OCR Text |
Show and III waters are reduced to 6.8 percent and 1.2 percent, respectively. At the present time it is not possible to determine what the new State classification for fishery quality would be. An evaluation of Unit conditions by State biologists would be required to reclassify the stream sections. In those sections of stream below Unit features where flows would periodically be reduced below the recommended levels, fish would not be expected to survive. However, it would be expected that aquatic invertebrate and algal populations would continue to exist. In stream sections where upstream recommended minimum flows would be prodaced by seepages and tributary inflow it would be expected that fish populations would survive and maintain themselves but that the reductions in water velocity and depth would create adverse conditions that would reduce the size of fish populations. Substantial reduction of velocity during summer months would tend to create conditions more favorable to so- called " trash" fish than trout. Too low a winter flow would increase the hazard of formation of dastructive anchor ice. The Bureau of Reclamation recognizes that at present there is inadequate knowledge relating the effects of lower flows upon stream biota. Studies to obtain additional data are being formulated. Fish ( 1) Rare and Endangered Species Collection records for the Bonneville Unit area indicate the presence of Colorado cutthroat trout, a hybrid of the Utah cutthroat trout, the introduced Yellowstone cutthroat trout, the June sucker, and the least chub."^> °° Of these species only the least chub is classified as rare. J' / M" The status of the other species is still undetermined. However, it is generally concluded that the Yellowstone cutthroat and rainbow trout have largely replaced native stocks of Colorado and Utah cutthroat in streams through hybridization following widespread 348 |