Troubled waters for Kluane kokanee
In 1996, the spawning bed at Sockeye Creek in Kluane National Park was red with kokanee salmon. Almost 8,000 of the land-locked fish were burrowing into the stream's gravel bottom, the most that had ever been counted.
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Not as many kokanee salmon are spawning in Kluane National Park now, and experts are looking for the reason for the decline.
(photo: Kluane National Park and Reserve)
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Over the next few years, the number of spawning fish dropped, but the decrease did not seem like anything to worry about. Then in August, 2003, the Kluane wardens could find only 160 fish. The news was worse this past summer; 53 salmon were counted in the lake.
Something has obviously changed in the world of these kokanee salmon, and -- while there are lots of theories -- no one knows why.
The ancestors of these fish were sockeye salmon that descended the Alsek River and spent several years feeding in the Pacific Ocean before returning upstream. At some point, the salmon in the lakes quit returning to the ocean and switched to spawning in freshwater.
Over the centuries Lowell Glacier has surged powerfully several times, completely blocking the Alsek River with ice, so the salmon's change in routine is probably linked to one of these episodes.
Kokanee in the Kathleen Lake system rarely weigh more than one kilogram and measure about 50 centimetres in length. Kokanee are found in many parts of western North America, but the Kluane kokanees are one of the few -- perhaps the only -- naturally occurring population within a Canadian national park. They stay in deep water for most of the year, but in early June, when they are in shallow water, anglers eagerly seek them out.
Park staff began counting the numbers of spawning kokanee back in the 1970s, and have been keeping a close eye on this unique population of fish ever since. People are not allowed to camp by Sockeye Lake, or to fish there, though they may fish in Louise and Kathleen Lakes, which are both downstream of Sockeye.
To avoid introducing parasites or disease to the fish, fish parts cannot be used as bait. People were allowed to catch two fish per day, but now any kokanee caught must be released.
A working group of various specialists started meeting last winter to try and figure out what the problem might be, and what studies should be done. Some of this work has already started.
Last spring and summer, stomachs from the lake trout caught by sport anglers were collected to see whether these predatory fish might be gorging on kokanee. Technicians also checked the stomachs of other fish caught by sport anglers, to see what they were eating. The heads of these fish were analyzed to determine their ages.
The Yukon government conducted a creel census, counting the number of sport anglers and what fish they were catching in Kathleen Lake and River. There are plans to analyze climate data and look for links between changes in temperatures and fluctuations in kokanee numbers.
They are also looking at what the kokanee eat. "They tend to be plankton eaters and one hypothesis is that maybe the type of plankton has changed or maybe with global warming, the fish are emerging sooner than food is available," says Lloyd Freese, a Kluane warden and member of the kokanee working group.
Normally the kokanee spawn in August and hatch in January or February, but stay down in the gravel until spring when they emerge and start feeding. "If, for whatever reason, their timing does not coincide with the plankton bloom, that could be a problem," explain Freese.
Other theories are based on the spruce bark beetle infestation that has decimated the forests of mature white spruce trees in Kluane. In the Sockeye Lake area, many of the trees are already dead and their needles now carpet the forest floor. The forest canopy is more open than before, which may have increased temperatures in the area, leading to other changes in the water.
The dropped needles themselves could be causing problems. "When needles from the trees fall off and end up on the ground, many of them, or the residue from them, might be washed into the lake causing a change in the water chemistry or quality," says Freese, adding that potentially this could be yet another effect of the global warming trend that has allowed the spruce bark beetles to spread unchecked.
If worse comes to worse, there is at least a backup for this kokanee salmon population. Hatchery-raised kokanee have been used to stock a couple of Yukon lakes, and there are kokanee in reserve at the Whitehorse Rapids fish hatchery.
The hatchery kokanee were first established for just this reason -- so that they could be used if the natural population crashed. "But before we worry about restocking, we want to try and figure out what has caused their demise in the first place, and even then we would have to discuss it with our partners and decide if it was just a natural way for the kokanee to go" says Freese.
- For more information on kokanee salmon in Kluane, contact the Kluane National Park and Reserve headquarters at (867) 634-7250.
