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Kokanee numbers dropping in the Okanagan
The numbers of Kokanee spawning in Wood Lake, one of the Okanagan’s most popular fishing spots, was down this year, as was the Okanagan Lake stock, but for different reasons.
According to provincial fisheries biologist Paul Askey, the number of Kokanee spawning in Wood Lake were only a tenth of the number counted two years ago.
“This year was really bad, just a couple of thousand fish by our index counts. As an example, two years ago there were 20,000,” said Askey. In the larger but less nutrient rich Okanagan Lake, the numbers were even more dramatic.
“We saw a pretty big drop in shore spawners, there was only 78,000 shore spawners and there was just shy of 20,000 stream spawners, which is also a low number, but we have been in that low range now for the last three years,” Askey said. “Last year was a 30-year high, there was 278000 fish, so it’s a big drop. But you don’t have to go very far back to find another low year, 2004 there was 46,000.”
Askey suggests a fish kill that occurred over the 2012 summer may be partly to blame, as well as this year’s spawning population having to compete for food with the much larger 2011 run.
“They are all competing for the same food in the lake, so that could definitely part of it,” said Askey. Okanagan Lake, he continued struggles a bit with nutrient content, while the high nutrient content that makes Wood Lake so productive may have contributed to a smaller run this season.
Large amounts of decomposing algae in 2011, he said used up a lot of the oxygen in the lake, leaving all but the top eight metres or so oxygen starved. Temperatures at the top layer hover at 20 C and higher, too warm for the Kokanee that were now being squeezed into it.
“That’s pretty stressful for Kokanee, so we saw the spawn numbers go down,” he said, noting that it affected the 2011 run, older fish getting ready to spawn, than it did the 2012 run.
“It looks like they took a hit, though not as big as this years, which were smaller fish at that time,” said Askey. “So that went down a lot and we expect it to stay that way for the next couple of years and then bounce back in 2015 as long as the water quality stays okay.”
In Okanagan Lake, Askey would like to see numbers come up, especially among the stream spawners.
“Even though it was the shore spawners that went down, it is the stream spawners that are a concern. They have been consistently low since the collapse in the late 90s, where the stocks were on the brink,” said Askey. They came back, but shore spawners came back a lot stronger. There are fewer streams and they are very heavily impacted, like Penticton Creek. Some still hang on because there are the spawning beds that the fly fishers maintain. But that would be great to improve that stream.”
The biggest stream run on Okanagan Lake this season, Askey said, was at the Mission Creek spawning channel.
“There was 6,600 fish there, in that small channel,” he said. “All the other streams were 1000 or below, although Penticton Creek stood out as one of the winners this year at 1,700. That’s probably directly related to the fly fishers going in and changing the gravel regularly and cleaning.”
That shows, Askey said, that more rehabilitation of the streams feeding Okanagan Lake could increase the proportion of stream spawning Kokanee, strengthening the fishery in the lake.