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. REFERENCE NUMBER: CITATION: 006 Hamman. R.1.. 1981a. Spawning and culture of Colorado squawfisb in raceways. Progressive Fisb-Culturist. 43(4):173-177. SPECIES AND LIFE STAGE: CS, CS_ADU, CS_EGG, CS_LAR TOPICS: ute History, Production, Culture Techniques, Temp, Diet, Water Quality COLORADO SQUA WFISH, BROODSTOCK, ARTIFICIAL SPAWNING, NATURAL SPAWNING, SUBSTRATE, FECUNDITY, PH, DISSOLVED OXYGEN, AMMONIA, OVERCROWDING, TEMPERATURE FLUCIUATION KEYWORDS: . SUMMARY: Brood stock consisting of 13 wild adults from the Colorado River between Grand Junction, Colorado and Moab, Utah and 14 wild adults from tbe Green River between Ouray and Jensen, Utah and two groups of hatchery reared fish were spawned at Dexter National FISb Hatchery by several different techniques. One group of wild fish were allowed to spawn naturally in a concrete raceway over substrate of boulders (30 - 40 em) and cobble (4 - 10 em) water depth ranged from 10 - 76 em. Five wild females were injected with acetone-dried carp pituitary (40 mg) in a solution of oxytetracycline hydrochloride (10 ml) and allowed to spawn un-aided in a raceway with similar substrate. Thirty-nine hatchery reared females were injected at 4 mg/kg body weight and 39 were injected at 8 mg/kg body weight. When eggs could be expressed these fish were anesthetized and were stripped into plastic pans. Water diluted milt from four males was added to these eggs which were then stirred for 45 min and water bardened for 50 miD. Eggs were poured onto 53 x 53 em trays covered with 1.4 mm mesh hardware cloth and angled 300 to an 811min flow and incubated at 20-210C or 12-130C. Males began acquiring small tubercles on head, operculars and fins in late April at 150C and had fully developed milt by June at 2ooC. Females showed no spawning characteristics until June. Fecundity and survival of fry varied greatly among the treatments. Wild uninjected females averaged 25,000 eggs from which 7,500 fry were hatched. Hatching began at 96 hand took place over 48 h. Larvae were 6.5 - 7.0 mm TL. Fecundity of injected wild stock averaged 55,000 eggs from which 32,500 hatched naturally and 4,500 of 5,000 eggs incubated as described above were hatched. Hatching began in the raceway at 90 h (22 - 240C) and was complete 40 h later, hatching in trays began at 90 h and was complete 30 h later (20 - 210C). All larvae ranged from 6.5 - 7.5 mm TL. Hatchery females owlated about 24 h after one injection and produced 78,540 eggs or 10,542 eggs per kilogram of body weight. Survival however was low, 2,000 eggs (3%) hatched. Eggs incubated at 20 - 210C began hatching at 96 h and were complete 25 h later, eggs incubated at 12 - 130C began hatching at 145 b and were complete 35 b later. No difference in egg fenility or fry survival was noted between the two water temperatures. Fry were reared in previously fenilized recirculating systems held at 23 _ 240C. Oa:asional temperature drops of 10000ver 10 min were tolerated by the fish. Also an oxygen depletion from 9.9 mgIL down to 1.5 mgIL occurred causing only 60 monalities. . Injection of wild fish and subsequent spawning over natural substrate in a raceway was superior in egg production and hatching success. Uninjected wild females had 30% hatching success, injected wild females had 67% success and anificially' spawned hatchery females had 3% hatching success. FISh were able to endure variable culture conditions including low dissolved oxygen (1.5 mgIL), high ammonia nitrogen (2.0 mgIL), high carbon dioxide (15.0 mgIL), high pH (9.0). A-6