california’s trophy trout program provided great fishing opportunities

Estimated reading time: 6 minutes

Background

California’s Trophy Trout Program was started in the late 1960’s. At that time, the Department of Fish and Game maintained a Field Station. It was originally located on Jed Smith Drive near the Sacramento State University. The Field Station later relocated near Nimbus Fish Hatchery in the early 1980’s. Personnel assigned to the Field Station were often involved in developing new strategies to maintain and enhance California fisheries. Robert R. Rawstron was an Associate Fisheries Biologist at the Field Station. He worked on enhancing sport fishing at northern California “two-story” reservoirs as part of a Coldwater Fisheries Study. 

Two story reservoirs are somewhat unique to western states. The name comes from the fact that these reservoirs “stratify” in the summer. They maintain a warm surface (epilimnion), but maintain a cooler lower stratum (hypolimnion) below the thermocline. As such, these reservoirs are able to support both warmwater and coldwater fisheries. In California reservoirs, the warmwater fishery is typically comprise of a naturally producing black bass and sunfish populations. The coldwater fishery is supported annual stocking of trout and sometimes salmon. The trout and salmon are not expected to reproduce. If not caught by anglers, they will eventually die of natural causes.  

Study Goals

The California Trophy Trout Program was initated in the early 1970’s. One of the original goals identified by Rawstron was to produce trout of at least five pounds. However, the program failed to reach that goal. Additionally, Fish and Game Commission policy required a minimum of 50% of the stocked trout be harvested. The return by number of trout released during the study never reached 50%. As an alternative, Rawstron rationalized the program reached the goal by returning 50% by weight. The trout usually reached a size of 16 to 24 inches after one or two years in the reservoir. The alternative was accepted by the Commission.

Study Design

The initial California Trophy Trout Program study design included stocking hatchery produced catchable-sized trout after one year of rearing in the hatchery and at a size of at least 8 inches. The trout would be stocked in the springtime before reservoir surface waters warmed. The trout were to be stocked at a density of about 4 fish per surface acre. Several strains of rainbow trout were tested and a minimum of 200 fish of each strain were tagged and released with an external tag bearing a reward for return of the tag.

During most study years, the Kamloops strain, originally imported to California by Federal personnel at the Coleman National Fish Hatchery, was considered the most successful based on survival and growth. Other California strains, i.e. Whitney, Hot Creek, Shasta were included in the studies but did not typically perform as well. Coho salmon were also included in the study. However due to the high cost to produce fish for stocking were not included on a large scale. 

Study Waters

The initial study reservoirs were Lake Isabella, Pine Flat, and Berryessa. The program concept was to release hatchery produced rainbow trout in the spring at a size large enough to prey upon abundant threadfin shad populations. Threadfin shad were imported to several southern California reservoirs in the 1950’s and later transferred to northern California reservoirs. They were also considered to be a food competitor with small trout and juvenile bass. The concept was the trout would feed on the shad and grow to a larger size. They would not be available to anglers until the fall and winter when lake surface waters cooled.

Success

Eventually due to the success of the program at the study waters, a similar stocking strategy was expanded to several other northern California reservoirs. The fishery was most successful in the fall as water temperatures dropped from the summer highs to around 64^o F. At that time, the thread fin shad would return to the surface in schools in a second fall spawning. Thread fin shad typically spawn in the spring as water temperatures rise to 64^o F., and again in the fall spawning as temperatures dropped. The fall spawning was usually not successful due to decreased availability of plankton for the juvenile shad. 

The trout chasing and busting schools of shad at the surface were readily available to fly anglers. Several new fly patterns were developed in the early 1970’s to take advantage of the fishery. One of the most popular was created by innovative angler and fly tyer Hal Janssen. The fly is tied with Mylar tubing over a flat thin lightweight core with painted with eyes. Janssen’s threadfin shad pattern was easy to cast on with a fly rod and when striped back darted like a real shad. The reflective property of the Mylar effectively imitated the shiny sides of Threadfin shad and made it a very successful pattern. Occasionally a few trout would chase schools of springtime surface spawning threadfin shad but the fall fishery was the most consistent. 

Problems

Several factors led to the demise of the “Trophy Trout Program”. First, most likely due to hatchery domestication, very few tagged trout were ever caught after two years in the reservoir. It was suggested after reaching maturity, most of the fish perished and most reservoirs lacked suitable spawning tributaries and rearing habitat. Secondly, the development and popularization of downriggers and fish finders allowed anglers to target and harvest the trout during the summer period, leaving fewer fish for the fall surface fishery. In addition, there has been a declining emphasis during the past 25 years on “experimental management and research” for sport fisheries by the Department. Hatchery produced trout strains such as the Kamloops strain have become more domesticated in the ensuring years and their ability to survive in the wild reduced.

Additionally, if the reservoir was full and spilling water in the spring after the trout were stocked, many of the trout migrated out of the reservoir into downstream waters. The was especially prevalent at Lake Berryessa and Pine Flat Reservoir. Fortunately for fly anglers, the spill over trout created excellent fly fisheries in Putah Creek and the Kings River. Unfortunately, the development of small-scale hydro development at most low elevation dams resulted in few if any lake water spills.

Remembering

Many fly anglers remember the exciting fall fishery developed by Robert R. Rawstron and the Department’s early Coldwater Fishery Studies. The details and results of the studies can be found in a couple of technical articles published in California Fish and Game and authored by Rawstron. Many California fly anglers remember the exciting times chasing and casting to surface feeding trout from float tubes or small prams. In addition, one of my first jobs as a Fishery Biologist was coordinating the tagging and record keeping for the Lake Berryessa studies. Interestingly, my familiarity and experience fly fishing Lake Berryessa was instrumental in obtaining the position. The new position was in fact a promotion from my existing job as a Fish and Wildlife Assistant at the Nimbus Fish Hatchery.

For more information about Dennis P. Lee and his career see the Home page. The Contact Page refers to articles he has submitted to California Fly Fisher for more reading.