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.' . REPORT ON ELECTROSHOCKING SURVEY OF THE LOWER GUNNISON RIVER FROM THE NORTH FORK CONFLU~NC~ DOWN TO THE AUSTIN BRIDGE, SEPT. 4TH AND 9TH, 1981. The attached table is a summary of the numerical density of the fish species collected on 9.3 miles of the Gunnison River, from the North Fork confluence to the Austin Bridqe. The collec- tion was divided by section, range, and township as designated on the U. S. G. S. maps, Lazear and Orchard City quadrangles. The collection proceeded from upstream to downstream. Suckers and sucker hybrids comprise 65.5% of the sample (numericallY) while rainbow and brown trout comprised 21.8% of the sample. We found very little evidence of brown trout natural re- production and virtually none for rainbow trout. Thus, the Gunnison River below the North Fork confluence cannot be considered a viable wild trout fishery capable of sustaining itself without stocking. However, that is not to say that this portion of the Gunnison (North Fork confluence to the Austin Bridge) is not a good trout fishery. Twenty-six trout (rainbow and brown) collected were in excess of 30 cm total lenath, and half of those were over 16 inches or 40 cm total lenqth. in addition, the majority of the rainbow collected (195) were in the 6-10 inch size class and were in very robust con- dition. Most of the rainbow were apparentlY from a fingerling rainbow plant of 50,000 fish made at the North Fork confluence in April, 1981. Twenty-six of 50 scale samples taken on rainbow trout from 6"-10" in size just above the North Fork confluence on the main Gunnison were from the sprin~ plant as indicated by a false ann u 1 usa t 2. 5 II to 4 II b a c k - c a 1 c u 1 ate d 1 e n 9 t h . Our aae and nrowth data indicates the rainbow have been grow- in~ at the rate of almost one inch per month, probably the best growth rate for rainbows in streams anywhere in Colorado. The rain- bow and brown collected in the 1611 to '2011 ranae were also in robust condition, again attesting to the potential for excellent trout growth in this section of the Gunnison River. Our electroshockinq efficiency on rivers of this size is usually about 5% on all fish over 6" total length. We are somewhat more efficient on large suckers due to their stron9 positive electro- taxis; thus, the numerical data in the attached table is probably biased in favor of the suckers. If the numerical majority of suckers in the sample were used as a biological basis for concluding that the Gunnison River from the North Fork confluence to the Austin Bridge was not a good trout fishery, then the same would apply to the Gunnison above the North Fork confluence to the Crystal Dam. Suckers definitely form the numerical majo~ity in the Gunnison above the North Fork confluence as well. The poor snowpack in the winter of 1980/81 and subsequent seve~ely r~duced flows and elevated water temperatares in the Gunnlson Rlver below.the North Fork confluence did not preclude good growth and survlval of trout in this section of rtver~