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Colorado River from the right and the rest enter the river from the left. The variation in color patterns was not restricted to tributary samples from either side of the river. Reproduction occurs during late spring, summer and early fall. Direct spawning observations were made on two occasions. A ripe female collected on April 28, 1975 voided numerous large eggs upon slight pressure. This female was taken from Crys- tal Creek (River Mile 98.2). The water tempera- ture of the creek was 220C at the time of collec- tion. During the same time the Colorado River was 11oC. Nuptial coloration was apparent; the corner of mouth, the upper portion of operculum, bases of pectoral, pelvic and anal fins and lower portion of caudal fin were reddish. A ripe male was taken from Clear Creek (River Mile 84.2) on June 6, 1975. The water temperature was 200C at the place of capture. Besides being tuberculate the male specimen had the same reddish areas as described for the female mentioned above but per- haps even brighter. Tuberculate males were taken during last of April through summer months as late as the middle of November. The November collected specimens were in postspawning condition and ex- hibited blunt pointed tubercles which were believed to be in a state of regression. A sample of young taken from Boucher Creek (River Mile 96.5) on June 4, 1976 represented an early spawning. The six specimens ranged from 7.3 to 12.7 millimeters in standard length and aver- aged 10.3 mm in standard length. Another sample which represented a late spawning was collected from the paria River (River Mile 0) on November 16, 1975. The thirty-four specimens ranged from 12.4 to 20.3 mm standard length with an average of 15.6 mm. For comparison, an adult speckled dace may exceed a hundred millimeters in standard length. The original description of the humpback chub, Gila cypha, was based on specimens from the Grand Canyon area (Miller 1946a). We collected one adult humpback chub from Shinumo Creek on August 1, 1975. This individual was photographed and re- leased. Four adult humpback chubs* were obtained from the Little Colorado River near its mouth on June 2, 1976. No adult specimen of the bony tail, Gila elegans, was taken during the survey. Posi- tive identification of young and small juvenile specimens of Gila has not been made up to this time but we believe that these small specimens are Gila cypha. During our study young or small juve- nile Gila were taken at River Mile 44, 61.5, 65.8, 69, 71 and 108.7. A single young specimen (35.6 rom in standard length) was taken at the River Mile 44 site on September 8, 1970. Additional attempts to collect Gila above the Little Colorado River (River Mile 61.5) failed to produce any more speci- mens. Although Holden and Stalnaker (1970) re- ported specimens of Gila from Lee's Ferry our numerous attempts with a small-mesh seine revealed no Gila of any size. In addition to the adult Gila that was captured and released at the Shinumo Creek site, two young Gila were taken on September 23, 1975. One meas- ured 32.3 mm and the other 32.8 mm in standard length. The four smallest specimens of Gila ob- tained from the mouth of the Little Colorado River were 26.0, 27.3, 27.6 and 28.2 mm in standard length. These specimens were collected on July 30, 1975. The smallest specimen taken at River Mile 69 was 27.6 mm in standard length and was collected on September 22, 1975. Two small specimens of Gila were obtained from the Colorado River at River Mile 71 on April 26, 1975. These two *Gila cypha were collected under F~deral Permit No. PRT 8-l85-C. specimens measure 26.2 mm and 28.1 mm in standard length. The three smallest specimens taken during the study were obtained from the same area (River Mile 71) on September 22, 1975. These three speci- mens measure 24.5, 24.6 and 24.6 mm in standard length. These data are important additions to our knowledge of the chub in the Grand Canyon area and will be useful in the planning of continued stud- ies. Unfortunately we have not observed spawning activity nor have we observed any ripe individuals. In consideration of the size of the young and the various dates of collection we believe that spawn- ing may occur at various times during the summer months. However, the present spawning pattern may be a disrupted one which has resulted from the imposed environmental conditions. We believe that the impoundment of the Colorado River by the Glen Canyon dam and the subsequent continuous unnatural releases of cold bottom water has had a devastating effect on the Gila popula- tion. We believe our samples are evidence that the distribution of Gila in the Grand Canyon area has been reduced to an area near and extending a few miles below the mouth of the Little Colorado. Further, we believe the continuance of the Little Colorado River in its present physical" and chemi- cal state is essential to the survival of Gila in the Grand Canyon. The Little Colorado River and the main Colorado River downstream to Shinumo Creek is critical habitat. Our survey did not disclose any specimens of the Colorado squawfish, Ptychocheilus lucius. Numer- ous sampling sites should have produced young or juveniles if the species still exists and repro- duces in the Grand Canyon area. We are convinced that the Colorado squawfish was extirpated from the Canyon area by impoundment and the conditions that prevailed thereafter. The fifteen exotic species taken during the study are listed with annotations. The thread fin shad, Dorosoma petenense, an ex- otic form presumably was introduced as a forage species for the large introduced game species. The threadfin shad was collected at Spencer Creek (Mile 246), at Emory Falls (Mile 274.3) and at Scorpion Island (Mile 279.5). A single specimen of the coho salmon, Oncorhyn- chus kisutch, was seined at River Mile 194.5 on August 16, 1971. The introduced rainbow trout, Salmo gairdneri, and various hybrid combinations were taken from many of the tributaries and various places along the main river. No young or juveniles were col- lected around the mouth of the paria River and we suspect that little if any spawning is successful in that part of the river. The carp, cyprinus carpio, was as widely dis- tributed in the Grand Canyon area as the rainbow trout. Schools of individuals were observed in the main river from Lee's Ferry down to and along the shores of the Mead Reservoir and at the mouths of all moderate to large size tributaries. For example, a group of 21 was observed at River Mile 34 on July 29, 1975 and twelve were collected from the mouth of Kan?b Creek on June 9, 1975. The uppermost site for young or juvenile carp was the Little Colorado River (Mile 61.5). Young or juveniles were collected at Cardenas Creek area (Mile 71), River Mile 194.5 and at Emory Falls in the Mead Reservoir (Mile 274.3). All other collections and sightings were of adults thus indicating that the conditions prevailing in the upper stretches of the Colorado River around Lee's Ferry are not favorable spawning area even for the tolerant carp. 603