7969 - Laserfiche WebLink

Home Browse Search

258 C. A. KARP AND H. M. TYUS [Volume 50 UTAH ; COLORADO ~- ~ ARE E,y ~~L F9 ~ u r a ~~ I 0 ~P ~ ~ (vA^~~ 1 y ` 0 P ~~ ~ _I SAP ~ VE 4S YQ A/ Pq p~nnaaar ool ~~,d un Nac~onai p~yFq CRALG ?~~~ ,la~^ a ~anY Mon umenl M AY B E L L• ~ Gmi Yampa ~anYOn p,Q P, Echa Parts ~ peerlotlge e Park M'ILLI ,„ A S Gpb~~ SCaIE Ix MILES r5 aULE IH rNILOMEiEPS FpgK Fig. 1. Yampa and Green rivers, Colorado and Utah, showing the boundaries of the study area and Dinosaur National Monument. at least twice each spring in 1987 and 1988, and Lodore Canyon (Green River) was sam- pled once each spring. Survey sampling (in- cluding trammel netting) was conducted throughout the Monument in July 1986 to locate humpback chubs. Use of trammel nets was discontinued after this effort because of trauma to the fish. Sampling trips in Yampa Canyon occurred at weekly intervals (preceding and following first and last capture of ripe fish) to insure an accurate assessment of the humpback chub spawning period. Our efforts were less inten- sive in the Green River portion of the Monu- ment because earlier sampling had yielded few adult chubs in these reaches (Holden and Crist 1981, Miller et al. 1982). Sampling pre- ceded peak flows and was suspended during highest runoff (2-4 week period depending on water year) because of sampling problems in high water. Sampling ended each summer with attainment of base flows (approximately late June to early July). Our efforts were re- stricted to the spring and early summer be- cause of boat accessibility. However, two areas in Yampa Canyon that yielded hump- back chub in the spring (Big Joe Rapid and vicinity, Warm Springs Rapid and vicinity) were sampled in September 1989 via heli- copter and by foot to assess habitat, availabil- ity, use, and substrate composition during low flows. All chubs greater than 85 mm total length (TL) were identified to species using estab- lished morphological characters (Smith et al. 1979, Douglas et al. 1989). We did not evalu- ate habitat use of young humpback chub be- cause we could not reliably distinguish young of the various Gila species. Humpback chub greater than 250 mm TL were tagged with uniquely numbered Carlin-dangler tags for recapture information (e. g. , growth and move- ment data). Sex determination was based only on expression of eggs or milt from ripe fish, either spontaneously or following manual pressure on the abdomen. Fish with breeding tubercles but without expressible sex prod- ucts were considered in reproductive condi- tion. Riffles, small rapids, runs, eddies, pools, and backwaters were sampled. Because wa- ter turbidity precluded visual contact with humpback chub, it was necessary to esti- mate the point of capture. Physical habitat parameters recorded at each humpback chub capture included water depth, temperature, and substrate type. Depth was measured with a calibrated rod, gross substrate type was described from visual and manual examina- tion, and temperatures were obtained with