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vg2 The Soulhu~estnn Nattnafist vol. 28, no. 2 <br />Indigenous minnows and suckers of southwestern North American have <br />aeen essentially free of the influence of other major groups of fishes, espe- <br />cially Perciformes, for millenia. It is my impression, based on field observa- <br />tions, that they are naive toward predators, showing little avoidance even <br />when under attack. Predator-avoidance responses seem quickly learned in <br />salmonid fishes (Patten, 1977), and would logically be so in most species, or <br />should be strongly selected for in a relatively simple system and given ade- <br />quate time. However, unique features o[ present environmental changes <br />include great speed of occurrence and a great diversity of predatory species. <br />Declines in the western fauna are directly proportional to establishment o[ <br />predatory non-native fishes (Minckley and Deacon, 1968; Hubbard, 1980). <br />Most o[ the these are lentic in habitat preferences, and introductions of such <br />species into the region have succeeded as a result o[ the construction o[ suit- <br />ably stable reservoirs. Extirpation of now re-established families such as <br />Esocidae, Centrarchidae, and Ictaluridae from western North American <br />before Plio-Pleistocene times has been attributed to a reduction in non- <br />erosive, lentic or semi-lentic, lowland habitats, following mountain building <br />(Miller, 1959). Reservoirs and stabilized flows again allow species of those <br />families to pourish when introduced. Other alien, often piscivorus fishes <br />such as cichlids, percichthyids, percids, and poeciliids now also have been <br />introduced. 41'estern rivers that remain unmodified resist incursions and con- <br />tinuous occupation by other than native Eish species (Moyle and Nichols, <br />1973; Moyle, 1976; orig. data), with notable exceptions being generalized, <br />s[ream•adapted fishes like red shinrr, carp, and channel and flathead (Pylo- <br />dictis olivaris) catfishes. The abundance of reservoirs, however, provides a <br />constant source of introduced fishes for rivers (Molles, 1980), so that even <br />when riverine reproduction is lacking or minimal, populations may persist. <br />Interactions of native and non-native animals may resul[ in.elimination of <br />one or the other. Generalization on these interactions commonly include <br />nebulous statements of competition, both by myself and others, to help <br />explain declines in western fishes. However, 1 now consider competition for <br />resources that are in short supply a secondary cause o[ extirpation. Exclud- <br />ing special cases such as genetic swamping of endemic trouts by non-native <br />trouts (Rinse and Minckley, 1983), and cold water below dams that termi- <br />nates reproduction, declines in native fish populations are largely attributa- <br />ble to predation by adults or juveniles of introduced kinds upon early lite- <br />history stages of indigenous forms (Myers, 1965; Minckley, 1973; Minckley et <br />al., 1977: McAda and Wydoski, 1980; Me[fe et al., 1982). The primary impact <br />of man's development of reservoirs has provided habitat for predators as a <br />secondary, but now prevalent, force in extirpation of native fishes. Ova are <br />directly eaten by offshore predators such as carp and channel catfish. Shore- <br />line and backwater habitats once exclusively available to non-piscis'orous <br />juveniles of suckers and minnows are now inhabited by young centrarchids <br />and mosquitolish, and others. Predation by these introduced animals des- <br />troys, the native faunal elemems. I[ is predictable, as theory and practice <br />demonstrating the role o[ predation in shaping animal communities <br />matures (Macao, 1977; Zaret, 1980), that predation by introduced species on <br />"naive" prey will be recognized as a major force in faunal change (e.g. Eck- <br />hardt, 1972; Diamond and Veitch, 1961; Simberioff, 1981). <br />May 1989 Minckley-Slams o[ Razorback Sucker 189 <br />Permits (or collecting were granted by AGFD, and some data on native fishes were supplied by <br />James Brooks, Thomas Liles, and William Silrey of that organization, or are from Dingell- <br />Johnson Reports produced by that Department. Kraig 8urksuand, NGFD, assisted in collecting in <br />that state, and Jerry Burton, L'SFK'S, held a permit (PRT 2-2588) for collection of bonytail chub. <br />Erir Gustavson, ASII, assisted in collection of data, especially on sexual dimorphism and lerun- <br />diry, in 1975-77. Mark Fredlake, ASU, examined scales and auempted aging of razorback surkers. I <br />sincerely thank all persons cited as "personal communication" in text for their help, without it <br />this compilation could not have been done. J. Collins, D. Hendrickson, D. Kubly, W. Loudermilk, <br />P. Marsh, G. Me[fe, and E. Milstead read the manuscript and provided comments which improved <br />it substantially. <br />Funding was through the USFN'S, Albuquerque, New Mexico, in 1975.76 (Contract No. 19-16 <br />0002.3585, with ASU), by ASIJ and from my personal resourms in 1977 and 1974, and again by the <br />USFN'S in 1979-82. Publicayion costs also were partially defrayed by USFN'S funds. <br />LITERATURE CITED <br />Aeeorr, C. C. 1861. Descriptions of lour new species of North American Cyprinidae. Prot. <br />Phila. Acad. Nat. Sci., 12 (1860): 473-474. - <br />ANONYMOUS. , (973. Lake Mead bass study. Environ. Off., U.S. Bur. Redam., Lower Colorado <br />Reg. O(L, Boulder City, Nev. <br />-. 1980. Special report on distribution and abundance of fishes of the lower Colorado <br />Rivet Final Rept. Water Power Aes. Ser., Contr. No. 9-07-03-X0066, U.S. Fish Wildl. <br />Ser., Phoenix, Ariz. <br />-. 1981. Aquatic study of the lower Colorado River. Final Rept. Water Power Res. Ser., <br />Conte No. 9.07-OS-X0066. 0.S. Fish Wildl. Ser., Phoenix, Ariz. <br />BACENAL, T. G., AND E. BxnuM. 1978. Eggs and early life history. Pp. 165-201, in IBP Hand- <br />book A`o. 3, Methods (or Assessmem of Fish Production in Freshwaters (T- $agenal ed.) <br />Blackwell Sci. Publ., Oxford-Edinburgh, Engl, <br />HAart.en, J. P. IB54. Personal Naaative of Exploration and Incidents in Texas, New Mexico. <br />California, Sonora, and Chihuahua. D. Appleton, Co., N. Y., N. Y. <br />HEn NxE, R. J. 1980. Chapter )0. The impacts of habitat alterations on the endangered and <br />threatened fishes of the upper Colorado River basin. Pp. 204.216, in Energy development <br />in the southwest. Problems of water, fish and x•ildli(e in the upper Colorado River basin. <br />Volume two. Resources for the future (W. O. Spofford, Jr., et a1., eds.) Res. Pap. R-I8, <br />Washington, D.C. <br />BELAND, R. D. 1959. The effect of channelization on the fishery of the lower Colorado River. <br />Cali[. Fish Game 39: 137•] 39. <br />BRANSON, B. A. 1961. Observations on the distribution of nuptial tubercles in some catostomid <br />fishes. Trans. Kans. Acad. Sci., 64: 560.372. <br />-. 1966. Some rare and vanishing fishes. Bioscience, 16: 611-615 <br />BnowN, D. E., AND C. H. LowE. 1978. Biotic communities of the southwest. 1/5DA For. Ser. <br />Gen. Terh. Rept. RM-91: Map. Rocky Mtn. For. Range Exp. Sta., Ft. Collins, Colo. <br />BuexztAAt, D. E. 1972. Channel changes of the Gila River in Safford Valley, Arizona. U.S. <br />Geol. Sur. Prof. Pap., 655-B: 1-29. <br />CxAMaEautN, F. M. 1904. Notes on fishes collected in Arizona, 1909. U.S. Nat. Mus., Washing- <br />ton, D.C. (unpubl. ms.). <br />COLEMAN, G. A. 1929. A biological survey o[ the Salton Sea. Certif. Fish Game, 15:218-227. <br />DIAMOND, J. M., AND C. R. VEtree. 198(. Extinctions and invoductions in the New 7raland <br />aei(aunar cause and e(tecd Science, 221: 999-501. <br />DaL, W. A. 1949. The (fishery of the lower Colorado River. Calif. Fish Game, 30: 109-21 I. <br />Dooeus, P. A. 1952. Notes on the spawning of the humpback sucker, Xyraurhen lexanus <br />(Abbott). Cali[. Fish Game, 38: 149-155. <br />EexeAxor, R. G. 1972. Introduced plants and animals in the Galapagos Islands. BioScience, <br />22: 585-590. <br />EwsoN, D. N. 1980. Lever to the editor. Wildlife Views, 29:2. Ariz. Game Fish Dept., Pho- <br />enix, Ariz. <br />EVERMANN, B. N'. 1916. Fishes of the Sahon Sea. Gopeia, 1916: 61-63. <br />EVERMANN, B. N'., AND C. Rorrea. 1895. Fishes of the Colorado Basin. U.S. Fish Comm. <br />Bull„ 14 (1894): 473-486. <br />