Abstract
Extant fishes endemic to the upper Colorado River of the American southwest include only cyprinids and catostomids. A curious attribute in species of both groups is the presence of a large nuchal hump. Largest cyprinid humps occur in humpback chub, Gila cypha, and largest catostomid humps occur in razorback sucker, Xyrauchen texanus. Several authors have suggested the humps confer a hydrodynamic advantage to life in fast flow, but this premise has not been confirmed with experimental work. To test the role of humps in Colorado River fishes, we subjected whole-body casts of preserved specimens with humps and with humps removed to controlled flows in an experimental tank. These tests confirmed that humps increased drag coefficients for X. texanus and G. cypha with no additional lift component. High energetic costs of locomotion and position-holding with a large hump, and the additional metabolic expense of forming large humps, suggest that the humps are not relict structures. Instead, we argue that these large humps represent convergent evolution prompted by predation from a cyprinid piscivore. Colorado pikeminnow, Ptychocheilus lucius, top piscivore in the Colorado River system, is the only native fish capable of consuming large X. texanus and G. cypha, and it also is sympatric with them. However, lack of jaw teeth and a relatively small jaw gape limit the maximum prey size that P. lucius can consume. Based on gape size, about 55% of X. texanus and 71% of G. cypha could be consumed by even the largest P. lucius. However, vulnerability would increase to 73 and 83% respectively if these species did not have humps. Coevolution tends to favor predator defense mechanisms in prey most vulnerable to such a voracious predator. Development of a large nuchal hump provides a deep body that is difficult or impossible for P. lucius to ingest.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Adler, F.R. & C.D. Harvell. 1990. Inducible defenses, phenotypic variability and biotic environments. Trends Ecol. Evol. 5: 407–410.
Alexander, D.E. 1990. Drag coefficients of swimming animals: effects of using different reference areas. Biol. Bull. 179: 186–190.
Brönmark, C. & J.G. Miner. 1992. Predator-induced phenotypical change in body morphology in crucian carp. Science 258: 1348–1350.
Brönmark, C. & L.B.Pettersson. 1994. Chemical cues from piscivores induce a change in morphology in crucian carp. OIKOS 70: 396–402.
Carlson, C.A. & R.T.Muth. 1989. Colorado River: lifeline of the American Southwest. Can. J. Fish. Aquat. Sci. Spec. Publ. 106: 220–239.
Cole, G.A. 1994. Textbook of Limnology, Waveland Press, Prospect Heights, Illinois. 412 pp.
Converse, Y.K., C.P. Hawkins & R.A. Valdez. 1998. Habitat relationships of subadult humpback chub in the Colorado River through Grand Canyon: spatial variability and implications of flow regulation. Regul. Rivers: Res. Manage. 14: 267–284.
Denny, M.W. 1988. Biology and the Mechanics of the Wave-swept Environment, Princeton University Press, Princeton, New Jersey. 329 pp.
Diana, J. 1995. Biology and Ecology of Fishes, Cooper Publishing Group, Indiana. 441 pp.
Gillen, A.L., R.A. Stein & R.F. Carline. 1981. Predation by pellet-reared tiger muskellunge on minnows and bluegills in experimental systems. Trans. Am. Fish. Soc. 110: 197–209.
Hambright, D.K. 1991. Experimental analysis of prey selection by largemouth bass: role of predator mouth width and prey body depth. Trans. Am. Fish. Soc. 120: 500–508.
Harvell, C.D. 1990. The ecology and evolution of inducible defenses. Quart. Rev. Biol. 65: 323–340.
Havel, J.E. 1987. Predator-induced defenses: a review.pp.263–278. In: W.C. Kerfoot & A. Sih (eds.) Predation: Direct and Indirect Impacts on Aquatic Communities, University Press of New England, Hanover, New Hampshire.
Havel, J.E. & S.I. Dodson. 1987. Reproductive costs of Chaoborus-induced polymorphism in Daphnia pulex. Hydrobiologia 150: 273–281.
Hawkins, J.A. 1992. Age and growth of Colorado squaw fish from the upper Colorado River Basin, 1978 –1990. M.S. Thesis, Colorado State University, Fort Collins.75 pp.
Hoetker, G.M. & K.W. Gobalet. 1999. Fossil razorback sucker (Pisces: Catostomidae, Xyrauchen texanus) from southeastern California. Copeia 1999: 755–759.
Jordan, D.S. & B.W. Evermann. 1896. The fishes of North and Middle America. Bulletin of the United States National Museum 47, Smithsonian Institute, Washington,DC. 3313 pp.
Kaeding, L.R. & M.A. Zimmerman. 1983. Life history and ecology of the humpback chub in the Little Colorado and Colorado Rivers of the Grand Canyon. Trans. Am. Fish. Soc. 112: 577–594.
Karp, C.A. & H.M. Tyus. 1990. Humpback chub, Gila cypha, in the Yampa and Green Rivers, Dinosaur National Monument, with observations on roundtail chub, Gila robusta, and other sympatric fishes. Great Basin Nat. 50: 257–264.
Lampert, W. & U. Sommer. 1997. Limnoecology: The Ecology of Lakes and Streams, Oxford University Press, New York. 382 pp.
La Rivers, I. 1962. Fishes and Fisheries of Nevada, University of Nevada Press, Reno. 782 pp. (Republished by the Nevada State Fish and Game Commission, 1994.)
Lively, C.M. 1986. Competition, comparative histories, and maintenance of shell dimorphism in a barnacle. Ecology 67: 858–864.
Marsh, P.C. & W.L. Minckley. 1989. Observations on recruitment and ecology of the razorback sucker: Lower Colorado River, Arizona –California –Nevada. Great Basin Nat. 49: 171–178.
Meretsky, V.J., R.A. Valdez, M.E. Douglas, M.J. Brouder, O.T. Gormon & P.C. Marsh. 2000. Spatiotemporal variation in length-weight relationships of endangered humpback chub: implications for conservation and management. Trans. Am. Fish. Soc. 129: 419–428.
Miller, R.R. 1946. Gila cypha, a remarkable new species of cyprinid fishes from the Colorado River in Grand Canyon, Arizona. J. Washington Acad. Sci. 36: 409–415.
Miller, R.R. 1958. Origins and affinity of the freshwater fish fauna of Western North America. pp.187–222. In: C.L. Hubbs (ed.) Zoogeography, Publication 51, Washington DC.
Miller, R.R. 1961. Man and the changing fish fauna of the American Southwest. Papers Michigan Acad. Sci. Arts Lett. 46: 365–404.
Minckley, W.L. 1983. Status of the razorback sucker, Xyrauchen texanus (Abbott), in the Lower Colorado River Basin. Southwest. Nat. 28: 165–187.
Minckley, W.L., D.A. Henderson & C.E. Bond. 1986. Geography of western North American freshwater fishes: description and relationships to intracontinental tectonism. pp.519–613. In: C.H. Howcutt & E.O. Wiley (eds.) The Zoogeography of North American Freshwater Fishes, John Wiley and Sons, New York.
Minckley, W.L., P.C. Marsh, J.E. Bromes, J.E. Johnson & B.L. Jensen. 1991. Management toward the recovery of the razorback sucker. pp.303–357. In: W.L. Minckley & J.E. Deacon (eds.) Battle Against Extinction: Native Fish Man-agement in the American Southwest, University of Arizona Press, Tucson.
Moyle, P.B. & J.J. Cech,Jr. 2004. Fishes: An Introduction to Ichthyology,5th edition, Prentice-Hall, Upper Saddle River, New Jersey. 612 pp.
Nilsson, P.A., C. Brönmark & L.B. Pettersson. 1995. Benefits of a predator induced morphology in crucian carp. Oecologia 104: 291–296.
Pettersson, L.B. & C. Brönmark. 1999. Energetic consequences of an inducible morphological defense in crucian carp. Oec-ologia 121: 12–18.
Schlichting, H. 1979. Boundary Layer Theory, McGraw-Hill, New York.817 pp.
Sigler, W.F. & J.W. Sigler. 1996. Fishes of Utah,a Natu-ral History, University of Utah Press, Salt Lake City. 375 pp.
Smith, G.R. 1981. Effects of habitat size on species richness and adult body sizes of desert shes.pp.125–172. In: R.J. Nai-man & D.L. Soltz (eds.) Fishes in North American Deserts, John Wiley and Sons, New York.
Stemberger, R.S. & J.J. Gilbert. 1987. Defenses of planktonic rotifers against predators.pp.227–239. In: W.C. Kerfoot & A. Sih (eds.) Predation: Direct and Indirect Impacts on Aquatic Communities, University Press of New England, Hanover, New Hampshire.
Tyus, H.M. 1987. Distribution, reproduction, and habitat use of the razorback sucker in Green River, Utah, 1979 –1986. Trans. Am. Fish. Soc. 116: 111–116.
Tyus, H.M. 1998. Early records of the endangered fish Gila cypha (Miller) from the Yampa River of Colorado, with notes on its decline. Copeia 1998: 190–193.
Tyus, H.M. & C.A. Karp. 1990. Spawning and movements of razorback sucker, Xyrauchen texanus, in the Green River Basin of Colorado and Utah. Southwest. Nat. 35: 427–433.
Vogel, S. 1994. Life in Moving Fluids: The Physical Biology of Flow, Princeton University Press, Princeton, New Jersey. 467 pp.
Webb, P.W. 1975. Hydrodynamics and energetics of fish propulsion. Bull. Fish. Res. Board Can. 190: 1–158.
Webb, P.W. 1984. Body form, locomotion and foraging in aquatic vertebrates. Am. Zool. 24: 107–120.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Portz, D., Tyus, H. Fish humps in two Colorado River fishes: a morphological response to cyprinid predation?. Environmental Biology of Fishes 71, 233–245 (2004). https://doi.org/10.1007/s10641-004-0300-y
Issue Date:
DOI: https://doi.org/10.1007/s10641-004-0300-y