Date of Award

Fall 1991

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

M. J. Butler, IV

Committee Member

R. S. Birdsong

Committee Member

R. W. Alden, III

Call Number for Print

Special Collections LD4331.B46 M32


Test populations of different-sized guppies, Poecilia reticulata, were exposed to individuals of two natural predatory species, the pike cichlid Crenicichla a/ta and the killifish Rivulus harti, under conditions of varying prey (guppy) density and habitat complexity in the laboratory. Rivulus fed most frequently on newborn and juvenile guppies < 14 mm. Crenicichla consumed more and larger guppies than did Rivulus. The mean guppy size eaten by Crenicichla was dependent on the length of the individual predator, but as a group, the 15 Crenicichla tested were non-selective with respect to guppy size and gender. The prey gender preference of Rivulus could not he determined because they primarily ate immature guppies. High habitat complexity and a shallow water refuge reduced Crenicichla predation rates from 9.88 to 2.92 guppies/day, but did not change prey-size selectivity. Rivulus predation rates never exceeded 1.0 guppies/day, regardless of habitat complexity. Under test conditions which mimicked typical field conditions of habitat complexity and prey density, Crenicichla was a much more dangerous guppy predator than Rivulus. However, Rivu/us could he an important predator of immature guppies in situations where guppy densities are high and Rivulus are abundant.


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