Qualitative Characters, Identification of Colorado River Chubs (Cyprinidae: Genus Gila) and the "Art of Seeing Well"

Abstract

Qualitative scoring is frequently overlooked in preference to counts or measurements of individual characters, particularly for species whose overlap in morphology makes clear separation difficult. Quantitative measurements and counts of single characters were compared to qualitative rankings of selected morphological features of chubs (genus Gila) from the Yampa River, Colorado. Data were collected by technicians with no specialized training in systematics. A high degree of morphological variability confounded identification using the quantitative data set, while principal components analysis of qualitative data clearly separated Gila cypha (humpback chub) and G. robusta (roundtail chub). Totals of 32 G. cypha and 336 G. robusta were identified; no intermediates were indicated. We thus demonstrate that scoring of complex characteristics is useful for endangered fishes that must be minimally handled to insure uninjured release. The clean separation of syntopic G. cypha and G. robusta supports protection of the lower Yampa River, the only location in the upper Colorado River basin in which apparent hybridization between the endangered G. cypha and its congeners remains to be documented. The art of seeing well, or of noticing and distinguishing with accuracy the objects which we perceive, is a high faculty of the mind, unfolded in a few individuals, and despised by those who can neither acquire it, nor appreciate its results. Rafinesque (1820), Ichthyologia Ohioensis.