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transported from habitats that are more compartmentalized between species will likely exploit a broader niche in a more depauperate host community. Authors have long since commented on the deleterious effects that introduced and invasive species have on host ecosystems (Elton 1958, Lachner et al. 1970, Magnuson 1976, Ross 1991). Any new biological addition to an aquatic ecosystem will result in a modification of that ecosystem (Courtenay and Hensley 1980). Introductions into undisturbed habitats require the competition of space and food (Herbold and Moyle 1986). Thus, native individuals cannot reach maximum probabilities of survival and reproduction in the presence of introduced competitors (Murray 1986). This implies that direct or indirect competition will occur with resident species in the host ecosystem (Courtenay and Hensley 1980). Reviews of most exotic fishes indicate some undesirable effect on native fish assemblages (Ross 1991). Several outcomes can result from the introduction of non-indigenous species. Introduced species may fail to become established, become established with varying influences on sympatric species, and full establishment causing the displacement of the native species (Courtenay and Hensley 1980, Ross 1986, Walser et al. 2000). Ecological interactions among the native and nonnative species will dictate the outcome of an introduction. The degree of success obtained by a nonnative in displacing native species will play a large roll in how greatly the host system is affected. Nonnative species success can be directly or indirectly affected by a variety of biotic and abiotic interactions in the new environment (Angermeier and Winston 1998, Mooney and Cleland 2001). As environmental stability and food availability increase, niche breadths should decrease and 3
species diversity should increase (MacArthur and Levins 1967). Therefore, biotic factors, abiotic factors, or both could control a system’s species assemblage (Ross 1991). This depends mainly on the population stability of those species as controlled by environmental stochasticity and competition amongst species within that assemblage (Ross 1991). More stable aquatic environments (communities at equilibrium) would more likely be controlled primarily by competitive factors between species. However, those that experience harsh environmental fluctuations (communities not at equilibrium) would likely be primarily influenced by abiotic factors such as high flows in aquatic systems (Ross 1986, Freeman et al. 1988, Ross 1991). It is reasonable to assume that highly invadable aquatic systems will share many of these biotic/abiotic factors thought to increase the chances of successful invasions. Due to the fact that this thesis is solely directed towards interactions between small, non-piscivorous fishes, we should be most concerned with factors regulating the ecological interactions between those species. Many of these factors will be discussed in greater detail at this time. Abiotic factors include environmental conditions (water quality, climate, geology, gradient, flow, etc.), suitable habitat availability, watershed connectivity, and geographical isolation. However, the biology of a given species will determine whether or not these abiotic factors will be beneficial or deleterious. In order for aquatic invasions to occur the introduced environment must be suitable for that species’ survival. The more suitable the introduced environment is for nonnative introductions, the more susceptible the native assemblage is to change after that species has become established. Fluctuating environmental conditions can alter the state of environments to benefit or inhibit the colonization of introduced species. It has been stated that climate 4
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: In order for similar species to avo
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 and 46: native species pairs were partially
Page 47 and 48: interspecific separation of vertica
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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