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. . .... .- .. , J .. HOLDEN, ET AL.: THREATENED FISHES OF UTAH S6 group. Any further alteration of the Colorado River System should be discouraged. Virgin River Fishes Gila Tobusta seminuda- Virgin River Chub Status: Endangered subspecies Description: Taxonomy of the Virgin River chub is uncertain, as its asso- ciation with the Pahranagat roundtail (G.T. joTdani)and roundtail chub (G.T. Tobusta) is unclear. This discussion is limited to the roundtaiI of the Virgin River, G.T. seminuda. Descriptions of this form are lacking; Holden and Stalnaker (1970) examined six specimens and Miller (1946) examined the five type specimens. Major differences between G.T. seminuda andG.T. Tobusta were dorsal fin rays 9.10 (9.3) and 9 respectively, gill rakers 24-31 (27.7) and 20-28 (24) respectively, and vertebrae 40-42 (40.7) and 41-44 (42.2) respectively. The original description of seminuda stressed an absence of scales on ventral and dorsal areas. This character was found to be variable in Gila robusta throughout the Colorado basin (Holden and Stalnaker, 1970). The Virgin River chub is very silvery, as are other Virgin River fish. Documentation: Original range of the Virgin River chub was the Virgin River up to La Verkin Spring near Hurricane, Utah. Much of the lower Virgin River is now flooded by Lake Mead. The chub was very abundant in the Utah section of the river in the late 19601. Recent studies by Cross and Deacon (1973) did not find this form above the mouth of Beaver Dam Wash, Arizona, or in Utah except at La Verkin Spring. They found it to be more common below Beaver Dam Wash in Arizona and Nevada. It is based on this recent and apparently drastic reduction in the Utah and part of the Arizona population and the loss of habitat due to Lake Mead that the endangered status is believed warranted. Dr. James Deacon (University of Nevada, Las Vegas) considers this chub the most threatened of the Virgin River fishes. FactoTs Influencing Decline: Factors causinc the recent decrease in Virgin River chub populations are unknown. Plagopterus aTgentissimus- Woundfin Status: Endangered species Description: The wound fin is a member of the tribe Plagopterini, a unique group of minnows endemic to the Lower Colorado River basin. This tribe is characterized by spines in the dorsal and pelvic fins. The woundfUl is .. 'W',' ~ . +- .; , "