June 19, 2006

By Joe Kozfkay, Fisheries Biologist, Southwest Region

Mention the possibility of going fishing at C.J. Strike Reservoir to any of Idaho's multi-species anglers and their head may explode. Too many possibilities and often just too little time!

Should you cast small jigs in the tulies 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, let's slow down, catch our breath, and talk about just one aspect of this popular fishing destination, the rainbow trout.

C.J. Strike Dam, built in the early 1950s, impounds both the Snake and Bruneau Rivers. Although rainbow trout and native redband trout spawn in the headwaters and tributaries of these river drainages, nearly all rainbow trout found within the reservoir are produced in one of two Idaho Department of Fish and Game's trout hatcheries located in Nampa and Hagerman. Fish and Game has consistently stocked C.J. Strike since shortly after the reservoir was impounded.

C.J. Strike Reservoir offers a unique set of 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. Abundant forage such as zooplankton, midge larvae, and other aquatic insects create an ideal forage base. Stocked rainbow trout gorge themselves on this abundance and are able to grow rapidly. Rainbow trout stocked as three- to four-inch fingerlings in April will reach 14- to 15-inches by November of the same year, a growth rate that is quite remarkable compared to other systems in Idaho.

On the other hand, life isn't always so pleasant for CJ rainbows. The abundant bass, catfish, and pikeminnow don't hesitate to take advantage of the naivety of recently stocked fingerlings, and forage on them heavily, especially during the first week after stocking. Predatory fish with big enough mouths even chomp down on some of the eight to ten-inch catchable rainbows. Don't forget the fish-eating birds too. It can be a tough world for a newly planted hatchery trout. In high water years, rainbow trout may get free rides either through the turbines or over the spillway. Although the survivors create a popular winter and spring fishery in the tailwater, these fish suffer higher than average mortality rates and are permanently 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 by simply changing the location where fish are stocked and the time at which fish are stocked, survival rates can be improved and thus more fish are available for anglers.

Based on this evaluation, Fish and Game has established a set of stocking guidelines for CJ Strike. For example, studies determined that when catchable rainbows were stocked at the Cottonwood boat ramp, anglers harvested four times the number of fish compared to stocking fish 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. Additionally, the study learned 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, IDFG 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 two and a half times more fingerlings were stocked annually. These fish eventually created what anglers refer to as CJ 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 CJ Strike relicensing agreement, Idaho Power - as a term of mitigation - will take over stocking of C.J. Strike Reservoir and will be required to stock an equal number of fingerlings (200,000) and about two a half times more catchables (65,000) than have been stocked by Fish and Game in the past. 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, fisheries personnel will be able to either stock more rainbow trout into other Idaho waters or further 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!