Bill asked so here is the 98-cent story -
In the late 1960’s, the Department of Fish and Game maintained a Field Station, originally on Jed Smith Drive near the Sacramento State University, and later moved to Nimbus in the early 1980’s to share a larger new office with the Region 2 staff. At that time, Robert R. Rawstron, an Associate Fisheries Biologist at the time, was working on developing a trophy trout fishery at several large northern California “two-story” reservoirs.
The initial study waters were Isabella, Pine Flat, and Berryessa. The concept was to release hatchery produced rainbow trout in the spring at a size large enough to prey upon the abundant threadfin shad population. 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 juvenile trout and bass. The basic concept was the trout would feed on the shad, grow to a larger size and be largely unavailable to anglers in the summer.
Rawstron’s study proposal suggested hatchery produced catchable-sized trout be stock a size of at least 8 inches (one year in the hatchery) in the springtime and 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 was 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. Due to the success of the program at the study waters, stocking strategy was expanded to several other northern California reservoirs.
One of the original goals of the program was to produce trout of at least five pounds, however, the program failed to ever reach that goal. Additionally, Fish and Game Commission policy required a minimum of 50% of the stocked trout be harvested, but return by number released never reached 50%. As an alternative, Rawstron rationalized the program reached the goal by returning 50% by weight, since the trout usually reached a size of 16 to 24 inches after one or two years in the reservoir.
Unfortunately, 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. The fishery was most successful in the fall as water temperatures dropped from the summer highs to around 64o 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 64o F., and the fall spawning as temperatures dropped was usually not successful due to decreased availability of plankton for the juvenile fish. The surface feeding trout were readily available to anglers fly fishing small one inch long thread fin shad patterns, although spin anglers did even better fishing a small silver cast master lure.
Several factors led to the demise of the “Trophy Trout Program” including the development and popularization of downriggers and fish finders that 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 inland 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.
Many fly anglers remember the great and exciting fall fishery developed by Robert R. Rawstron and the Department’s early Coldwater Fishery Studies. The details of the studies can be found in a couple of technical articles published in California Fish and Game and authored by Rawstron. One of my first jobs as a fishery biologist was coordinating the tagging and record keeping for the Lake Berryessa studies in the early 1970’s while assigned to the Region 3 office in Yountville. Interestingly, my familiarity with the trophy trout program as a fly angler was one of the winning commentaries I used during an interview to help me get my first fishery biologist job. The new job was in fact a promotion from my existing position as a Fish and Wildlife Assistant at the Nimbus Fish Hatchery.