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c: G ,-) ( ~ (.Q San Juan Seven Year Research Plan WORK STATEMENT/PROTOCOL .' NAVAJO DAM TAILWATER FISHERIES STUDIES - NMGF TROUT POPULATION STUDIES ( Background: With the construction of Navajo Dam, the San Juan River from the outflow of Navajo Dam downstream to the U.S. Highway 64 bridge crossing at Blanco, New Mexico has been changed from a relatively warm, silt-laden stream inhabited mostly by native fishes to a cold, cobble-bottomed stream capable of supporting salmonids. Since the early 1960's, this portion of the San Juan has been managed as a trout water by the New Mexico Department of Game and Fish. The fishery is maintained mainly by stocking; however, Bome natural reproduction is evident. Much of the angling activity occurs above the confluence of the San Juan River and Gobernador Arroyo. Below this reach, trout habitat is often limited because of the accumulation of large amounts of sediment that enter the river from Governadcr, Pump, and Horse Canyon arroyos ~ During years of high releases, these areas are flushed of silt enabling them to support healthy populations of trout and thus increase the area used by anglers. In the 3.75 mile section immediately below the dam, special bag and angling restrictions have been imposed. Coupled with the exceptionally good conditions for trout, restrictive regulations have helped to build this into one of the most popular angling waters in the western United States. Pressure count data estimates reveal that over 50,000 angler days a year are spent by anglers fishing the tailwater. Approximately 75 percent of these days are spent on these 3.75 miles of "Special Trout Water." Maintaining the quality of this valuable fishery is important both to the angler and the local economy. Because of this, studies are proposed which will examine the effects of experimental flows for Colorado squawfish on the trout fishery. Some data are available on this fiShery as the result of annual monitoring of the trout population in the Special Trout Water section of the river. These data, however, are insufficient. 'to accurately quantify true response of the trout population to different water release schedules from Navajo Reservoir. Objectives Document the seasonal longitudinal distribution of salmonids in response to the various to different flow regimes Determine the seasonal abundance of salmonid populations, and differential response of each salmonid species to various flow regimes. Changes in growth, condition, and survival of each species will be examined. Determine if fish movements occur, especially during high flows, to help evaluate habitat needs associated with these flows. Methods: Methods proposed are tentative and may change after review of other tailwater studies. Two sampling efforts are proposed for 1992. The.first will be just prior to the experimental releases in the spring and the second during the stable summer flows after the high-water release. Sampling will be done primarily by electrofishing. Data collection and analysis will be done by river mile beginning at the dam and continuing downstream to the bridge. For each river mile, all fish collected (including any native or non-salmonid species) will be identified, weighed, measured, marked for mark-and-recapture population estimation, and released. Scale samples will be taken from a representative sub- sample to estimate growth rates. The first 1,000 fish captured will be pit- l. A20