Ask Zimo: Deadwood's popular kokanee are complicated fish

pzimowsky@idahostatesman.comJuly 10, 2014 

Q: What's the deal with Deadwood Reservoir? The kokanee have been pizza-topping size for two years straight now. I was just there for a week - not a single fish over 8 inches was caught.

RYAN GUSTAFSON, via email

A: The one thing about kokanee: The more fish in a lake or reservoir, the slower they grow, and that's the main problem at Deadwood Reservoir.

When you have too many fish and not enough food, the fish can easily become stunted. Deadwood Reservoir's supply of zooplankton, which the fish feed upon, also is not that productive.

Idaho Fish and Game is aware of the problem with kokanee at Deadwood and is working on it.

"We have been working on getting the size of maturing kokanee at Deadwood Reservoir back up to at least 12 inches," said Art Butts, southwest regional fishery biologist with Fish and Game's Nampa office.

The reservoir, located about 15 miles north of Lowman, has always been a popular trout and kokanee fishing hole. Anglers pride themselves on crashing through snowdrifts to be the first ones there for the season. They drag their boats on some of the worst washboard, dusty (or muddy) forest roads to get up to the reservoir and enjoy the fishing.

Besides being a fishing hole, Deadwood also is important to the state in providing a source of spawning fish for eggs to supply most of Idaho's hatchery kokanee.

The agency operates weirs on the Deadwood River and Trail Creek, where biologists trap the spawning fish.

In addition, biologists also limit the number of fish going past the weirs to reduce the number that spawn upstream and, in turn, reduce the number of young fish returning to the reservoir.

"We are still learning about how many we can let go up the tributaries to seed the next year class, while also produce fish of a decent size that provide a good sport fishery," Butts said.

Another factor to the rescue at Deadwood is fall chinook salmon.

Fish and Game has stocked 5,000 chinook annually in the reservoir since 2009 to feed on the kokanee and provide a sport fish.

"They have been growing like crazy, and anglers have been very happy," Butts said.

Three-year-old chinooks are 24 to 28 inches, and the four-year-olds are more than 32 inches.

Fish and Game receives fishing reports from Deadwood, and while some anglers have bad luck and catch younger fish, others have been doing quite well, not only on kokanee, but trout as well.

Some avid Deadwood anglers reported Monday they spent the holiday weekend at the reservoir and caught 89 kokanee in the 10- to 11-inch range. The fish were bigger than last year, anglers reported.

That's a positive sign, and Fish and Game hopes to see its goal of 13-inch kokanee by next summer.

Pete Zimowsky: 377-6445, Twitter: @Zimosoutdoors

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