Back to School by Art Butts, Fisheries Biologist, Idaho Department of Fish and Game - Southwest Region
As we head into the late summer, parents and kids become preoccupied with getting "back to school." For many of us at Idaho Fish and Game, late summer is a time when we become preoccupied with schools of another kind – schools of kokanee that is, beginning to ascend many of our local rivers.
Kokanee are miniature forms of sockeye salmon that spend their entire life in freshwater. They mature at two to three years of age, when they turn red and take on the spawning characteristics of their ocean-returning relatives. Males develop elongated hooked jaws and humped backs. Females remain slender except for their bulging abdomen full of eggs.
Idaho is home to both early and late-run Kokanee. Early-run Kokanee spawn in August and September; the Kokanee die soon after spawning, their bodies providing valuable nutrients to sterile spopulations around Boise are of this variety. Late-run Kokanee spawn in November and December. Spawning Kokanee either migrate into a lake tributary or, in some cases, spawn on the lake shoreline. Like their anadromous brethren, Kokanee tream environments. This boosts the productivity of the stream food web: more algae grow more aquatic insects for their progeny and other fish to feed upon.
Close to Boise, people travel to Mores or Grimes Creeks or the South Fork Boise River to witness this spawning exhibition. The bright red fish dig redds (egg nests) in the stream gravel and fight off competitors for mates or prime redd locations. Kokanee fishing during these spawning runs is a popular activity. However, spawning kokanee can be finicky as they are more interested in spawning, rather than eating. Silver spinners or orange-colored flies are popular offerings. Early in the run, kokanee offer good table fair with many people preferring to can or smoke the fillets. As spawning approaches, Kokanee become poor table fair as their muscles begin to deteriorate. Even late in the spawning run, aggressive and territorial males will still strike lures and flies. In Idaho, there is no snagging season for game fish, including kokanee, and any fish not hooked in the mouth or jaw must be released.
Kokanee fishing is becoming more popular throughout the western United States. A decade ago, Kokanee fishing might have been too specialized for most. It was a sport best suited for those persons with unlimited patience and willing to spend all day trolling. Now, Kokanee are on the cover of popular angling magazines. Websites and social media report on all the latest fishing techniques, news, and gear. Larger sections of tackle aisles are filled with specialized kokanee gear. Better gear and more informed anglers have led to higher catches.
No better example of the increase in Kokanee popularity exists than the one found right here in the Treasure Valley. The nearby Kokanee populations at Arrowrock and Lucky Peak Reservoirs are among the best in the west for catch rates and fish size. In 2011, anglers made around 66,000 trips and spent almost $4.8 million in fishing-related expenses at the two reservoirs. An increased statewide demand for the fish is reflected in the number of Kokanee stocked by Fish and Game. Just a few years ago in 2010, the department stocked 1.4 million Kokanee into 13 lakes. In 2014, 2.4 million Kokanee were stocked into 17 lakes.
Kokanee management can be difficult and is focused on finding a desirable balance between catch rates and fish size. Enough spawning fish are needed to seed a new year class, but not so many that members of the new year class become stunted. Kokanee exhibit a density-dependent relationship between fish growth and lake productivity. When adult Kokanee are small – say less than 10 inches – there are likely too many Kokanee. Vise-versa, if adult Kokanee start exceeding 20 inches, there are likely too few Kokanee to provide desired catch rates. Finding the balance between growth and density is tricky business and specific to each water body.
The source for most of Idaho’s hatchery Kokanee is Deadwood Reservoir, about 45 miles east of Cascade, Idaho. Early each August, a fish weir is constructed across the Deadwood River, and during the next four to six weeks, Kokanee are trapped and spawned at the site. Fertilized eggs are then flown from a nearby backcountry air strip to Cabinet Gorge Hatchery in Clark Fork, Idaho.
Fertilized Kokanee eggs need cold, clean water to survive and develop to hatching. The flight costs are offset by increased egg survival and reduced spawning days at the weir. After around 45 days, developing eggs are then transported to Mackay State Fish Hatchery. Here, the warmer water helps Kokanee grow quickly (three to six inches) for stocking the following spring.
Fish and Game biologists use a combination of methods to track Kokanee populations. This includes trawling, gill-netting, sonar, water quality, and creel surveys. Biologists can increase populations by stocking Kokanee or allowing more adult fish to ascend spawning streams. On the other hand, biologists reduce kokanee populations by limiting spawning numbers, increasing angler bag limits, and stocking predatory fish such as Fall Chinook.