The Rainbows Are Biting In C.J.

By Joe Kozfkay, Fisheries Biologist, IDFG, Southwest Region Mention the possibility of fishing at C.J. Strike Reservoir to any of Idaho's multi-species anglers, and their heads may explode. Too many possibilities and just too little time. Should you cast small jigs in the tules for crappie and bluegill, or retrieve a crayfish pattern crankbait near submerged boulders waiting for a smallmouth bass to pounce? Or would a largemouth bass engulf a topwater plug underneath some overhanging brush? And that's just in the shallows. Moving offshore could you go toe to fin with a gnarly, old channel catfish, or might you find a hungry school of yellow perch and catch them with some night crawlers fished near the bottom? And don't forget the behemoth white sturgeon that use the reservoir like a smorgasbord. The options are limitless. Now before somebody has a heart attack, slow down, catch your breath, and let's talk about just one aspect of this popular fishing destination, the rainbow trout. C.J. Strike Dam, built in the early 1950s, impounds the Snake and Bruneau rivers. Though rainbow and native redband trout spawn in the headwaters and tributaries of these rivers, nearly all rainbow trout found within the reservoir are produced in one of two Idaho Department of Fish and Game trout hatcheries in Nampa and Hagerman. Fish and Game has consistently stocked C.J. Strike since shortly after the reservoir filled. The reservoir offers unique circumstances that influence the success of rainbow trout stocking and the fishery. On the positive side, the water levels at C.J. Strike fluctuate very little, so even in drought years the reservoir is full. Also on the positive side, the reservoir is highly productive, especially the Bruneau Arm where abundant zooplankton, midge larvae, and other aquatic insects create an ideal forage base. Stocked rainbow trout gorge themselves on this abundance and grow rapidly. Rainbow trout stocked as 3- to 4-inch fingerlings in April will reach 14 to 15 inches by November, a remarkable growth rate compared to other systems in Idaho. On the other hand, life isn't always so pleasant for C.J. rainbows. The abundant bass, catfish, and pikeminnow don't hesitate to take advantage of the naivety of recently stocked fingerlings, and prey on them heavily, especially during the first week after stocking. Predatory fish with big enough mouths even chomp down on some of the 8- to 10-inch catchable rainbows. And don't forget the fish-eating birds. It can be a tough world for a newly planted hatchery trout. In high water years, rainbow trout may get free rides through the turbines or over the spillway. Though the survivors create a popular winter and spring fishery in the tail water, these fish suffer higher than average mortality rates and are lost from the reservoir population. To top it off, during low water years, water temperatures and oxygen levels in the reservoir may approach lethal levels for trout. So why bother? Well, simply put, under the right conditions fishing can be phenomenal. It turns out that the rapid growth rates can make up for the poor survival. And Fish and Game is continually adjusting stocking strategies to maximize the number of survivors. A recent evaluation conducted by Fish and Game personnel revealed that survival rates can be improved simply by changing the time and place where fish are stocked. Based on this evaluation, the department has established a set of stocking guidelines for C.J. Strike. For example, studies determined that when catchable rainbows were stocked at the Cottonwood boat ramp, anglers caught four times as many fish as when they were stocked in the Snake River Arm. Therefore, all catchable rainbow trout are now stocked at this location and allowed to disperse throughout the reservoir on their own. The study also found that when Snake River flows exceed 15,000 cubic feet per second, excessive numbers of trout are washed over the dam. Knowing this, Fish and Game now delays hatchery trout releases until river flows drop below this level. Using these stocking criteria, the department has stocked about 25,000 catchable and 200,000 fingerling rainbow trout into C.J. Strike Reservoir annually. If surplus fish are available, these numbers can fluctuate. For instance, during the early 1990s six times as many catchables and about 2 1/2 times more fingerlings were stocked annually. These fish eventually created what anglers refer to as C.J. Strike's "glory days" during the mid-1990s. Since then, stocking levels have returned to normal levels, yet catch rates remain great. And the future looks even brighter. As part of the C.J. Strike Dam relicensing agreement, Idaho Power Company-as a term of mitigation-will take over stocking catchable-sized rainbow trout in the reservoir. Idaho Power will stock about 65,000 catchables annually, or about 2 1/2 times more than have been stocked by Fish and Game in the past. The department will continue to stock about 200,000 fingerling trout annually. This will be great for rainbow trout anglers in southern Idaho. Not only will stocking levels in C.J. Strike increase, but by banking the 25,000 catchables and 200,000 fingerlings that Fish and Game formerly stocked, the department can stock more trout into other Idaho waters or increase stocking rates in C.J. Strike. So, what are you waiting for? Get a license, rig up a rod, head for C.J. Strike Reservoir, and give its fast growing and plentiful rainbow trout a try.