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<br />. <br /> <br />. <br /> <br />0418 <br /> <br />Lake trout normally spawn in about 20 feet of water from mid-October to <br />mid-November. Under existing thermal and biological conditions at Twin <br />Lakes Reservoir, the fry hatch in about 128 days or during the middle or <br />latter part of February. About 30 more days are required for the absorp- <br />tion of the yolk sac in order for-the fry to free themselves from the <br />spawning gravel. Successful lake trout spawning in Twin Lakes Reservoir <br />at present is due principally to the constancy of the water level during <br />this critical October to April period. <br /> <br />The fishery of Twin Lakes Reservoir will be protectedo To protect fish <br />spawn, water level fluctuation should be kept to a minimum during the <br />period from October 15 through Harch 1. If the evacuation of water from <br />Twin Lakes should exceed 15 feet during the period from October 1 through <br />April 30 the spawning success of Mackinaw Trout will be impaired. <br />. <br /> <br />Although a successful spawn is not necessary each year, this criterion <br />should be met during three years out of any five-year periodo Operation <br />studies indicate that the water level will usually fluctuate within these <br />limits during the critical spawning period. The Bureau of Reclamation <br />in cooperation with the Bureau of Sport Fisheries and Wildlife and the <br />Colorado Division of Game, Fish and Parks plans to monitor the marine <br />biology before construction begins and initiate a limnology study <br />(biOlogical, chemical, g90graphical and physical features) of T,.in Lakes <br />beginning early this spring and continue through construction and the <br />first years of operation to develop management and operational criteria <br />to protect and enhance the fishery as recommended in the Bureau of Sport <br />Fisheries and Wildlife's August 28, 1969 report. <br /> <br />2. Physical.--Although the natural reproduction of these lake <br />trout will probably not be impaired, we know that some fish will be lost <br />thrcugh the pump-back phase of operation. The Bureau of Sport Fisheries and <br />Wildlife was not able to predict the number of fish that mi~lt be lost in <br />the unscreened unit; therefore, it did not recommend screening, estimated <br />to cost $700,000 or more, to avoid fish losses. Project funds will be made <br />available to the Bureau of Sport Fisheries and Wildlife to fund fish loss <br />studies which ~e to be conducted by the Colorado Division of Game, Fish <br />and Parks. If significant gamefish losses do occur from powerplant opera- <br />tion, including the pump-back phase, recommended measures designed to <br />alleviate fish loss will then be employed. <br /> <br />The effects of Twin Lakes enlargem9nt and the operational impact associat9d <br />therewith will be covered in a separate environmental impact statement. <br /> <br />3. Fish and Wildlife, and Recreation,--We do not anticipate an <br />adver'se impact on fishing, \.,ildlife and recreation use from the pumped- <br />storage powerplant. <br /> <br />5 <br />