Spawning numbers see increase
The good news is the highest number ever of shore spawning Okanagan Lake kokanee returned this fall to lay their eggs before dying.
The bad news is there was the lowest return of stream spawning kokanee since the crash in kokanee populations in the big lake in the early 1990s, when only 6,000 to 7,000 were counted.
This fall, only 18,000 stream spawners returned to lay eggs, while 276,000 shore spawners flooded the shorelines around the lake, reports Paul Askey, fisheries stock assessment biologist with the ministry of forests, lands and natural resource operations in Penticton.
“They’re probably almost saturating the lake,” he commented. And, they could be giving the stream spawning kokanee stiff competition for available food in the lake too.
Askey says in some parts of the lake the shore spawners are like “urban kokanee. They’ve become hard to count amongst the docks jutting out into the lake,” he commented.
However, the size of the shore spawners is small. Most are around 23 centimetres in length, so they make great rainbow trout feed, but they’re not much sought-after by anglers. On the other hand, the stream spawners range in size, but average about 26 centimetres. Some can be 50 centimetres and lots are longer than 30, so they’re much more attractive to anglers.
He figures they range in age from three to five years, while the shore spawners are two or three.
With that number of kokanee in the lake, Askey is satisfied that the lake is doing well sustaining them, a concern that resulted in creation of a 20-year action plan in 1995 to work on bringing their numbers back up again.
One of the factors cited in the studies done as a result of that plan was the introduction of mysis shrimp in 1965, as feed for rainbow trout. It was found instead that the introduced crustacean actually out-competed young kokanee for feed in the lake.
“Mysis definitely knocked back the lake’s productivity, but they do show up in kokanee bellies,” commented Askey.
He wonders if kokanee are beginning to learn how to use them in their diet, now that their numbers are back up.
The numbers emerging from the spawning channel constructed in 1988 in Mission Creek, in the regional park off Springfield Road, are 36 per cent of the creek’s total numbers, while in 2010 they represented 42 per cent and in 2009 46 per cent. In 1992, the channel averaged 30 per cent of the creek’s returns.
However, in 1991, more than 94,000 kokanee returned to Mission Creek, while this year the total was a tenth of that, just 9,000. However, in 1998, only 1,000 were counted.
Although Mission Creek contributes the largest numbers of kokanee stream spawners into Okanagan Lake, numbers have also been low in other streams this fall, with 2,000 each counted in Peachland and Penticton Creeks, 1,200 in Powers Creek, and 600 in Trepanier Creek.
Although a decision hasn’t yet been made, Askey expects a summer kokanee fishery will be opened again in 2012 on Okanagan Lake.
A ban on fishing for kokanee was instituted in 1995 because of the crash in their numbers.