1.1 million salmon en route, 300,000 could die before arriving
By Larry Pynn, Vancouver SunOctober 17, 2011
An estimated record run of 1.1 million late-run sockeye are destined for the Harrison River system in the upper Fraser Valley.
"It's a very good run," Mark Saunders, division manager for salmon and freshwater ecosystems, said in an interview from the Pacific Biological Station in Nanaimo.
"This is one of the [late-run] populations ... that is doing extremely well. We're expecting a very high escapement on to the grounds."
The record run of 1.1 million Harrison sockeye this year - an estimate based on migrating fish counted at Mission - compares with 389,000 sockeye in 2005, 169,000 in 2006, 128,000 in 2007, 6,750 in 2008, 307,000 in 2009, and 761,000 in 2010.
As many as 300,000 fish could die en route to their spawning grounds, he said.
Despite the large-scale dieoff, the federal fisheries department says such events are not unheard of and it remains pleased with the returns and the numbers expected to successfully spawn.
Temperatures, water flows, fat reserves as the salmon leave the ocean, stress, and disease are among factors that could "conspire to kill them on route," he said.
Sockeye in recent years have also been entering fresh water up to several weeks earlier than normal, which could put them at increased risk.
"Once they're in fresh water, they don't eat and have to run on their reserves," Saunders said.
"A lot of things have to go right for any given salmon, right from the time it migrated out until it comes back, to get them back on the spawning ground."
Accurate en-route mortality rates are not available every year, but federal fisheries estimates 27 per cent of the total Harrison run are expected to die before spawning this year, compared with 27 per cent in 2007, 81 per cent in 2008, and just three per cent in 2010.
The peak of Harrison-bound sockeye travelled past Mission in late August, but won't start spawning for about another week, with federal fisheries staff on the ground to monitor success, Saunders said.
Alexandra Morton, who for years has warned about the dangers of salmon farms transferring disease to wild stocks, said she believes farms have contributed to en-route mortality since 1995.
But she said the Harrison's stocks seem to be bucking the trend among sockeye destined for the Fraser River system, perhaps, in part, because of their migratory routes at sea.
"They are doing phenomenally well," she confirmed.
Morton said she is conducting her own tests on the Harrison fish and urged the federal government to fund greater research into causes of en-route mortality.
"We need a huge push to determine why these fish are dying," she said.
"Everything must be thrown at this. It's very important to get to the bottom of it."
lpynn@vancouversun.com© Copyright (c) The Vancouver Sun
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