Counts of spawning kokanee on Wood Lake this fall have confirmed there’s only 10 per cent the number of fish there were two years ago.
Reason for the crash in the kokanee population has not been pinpointed, reported stock assessment biologist Paul Askey with the natural resource operations ministry.
However, routine water profile monitoring done on the lake in September, 2011 indicated anoxic conditions (lack of oxygen) in the bottom eight to 10 metres of the lake, and temperatures of 20 C above that—too high for kokanee habitat.
As well, he said there were reports of the occasional dead kokanee found in the lake that year, and spawner numbers were down from the 20,000 in 2010, to 6,000 in 2011. Last fall, only 2,000 were counted.
Water conditions were monitored throughout the summer this year by volunteers from the Oceola Fish and Game Club, and they were excellent, so the same water condition didn’t repeat itself, he noted.
But, he said Wood Lake has become known as being a nutrient-rich lake that’s a great producer of big fish, and what may have happened is it went over the ‘tipping point,’ said Askey.
“All the same factors that make it a great lake also put it at great risk,” explained Askey. It’s high in nutrients, has good access so it gets a lot of fishing pressure, it’s urban, so subject to runoff or releases of various materials, and it’s low in the valley bottom so it is subject to high summer temperatures.
Because of numbers the past couple of spawning seasons, Askey is not hopeful that the next few years will be much better.
Although, he said it will be interesting to see if that few spawners can produce juveniles. The size of fish was up this fall, so lots of eggs were deposited, he noted, and fish do tend to compensate for low populations.
However, both water quantity and quality seem to be issues, he said.
The Habitat Conservation Trust Foundation is supporting work to supply water for spawners in Middle Vernon Creek, and the increased flushing that would occur with higher flows could help in-lake conditions as well, he said.
“I hope we can turn Wood Lake around,” he added.