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elationship between mouth position and habitat use in fishes. Benthic-oriented fishes typically have inferior of subterminal mouths and pelagic fishes have terminal or supraterminal mouth positions (Mendelson 1975). Notropis telescopus and C. spiloptera were more pelagically-oriented, each having mouths that are more terminally-positioned than their congeneric counterparts. Mouth position is generally viewed as a phylogenetic or historical constraint, with a strong proximate influence on habitat use. Increased integration during syntopy as reported in this study provides evidence of a strong species interaction influence over morphologically-correlated use of habitat in cyprinids. In contrast to segregation by competitive displacement, studies have documented integration through mixed-species shoals (Magurran and Pitcher 1983, 1987, similar to mixed-species flocks of birds, Morse 1970). Previous interspecific contact may not be required for two species, such as a native/non-native species pair, to closely-associate and benefit symbiotically from interactions, such as by improved foraging success (Magurran and Pitcher 1983) or by predator avoidance (i.e., safety in numbers, Allan and Pitcher 1986, Mathis and Chivers 2003). Based on general observations during my experiments, the more pelagically-oriented species of each pair fed more aggressively during syntopic trials, hence, there was no qualitative evidence for a mixed-shoal advantage of foraging for both species. The number of individuals per tank in allotopic trials (n = 40) was equal to that of syntopic trials, so the data do not support evidence for an influence of density on syntopic integration, as one would expect from a “safety in numbers” explanation of predator avoidance. In conclusion, the laboratory-based experimental study demonstrates a difference in vertical use of habitat between two native/non-native congeneric pairs. The 41
interspecific separation of vertical habitat use (as found in allotopic trials) decreased during syntopic trials owing to an increase in interspecific integration. Based on concepts of competition, I expected segregation during syntopy as a mechanism to reduce competitive interactions. Integration of species during syntopic trials, however, may be interpreted as a predator avoidance behavior associated with mixed-species shoals. It is unknown if the native/non-native species of this study integrate and co-occur in mixedspecies shoals within the Greenbrier River system. Recent population assessments indicate disproportionate population sizes of these native and non-native minnows (Chipps et al. 1993b, Burns 2007), and additional research is needed to compare experimental results with native/non-native interactions occurring within the Greenbrier River drainage. 42
Page 1 and 2: An Experimental Study of Vertical H
Page 3 and 4: Acknowledgements I would like to th
Page 5 and 6: LIST OF TABLES Table 1. Results of
Page 7 and 8: In order for similar species to avo
Page 9 and 10: species diversity should increase (
Page 11 and 12: noting that the abundance of some s
Page 13 and 14: exhibited by species involved; the
Page 15 and 16: new environment (Dueser and Porter
Page 17 and 18: host environment, proposing that a
Page 19 and 20: Hybridization with introduced speci
Page 21 and 22: alteration may reduce the habitat s
Page 23 and 24: in the upper Greenbrier River and o
Page 25 and 26: ubiquitous, appearing in all channe
Page 27 and 28: Literature Cited Addair, J. 1944. T
Page 29 and 30: Gibbs, R. H. 1957. Cyprinid fishes
Page 31 and 32: Lobb, M. D., III. 1986. Habitat use
Page 33 and 34: Paybins, K. S., T. Messinger, J. H.
Page 35 and 36: Chapter 2: An Experimental Study of
Page 37 and 38: Introduction Non-native fishes nega
Page 39 and 40: native cyprinids on their native co
Page 41 and 42: enthic, near-benthic, lower-pelagic
Page 43 and 44: N. telescopus had modes in the lowe
Page 45: native species pairs were partially
Page 49 and 50: MacArthur, R. and R. Levins. 1967.
Page 51 and 52: Table 1. Results of Chi square Test
Page 53 and 54: Total Number of Occurrences 160 140
Page 55: Total Number of Occurrences 160 140

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