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INFLUENCE OF SPAWNING GROUP SIZE AND SPACE ON REPRODUCTION BY SHEEPSHEAD MINNOWS, CYPRINODON VARIEGATUS
Citation:
Cripe, G M., R L. Hemmer, AND L R. Goodman. INFLUENCE OF SPAWNING GROUP SIZE AND SPACE ON REPRODUCTION BY SHEEPSHEAD MINNOWS, CYPRINODON VARIEGATUS. Presented at SETAC World Congress, Portland, OR, November 14 - 18, 2004.
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Conference abstract
Description:
Cripe, G.M., R.L. Hemmer and L.R. Goodman. In press. Influence of Spawning Group Size and Space on Reproduction Variability of Sheepshead Minnows, Cyprinodon variegatus (Abstract). To be presented at the SETAC Fourth World Congress, 14-18 November 2004, Portland, OR. 1 p. (ERL,GB R1007).
The evaluation of some chemicals for adverse effects on endocrine-mediated processes may include both preliminary screening tests and two-generation tests with various wildlife species. The sheepshead minnow is one of the species proposed for these two-generation tests and a series of experiments are being conducted to determine the feasibility and to reduce the variability of endpoints. The development of methods for multiple generation exposure of fishes will include survival, growth and reproduction, ultimate measures of population impacts. Because natural spawning, insuring reproductive success, generally occurs in open space with self-selection of mate, the design of laboratory tests must limit the influence of confined space and artificial mate selection on egg production. Experiments were conducted with four sizes of spawning chambers, three ages of mature sheepshead minnows and three ratios of males to females, to identify designs which would reduce variability in egg production. Preliminary results with two replicates of three chamber designs identified wide variability of daily egg production. Older (180 day) fish placed in cylindrical (28.6 cm diameter) and square spawning chambers (28.0 x 30.5 cm) at a ratio of three females with two males produced an average of 40.5 (? 28.6) and 83.0 (? 28.6) eggs/day, respectively. Similar age and size spawning groups in rectangular chambers (28.0 x 19.0 cm) produced an average of 39.2 (? 18.1) eggs/day. In spawning trials with newly matured adults (68-70 days, 3.4 cm total length) the males were found to be overly aggressive and the survival of females in the spawning groups and egg production were adversely affected. Of the spawning combinations tested, groups of three females and two males resulted in the least aggression and mortality. This combination, which also decreases laboratory in-breeding, is likely the best choice for measuring reproductive potential.