An Experimental Study of Vertical Habitat Use and Habitat Shifts in ...

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Aquaria setup In the laboratory, fishes were separated by species and transferred to aquaria and holding tanks (with bottom substrates of < 6.4 mm diameter from the East Fork Greenbrier River). Four 246 L (65 gal) glass aquaria (91.5 mm x 45.8 mm x 53 cm) and two 379 L (100 gal) reservoirs were used as observation and holding tanks, and were all connected in a recirculation system with a 379 L sump. The sump was connected to a sequence pump that recirculated water to all aquaria and holding tanks at a rate of approximately 2.6 L/min. Carbon filters, bio balls, substrate vacuum, fresh water substitutions, and frequent monitoring were employed to maintain appropriate water quality. Salinity levels were kept at 2-3 ppt and water temperature varied between 18.4 - 24°C throughout all trials. Fishes were fed daily with frozen bloodworms (genus Glycera) and frozen brine shrimp (genus Artemia). Photoperiod was maintained with florescent lights (plant bulbs) and an electric timer (14 hr light, 10 hr dark). Fishes were given a minimum of one week acclimation time before data collection (but all individuals were actively feeding within aquaria on the same day as transport). Allotopic and syntopic experiments Aquaria-based experiments were designed to examine vertical distribution shifts of two native minnows (C. spiloptera and N. scabriceps) in response to the presence of non-native congeners (C. galactura and N. telescopus). Water column positions of each species within aquaria were observed separately (allotopic trials) and concomitantly for each congeneric native/non-native species pair (syntopic trials). Six vertical categories described positions of individual fishes within the water column of aquaria (similar to that of Gorman 1988). Vertical position categories (each 8.5 cm high) were defined as 35
enthic, near-benthic, lower-pelagic, mid-pelagic, upper-pelagic, and surface pelagic (Gorman 1988). Position locations of individual fishes were determined by horizontal lines (8.5 cm intervals on white poster board) located on the backside of each aquaria. For both Cyprinella and Notropis pairs, species were segregated into three groups (20 individuals of each species in three separate tanks). Then, I conducted a total of nine trials with a crossover-based design where each native species group of 20 individuals was rotated with each congener group of 20 individuals and with each aquarium (syntopic trials). As a control, the positions of 40 individuals were observed for each species without the presence of its congener (allotropic trials). For allotopic trials, I used one group (40 individuals total) of each Notropis species (total of two tanks) and two groups (80 individuals total) of each Cyprinella species (total of four tanks). Fewer Notropis groups in allotopic trials resulted from a lower number of available individuals of N. scabriceps. The use of equal numbers of individuals of each species (n=20) within tanks and equal numbers of individuals among tanks (n=40) controlled for effects of disproportionate abundances. Video cameras recorded individual positions during allotopic trials. Before data collection, 45 minutes of tape elapsed to allow individuals to adjust to the video camera and tripod. It was later realized, however, that camera recordings would not allow adequate resolution of two species during syntopic trials. Therefore, a tarpaulin was draped from the lab ceiling in front of aquaria to reduce observer effects, and individual fish positions were viewed through rectangular slits in the tarpaulin. For camera recordings and direct observations, individual fish positions were collected at least 30 seconds apart until 160 (allotopic) or 100 (syntopic) positions were recorded per trial. 36
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: native cyprinids on their native co
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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