners.
Squamish Streamkeeper John Buchanan, who rescued a couple dozen female salmon that were still living after the sudden de-watering last Thursday (Sept. 5), said he thinks a decision by those at the nearby Squamish Valley Golf Club (SVGC) to turn the pumps on and water early that morning may have contributed to the event.
A biologist with the federal Department of Fisheries and Oceans (DFO) isn't so sure about that claim, however.
Buchanan said he believes a pond used by the club as a water source for the course is connected to the aquifer that helps feed the spawning channels. Turning on the pump could have caused a nearby stretch of the stream to run dry, he said.
“You drop the water levels here even two inches and it can have a devastating effect,” Buchanan said after rescuing some live salmon, then cutting open a few recently deceased female fish and finding them with full sacs of eggs — indicating they hadn't yet spawned when they died.
After a similar occurrence last year, Buchanan was one of the first people to go in and rescue stranded coho fry.
“The guys [Streamkeepers] are used to coming down here and salvaging fry, but this [last Thursday] is the first time I've done this with adult salmon,” he said.
Keith Strom, SVGC superintendent, said that after a large rain event on Aug. 28, golf course officials didn't water again until Sunday (Sept. 8), after the de-watering. He said circumstances lead him to believe there's little or no connection between the level of the pond and the amount of water in the stream.
“If our pond is full and their stream is running dry, it should be obvious that either they're independent or they're dropping at different intervals,” Strom said.
Matt Foy, section head of the resource restoration component of DFO's Salmon Enhancement Program, on Tuesday (Sept. 10) said this isn't the first time the channel, which was constructed in 1983, has run dry in a similar manner — i.e. with sufficient water close to a source pond upstream but not enough in the lower reaches to support struggling salmon fry.
Foy said the Mamquam aquifer that feeds the channel has some unusual characteristics.
“There's been a longstanding issue with that channel, that it flows strongly all winter and spring, and in a typical year it starts to dry out from the bottom end, up. The upper end of that channel is deeper in that aquifer,” he said.
“What that means is when the aquifer is draining away downhill, the groundwater channel at the upper end is deeper below the water table, but the lower end of the channel might be above the water table.”
This year's situation is unusual in at least two respects, he said — one, the drier-than-usual summer weather and two, the enormous pink salmon run in the Squamish-Cheakamus River system, Foy said.
The Aug. 28 thunderstorm caused river levels to rise rapidly, followed by a relatively dry stretch. Spawning pink salmon made their way into the Mamquam channels after the storm and while some swam into side channels unaffected by the de-watering, some obviously did not, Foy said.
The pre-spawn die-off “isn't what we'd like to see,” he said.
“We had these events conspire — a large pink salmon run, a shallow aquifer, the very dry summer, followed by a flood event and then the aquifer doesn't recharge and it dries out,” Foy said.
Some of the eggs that were laid before the channels went dry — even some of those now sitting in shallow pools — will likely hatch if and when water levels recharge, Foy said.
Foy said there's never been a full study of how the aquifer works. In 2005, DFO and local fisheries groups proposed such a study but the grant money for such a study hasn't yet been secured, he said.
For now, a limited, preliminary study of the aquifer is all they have to go on. It might be possible to alter the channel's design to prevent salmon from dying, but “we've been reluctant to do something with the Mamquam channel because it has been so productive, even aside from these problems,” he said. “So we're reluctant to go in and do any modifications without a much better understanding of what's happening with the aquifer.
“I think the issue just highlights why an aquifer study would be valuable to all the parties in the area — the golf course, the streamkeeper groups, people like ourselves. Just understanding it better would keep us all on the same page, because I think it's been viewed by all parties as a tremendous community asset.”