7017 - Laserfiche WebLink

Home Browse Search

In addition,.a large series of bonytail chub specimens from Dexter NFH were included in the analysis. Based on these pre-judged samples, several morphological characters, including head, nuchal hump, and certain body dimensions, a posteriorly separated a-large percentage of samples in like manner, thus showing promise for field application in this population. Recommendations were made for further study of these characteristics. These preliminary results may indicate that a low percentage of hybridization is occurring between Gila spp. in this habitat as only three "intermediate" specimens were detected out of over 1200 examined. Rosenfeld, M.J. The use of chromosomes in fisheries biology: population and species discrimination in chubs (genus Gila). Unpub. ms. 9 p. Presents evidence that chromosomal states are capable of separating three species of Colorado River chubs and that G. cypha from the upper Colorado (Black Rocks) are distinguishable from Little Colorado River populations based on specimens from hatchery stocks (however cypha progeny may have been of mixed origin?? see Valdez, 1985, above). Points out the value of chromosome analysis as a potential nonlethal technique for identifying chubs for management purposes. Rosenfeld, M.J. Morphometry of fishes in the genus Gila (Cyprinidae) from the upper Colorado River basin. Unpub. MS. 26 p. Presents results of multivariate analyses performed on data from over 600 live specimens of upper basin Gila from the Colorado and Green rivers, and lower basin material from the Little Colorado and Virgin rivers and G. elegans hatchery stock derived from Lake Mohave. Chief sources of morphological variation are identified and interspecific and -subspecific differences and similarities are discussed. It is postulated that forms formerly regarded as "intergrades" (e.g., Holden and Stalnaker, 1970) mostly constituted G. cypha. Interregional variation was noted between Green River and Colorado chubs (both species?) and the aforementioned (see Moretti et al., above) geographic segregation of species in the Desolation Canyon area is noted. Morphometric analysis argues against a hybrid origin for seminuda as postulated in the biochemical study (Rosenfeld and Wilkinson, 1989, above) and states that infraspecific variation as opposed to hybridization may be responsible for problematic intermediate specimens encountered and that hybrids are rare. The manuscript is generally too preliminary and disorganized to discern much further information. 23