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
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
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!