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THREATENED & ENDANGERED FISHES Table 3."Summary statistics for Apache trout rearing program, 1964-81; Percent Percenttolal No. of A nrage, Pick pick Stocked and/or stocked and/or Ynr females Eggs eggs/female off off retained retained 1964 5 370 >2 130 36.1 99 27.5 1965 17 J,853 109 1,120 60.2 742 39.8 1966 60 11,034 183.9 8,897 83.7 1967 104 25,615 246.3 20,979 81.8 4,645 18.12 . 1968:f~ 229 45,342 198 35.873 79.0 5,674 12.5 1969 .,' ,~" )75 I 75,513 431.5 52,673 69.0 16,162 21.39 1970 ;'d 146,491 106,040 72.0 18,250 12.45 1971 136,616 97,390 71.28 19,113 13.99 1972.1 ":',' 84,100 45,592 54.0 14,255 16.95 1973,,; ,',,: '" 93,264 72,895 78.0 7,986 8.56 1974 " NO RECORDS-FISH STOLEN 1975,}\ ~ NEW FISH ~ ", 1976, NO SPAWN 19171 5,616 3,531 62.9 1,042 18.55 1978 6,692 2,908 43.0 1,329 19.85 ' 1979,r,! 1980 5,616 3,531 62.87 100 1981" 149,190 96,973 65.0 2,999 \ ~, '4? I '>. f ords between 1964 and 1981 indicated that mean number of eggs produced by 2- through 5-year- old females was about 274. An average of 69.7% of eggs do not survive to hatch (Table 3). Of eggs that do hatch, an average of only 38.7% survive to be used for management purposes or brood stock. Total numbers of fish produced over the past 18 years have averaged 11.8% of the yearly total egg-take (Table 3). After eggs hatch, sac fry are difficult to train to feed, being reluctantlo accept artificial diets. Success was achieved by starting fry on powdered eggs, then switching to a commercial feed mixed with ground beef liver. Apache trout fry and fingerlings neither exhibit schooling behavior nor form into aggregates like domesticated trout. Young of this species are highly territorial and defend their territories vig- orously. This behavior is not conducive to intensive hatchery cultivation, where high numbers of fish must be raised in a confined area. The result is high fry mortality and survival only of the more aggressive and dominant individuals. At water temperatures of 50.90F, once the fry are on feed, they grow slowly, averaging 2 inches in total length after 150 days. Potential inbreeding is high because the initial brood stock was har- vested from a single population in a small head- water stream. Further, Sterling Springs Hatchery is a small production facility primarily utilized for rearing non-native salmonids for management purposes; only two raceways are allocated for Apache trout culture. This situation makes it difficult to keep the various year-classes of brood stock separate or to hold many brood stock.,The lack of space and of annual gamete production increases the probability of back-crosses of brotherl sister, mother/son, and father/<:Iaughter. Program Assessment Limited success of the Apache trout culture program is attributed to several factors working singularly or in combination. First, during 18 years, we have not learned how to culture the fish; second, the fish is "wild" and may not be suscep- tible to intensive culturing. Problems associated with culturing Apache trout can be"grouPfd into three categories: physiological, beha~ioral, and propagation methods. Low fecundity rates and slow growth rates may be physiological adaptations for survival in small, harsh, headwater streams. Further, reluctance of fry to accept an artificial. , diet, coupled with their territorial defenstf, may be a behavioral response associated with a highly competitive and limited natural system. Poor egg survival may be related to ~pawning and egg handling methods that work well on domesticated non-native salmonid strains but not with Apache trout. Hybridization with introduced rainbow trout stock has been suggested as the reason for the decline of Apache trout (Miller 1972, Behnke