Kokanee salmon, a unique freshwater form of sockeye salmon, complete their entire life cycle within inland lakes and their tributary streams. Unlike their ocean-going relatives, these fish undertake distinct migrations and transformations in freshwater environments.
Typical Spawning Season
Kokanee salmon typically begin spawning migrations in late summer, extending through fall. This timeframe commonly spans from September into December, depending on the specific geographic location and local population. For example, some populations may start spawning in late August and continue through October, while others might exhibit later runs into November and December. Variations in elevation and climate across their habitat range contribute to these differences in exact timing.
Environmental Cues for Spawning
Kokanee spawning is linked to environmental signals. Decreasing water temperatures serve as a primary trigger, often falling below a threshold of 55 degrees Fahrenheit. Shortening daylight hours, known as photoperiod, also play a role in initiating the physiological changes required for spawning. These combined environmental cues stimulate hormonal shifts within the fish, prompting their migration from open lake waters towards their designated spawning grounds.
The Spawning Ritual
As the spawning season approaches, Kokanee salmon undergo a striking transformation, migrating from the deeper parts of lakes towards natal streams or gravelly lake shores. Their silvery bodies change dramatically, turning a vibrant red, with males often developing dark green heads and black snouts. Males also develop a pronounced humped back and a distinct hooked jaw, called a “kype,” along with elongated teeth, which they use in competition for mates.
Upon reaching the spawning grounds, female Kokanee use their tails to excavate depressions in the gravel, known as redds. This involves “nosing” to test gravel, followed by powerful tail movements to displace sediment. Once a redd is prepared, the female deposits her eggs, which are then fertilized by one or more attendant males. Following fertilization, the female carefully covers the eggs with gravel.
Life After Spawning
Kokanee salmon exhibit a reproductive strategy known as semelparity, reproducing only once before dying. Shortly after completing the spawning process, both male and female Kokanee succumb, their bodies returning nutrients to the aquatic ecosystem. The eggs, now safely buried within the gravel redds, remain protected throughout the colder winter months. Over time, these eggs develop, hatching into tiny fish called alevins in late winter or early spring. These young fish, nourished by a yolk sac, eventually emerge from the gravel as fry and are swept downstream into the lake.