(The following story by Scott Simpson appeared on the Vancouver Sun website on July 11.)
VANCOUVER, B.C. — The recovery of the Cheakamus River may be more rapid and vigorous than anyone imagined when a catastrophic chemical spill wiped out fish in the Squamish-area stream in 2005.
Fisheries research since the spill confirms that a CN Rail derailment that spilled 40,000 litres of caustic soda into the stream on Aug. 5, 2005 played havoc with juvenile populations of migratory salmon and steelhead, as well as full-time river residents including sculpin and stickleback.
At least 500,000 fish died, the B.C. Ministry of Environment estimates, including 90 per cent of one-year-old chinook and steelhead, and 50 per cent of two-year-old coho.
However, researchers are also reporting some inadvertent benefits from the disaster, which will be reviewed in more detail in a report on the CN derailment to be released today by the federal Transportation Safety Board.
It appears that the elimination of so-called coarse fish made life easier for subsequent generations of salmonid hatchlings to thrive — removing threats of predation and easing competition for food.
For example, a record number of chum fry survived to migrate out of the Cheakamus this spring.
University of B.C. fisheries researcher Josh Korman said in a telephone interview on Tuesday that, anecdotally, his own in-stream snorkel surveys are turning up swarms of newborn and one-year-old steelhead.
Again, an absence of predators and rivals — including older juvenile steelhead wiped out in the spill — gets the credit.
That’s not all — Korman said there has been an apparent upswing in ocean survival over the past three years for steelhead migrating out of the river.
The small number of fish that escaped the 2005 spill could be thriving out in the ocean — and surviving in greater numbers than nature typically allows.
That would set the stage for a steelhead population recovery in just a couple of generations — 10 years — compared with the 50-year timeline some biologists had originally feared.
Korman has unpublished data on the steelhead return to the Cheakamus last spring showing the run was unusually strong and he suspects favourable ocean conditions were the reason.
Korman said the full effect of the spill won’t be discerned until at least 2008, and more likely 2009-10. That’s when Cheakamus steelhead that survived the spill as juveniles are scheduled to return as spawning adults.
The return for those generations could be negligible, but Korman said there is room for optimism based on what’s happening in the river and ocean.
“What we are seeing now are adult returns, the fish that were out at sea the last two years and were not exposed to the spill. Last spring’s return was the best we had on record,” Korman said.
Juvenile offspring from spawning generations that were not exposed to the spill are also thriving.
“I’ve snorkeled in there at night and looked at juvenile fish. I’ve seen fish densities in other rivers, and I can say that the steelhead densities in the Cheakamus are exceptional right now for parr and fry.”
B.C. Environment Minister Barry Penner said the government was “extremely disturbed” by the impact of the spill.