The Daily Courier
Sunday, September 18, 1994
The number of kokanee in Mission Creek is unusually low for this time of year, but it’s too early to conclude the spawners are in trouble.
Preliminary tests show the number of kokanee in the spawning channel of the creek was about 700 on Thursday. At the peak spawning time in late September last year, there were about 6,000 fish.
“Mission Creek appears to be unusually low for this time of year,” said Brian Jantz, a regional fisheries technician. “We don’t know if they’re just late or they’re not coming.”
Despite the lower count, the severe drop of more than 1.3 million sockeye salmon in the Fraser River this season hasn’t been reflected in the streams flowing into Okanagan Lake.
Peachland Creek is about normal for this time of year. Scientists counted nearly 1,000 kokanee on Thursday. “It should have a healthy run,” said Jantz.
Last year, officials counted the lowest number of stream-spawners (90,000) and shore-spawners (20,000) in and around Okanagan Lake in years. Mission Creek saw 15,000 stream-spawners last year, down from 36,000 in 1992.
Stream-spawners around the lake tend to fluctuate between 75,000-150,000 from year to year, but the shore variety, which spawn in late-October, have been steadily declining.
Last year scientists counted 20,000 in Okanagan Lake, well below the peak of 560,000 reached in the early 1970s. “We don’t know why,” said Jantz. “It’s something we’re quite concerned about.”
Several environmental pressures may have contributed to the drop, including habitat destruction, fluctuating lake levels, and more anglers fishing the lake.
Adding to the stress on the shore-spawners is an increase of predators like rainbow trout, which eat one- and two-year-old kokanee, and competitors for food, such as carp, suckers and burbot (also known as freshwater ling).
“A number of these factors could be at work, but it’s hard to pin down,” said Jantz.
The biggest pressure on kokanee, ironically, is from a food source officials introduced in the mid-1960s as a way to improve kokanee stocks, a tiny freshwater shrimp called Mysis.
“The (Mysis) populations are at extremely high levels,” said Jantz. “They compete for plankton, as do the kokanee fry.
“The plan backfired. They turned out to be competition in the kokanees’ early life stages.”
The stream-spawners have fared better, in part because sporting clubs have enhanced stream beds so eggs can mature better. Jantz is confident the numbers will be as good or better than last year, despite the early poor showing in Mission Creek.