Where have all the kokanee salmon gone?
July 17, 2012
By Dallas Cross
For 5 million years, an ancient class of salmon has been swimming in lakes and streams once connected to the Pacific Ocean. They are kokanee, a small species of freshwater salmon.
Kokanee live in Lake Sammamish and spawn in its creeks. Their scientific name is Oncorhynchus nerka. It is a combination of hooked-nose in Latin together with a complex, Latin-Polish name for red salmon. They share the nerka name with their ancestral, but genetically distinct, sockeye salmon. The name, kokanee, comes from the Okanagan-Salish language and means red fish.
Lake Sammamish kokanee embrace their red fish name when they return in November through January to their birth creeks to spawn. In the lake, they are mostly silver with small scales, not spotted like trout, and have a distinctively forked tail. At spawning time, the bodies of males turn a bright red with green heads and a hooked nose. The females’ bodies turn red with a faint green stripe.
Spawning pairs seek gravel beds in the same streams where they were hatched. In these streams, they move gravel around making redds in which the female lays eggs to be fertilized by the ever-attendant male. The eggs incubate in the gravel redds for three to four months during which an alevin with an egg sac forms. Alevin then absorb the sac and mature into kokanee fry. The fry wait for a stream temperature of about 52 degrees and a dark night to leave their gravel beds and make a run downstream to the lake.
What do kokanee eat?
In the lake, the kokanee fry start feeding on small animals collectively called zooplankton. In Lake Sammamish, a zooplankton called daphnia, or water flea, is the main diet of kokanee fry and also a significant portion of the diet of mature kokanee. The daphnia in turn rely on algae for their food.
May is significant in that it is when populations of algae and grazing daphnia increase in response to light and temperature. It is also the month in which kokanee fry complete their journey to the lake to start feeding on daphnia. Mature kokanee also eat insects and the larger ones occasionally prey on minnows such as coho fry.
Why are only a few left?
Kokanee in Lake Sammamish are threatened. Tens of thousands ran in the creeks feeding the lake in pioneer times. Recent counts of spawning kokanee in the fall and winter are in the hundreds at best, and often only in the teens. Most notable is the absence of spawning kokanee in Issaquah Creek, the main tributary that feeds the lake.
The development of the Issaquah Salmon Hatchery in the 1930s doomed the early run of kokanee in Issaquah Creek with a diversion dam and fish weirs to prevent kokanee returning to their traditional breeding gravels. This was to prevent them from carrying fish diseases upstream into waters supplying the hatchery. Hatchery personnel were instructed to remove any remaining spawning kokanee and this contributed to the early run in Issaquah Creek run being officially declared extinct. But there are still kokanee in the lake.
How have they survived?
Fortunately, some kokanee spawn in the lower reaches of several small creeks feeding Lake Sammamish: the Laughing Jacobs, Pine Lake, Lewis and Ebright creeks have returning runs of kokanee. Also, it is suspected, but not affirmed, that kokanee may spawn on beach gravel beds in the lake.
Why are lake kokanee small with spawning creeks available?
Food scarcity does not appear to be a factor as mature kokanee in the lake are much larger than kokanee in other lakes. Predation by birds and kokanee-eating fish, such as cutthroat trout, northern pike minnows, perch, bass and coho salmon, does reduce their numbers.
The biggest problem has been shown to be the lack of gravel beds for spawning and smothering sedimentation of the few that remain during floods when eggs are developing. Only short reaches near the mouths of the remaining spawning creeks are suitable and accessible. Several creeks now have barriers such as culverts or dams, or have been channeled or diverted to ditches without gravel suitable for redds.
Kokanee survival is a probability game scored in reduced numbers of kokanee fry that hatch and return to the lake. For several years Bellevue-Issaquah Chapter members of Trout Unlimited have volunteered to spend nights counting retuning fry in Lewis Creek. They have recently added Ebright Creek to their census taking. Fluctuations in annual totals of returning fry range from hundreds to only a single fry.
This information, together with diminished spawning kokanee census figures, has prompted King County to form a Kokanee Work Group to define the problem and come up with actions needed to restore kokanee in Lake Sammamish. Its goal is restoration to levels that can again sustain recreational fishing.
Exciting progress has been made toward supplementing kokanee runs in the remaining spawning creeks. Plans are under way to restore spawning habitat and re-establish kokanee in Issaquah Creek. These are products of the Kokanee Work Group working with the state Department of Fish and Wildlife, conservation groups, local Indian tribes and private citizens. The prospect of a hopeful future for kokanee will be addressed in a coming article.
Reach Dallas Cross at FishJournal@aol.com or www.fishjournal.org. View previous articles and comment on this column at www.issaquahpress.com.