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52 formation of a small overflow pond of shallow water covering an area about 350 square meters, and a mean depth of 30 cm. In April 1977, 300 adult pupfish (in a 172 ?: 128 a), collected from the Warm Spring refuge, were introduced into this habitat. Sixty- three days later fry were observed in the overflow area on the west side of the pond. Eighty-four days after introduction, young pupfish were easily observed and trapped throughout the shallow pond; however, they were never observed or trapped in the main channel (-'depth 2.51. The adults which were introduced into the main channel were rarely seen. The incipient population appeared to have been readily reestablished. Therefore, the remaining objectives of this study were pursued. The estimation of 1977, June, 1978, and and recapture method. weighed to the nearest nearest mm, caudal fin population size n was made during September, ieptember, 1978, using the Peterson mark Pupfish were captured in minnow traps, 0.1 gram, standard length measured to the clipped, and then released. Population size was estimated at 2,000 fish in September, 1977, 9,000 fish in June, 1978, and ti 10,000 fish in September, 1978. It appeared that the population had stabilized during the 1978 season. This may be due to two reasons: the population stabilizing near the carrying capacity of the pond or, emigration of young fish downstream from the pond (and out of the sanctuary) may be cropping the population below the carrying capacity. The second thesis is supported from observations made in late June, 1978, when I estimated a population size of 560 fish in an area 25 meters downstream from the pond (below the downstream dam). then explored the marshy areas and other ponds one mile downstream from the sanctuary where I found pupfish (< 25 mm) young quite common. The general distribution pattern is described as a population of segregated age groups -- with larger fish (older) dispersing just a short distance from the sanctuary and the smaller fish (younger) dispersing further downstream. The average size in September, 1977, of the first generation was 28.3 mm, with a mean weight of 0.9 grams (n=389)• In September, 1978, the average size of the total population was 30.4 mm, with a mean weight of 0.98 g (n=821). In September, 1978, less than ten percent of the population was made up of adult pupfish, which had a mean length of 42.9 mm and a mean weight of 2.7 g. I classified these fish as Age Group I, they are the surviving members from the 1977 first generation. Age Group II was made up of 1978 young and had an average length of 29.3 mm and a.;& weight of 0.84 g. By calculation, I estimated the standing crop and production at various time intervals. Biomass in April, 1977 (0.81 kg), was due entirely to the introduced adults from Warm Spring