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In following humpback chub on a daily basis, it was noted that they do exhibit movement to a selective depth and microhabitat. Fish were most often observed, by radio tracking, in midmorning and midafternoon near shore in water 3-5 m deep, and further out toward midchannel at midnight and midday. Some exchange of individual fish between isolated populations was documented. One tagged fish moved from the point of tagging in Westwater Canyon upstream 14.4 mi to the Black Rocks area. This movement was observed over a span of 232 days. Movement of chubs in the Little Colorado River was generally greater than in the,Upper Colorado River. Fish captured from 3 1/2 weeks to 13 months after tagging moved 0-1.7 mi, averaging 0.4 mi. in 1980. Some additional information supports the hypothesis that small fish, YOY and juvenile, moved downstream out of the Little Colorado River. Movement of fish in the Little Colorado will be further analyzed in the report on this work to BR in March 1982. Captures of young humpback chub within the Black Rocks area supported the conclusion that all life stages of the chub occur within the same limited area of river and that the fry did not drift downstream to any significant degree. Limiting Factors J{~~ • D~ Temperature - Valdes~(~-9S.~j observed ripe male and gravid female humpback chub at Black Rocks at a water temperature of about 12°C. Some of these fish were hand spawned at the site of capture with the aid of carp pituitary injections on June 2, 1980. Three weeks later most females taken there were spent, indicating spawning had been completed ( The tempperature had risen to above 18°C by this time. Valdes also observed gravid females on May 15 at 12-14°C and spent females on June 1 at about 16°C at Black Rocks in 1981. Kaeding (personal communication) was able to express eggs from a female humpback chub taken in the Little Colorado River on April 1, 1981. The water temperature there ranged from 18 to 20.5°C at that time. By May 15 most females caught were spent, indicating spawning was about finished. Natural spawning of captive Little Colorado humpback chub in a con- trolled hatchery environment occured at Willow-Beach NFH at a tempera- ture of about 18°C on May 5, 1981 ( }. ~ A~~y~ Humpback egg and ~1,,,ar~a1 development and survival are dependent on temperature. Hamman,pll~;Efound that only 12X of a group of eggs in- L' cubated at a temperature of 12-13°C hatched and only 2X of them survived to become feeding larvae. At 16-17°C hatching success increased to b2X and 56X of the eggs produced feeding larvae. At 19-20°C the percent hatch rose to 79-84X and 79-80X resulted in feeding larvae. Hatching at i9-22°C occured 4 to 7 days after fertilization while at I6~~t~~ook 7 to li'days and at 12-13°C, 14 to 20 days. Bulkley et al re- G- ported from 90 to 100X hatching success for humpback eggs at 26°C as opposed to a SOX hatch at 14°C. Clearly, temperatures less than 16°C are detrimental to humpback egg and larval development and survival.