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NUMBER 1, 1977 1 The Humpback Chub, Gila cypha, in the Grand Canyon Area of the Colorado River 1 ROYAL D. SUTTKUS Tulane University, Museum of Natural History Belle Chasse, Louisiana 70037 GLENN H. CLEMMER Mississippi State University Mississippi State, Mississippi 39762 Perhaps the earliest recorded observation of the hump- back chub in the Grand Canyon is that of the Kolb brothers (1914). Referring to a May trip (exact date not given), they heard a peculiar noise soon after lo- cating their camp at the mouth of the Little Colorado River. The following are quotations from their writing, "Then Emery discovered what it was. On the opposite side of the pool the fins and tails of numerous fish could be seen above the water. The striking of their tails had caused the noise we had heard. The "bony tail" were spawning. We had hooks and lines in our packs, and caught all we cared to use that evening". "They are otherwise known as Gila Elegans, or Gila Trout, but "bony tail" describes them very well. The Colorado is full of them; so are many other muddy streams of the Southwest. They seldom exceed 16 inches in length, and are silvery white in color. With a small flat head some- what like a pike, the body swells behind it to a large hump." The latter statement leads us to believe that they had what is now known as the humpback chub, Gila cypha, rather than what is presently known as the bony tail, Gila elegans. Although the holotype of the humpback chub, Gila cypha, was taken from the Colorado River near the mouth of Bright Angel Creek sometime prior to the fall of 1942 (Miller, 1946) very few specimens have been taken during the subsequent years. As recently as 1973, Minckley made the following statement, "Almost nothing is known of the biology of this [Gila cypha] fish, prin- cipally because of the difficulties in collecting in its pre- sumed habitat, and its resulting rarity in collections". We began our study of the fishes of the Grand Canyon area in 1970 and made 15 float trips by September 1976. In the course of our studies we discovered a Gila cypha population and have accumulated a significant amount of biological information which is presented herein. Methods and Materials Methods of counting fin rays and scales and methods of measuring follow those of Hubbs and Lagler (1964) 'Contribution Number 12. Tulane University, Museum of Natural History. with the following exceptions. The width of gape was measured to the lateral side of the lips at the juncture of the upper and lower lips. The middorsal head length was measured from occiput forward to most anterior tip of snout or upper lip. The pre-pelvic length was mea- sured from insertion of left pelvic fin to most anterior tip of snout or upper lip. The tip of chin to isthmus measurement was made from the anteriormost tip of the chin posteriorly to the posterior margin of the rugose area at the "V" of the isthmus. The tip of snout to isthmus measurement was made to the same posterior point as the foregoing measurement. All measurements were made with a dial calipers to the neareSt 0.1 mm. Our earlier collections from the Grand Canyon area contained only young and juvenile Gila. In June of 1976 we were fortunate to obtain four adults from the mouth of the Little Colorado River (Suttkus and Clem- mer, in press). Two adults, salvage specimens, were ob- tained from Powell Reservoir. In addition we examined specimens taken in 1967 from below Glen Canyon dam and from Powell Reservoir. These latter two series of specimens were formerly housed at Utah State Univer- sity and recently have been transferred to the U.S. Na- tional Fish and Wildlife Laboratory at Ft. Collins, Colo- rado. Also we obtained four specimens on loan from the Museum of Northern Arizona. Accurate measurements were difficult or impossible on these latter three series because of improper methods of preservation; thus some dispersion of data on scattergrams is not true variability but a reflection of inability to make accurate measure- ments. Most specimens were distorted and twisted. Pre- sumably Holden and Stalnaker in the removal of gill arches from some specimens, removed and discarded both left and right opercular elements so head length and post-orbital measurements were not possible on these specimens. Some fins (particularly the caudal) were dam- aged or broken off, so no measurements could be taken. We did not estimate the measurement when the tip of the fin was missing. Abbreviations for repositories of examined material are: TU - Tulane University, Museum of Natural His- tory, NFWL - National Fish and Wildlife Laboratory at Ft. Collins, Colorado, and MNA - Museum of Northern Arizona.