Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

John W. Fleeger

Abstract

Predator-prey relationships between post-larval and juvenile teleosts are greatly influenced by the manner in which feeding behavior of fish interacts with the behavior of meiofaunal prey. Juvenile starry flounder (Platichthys stellatus Pallas) in a southeastern Alaskan bay fed disproportionately on the harpacticoid copepod Microarthridion littorale (Poppe), particularly on males. This apparent selectivity was not due to differing vertical distribution of harpacticoid species or to feeding in other locations. Comparison of ingested prey to harpacticoid assemblages collected by various techniques (including near-bottom collections) suggested that the prey selection shown by starry flounder may be the result of emergent behavior of its harpacticoid prey. Species-level prey identifications indicated that harpacticoid density at the site was not limited by flounder predation. Post-larval and juvenile spot (Leiostomus xanthurus Lacepede) from the northern Gulf of Mexico showed ontogenetic changes in prey selection. Post-larval spot preyed on a copepod assemblage most closely resembling that collected in settlement/bedform traps, suggesting that they also utilized prey in the near-bottom waters. At larger sizes, the diet of juvenile spot was more similar to sediment-dwelling assemblages. This switch coincided with a dramatic increase in the number of nematodes in the diet. In laboratory experiments, juvenile spot demonstrated an ability to recognize and selectively feed in meiofaunal aggregations similar to those formed by meiofauna in the field. This utilization was manifested in a greater proportion of feeding strikes allocated to high density treatments and an increased processing time of feeding strikes taken in such areas. Stomach contents of spot contained a significantly higher proportion of harpacticoid copepods than did the sediments on which they fed. The ability of juvenile spot to recognize and selectively utilize aggregations may be a means of increasing feeding efficiency, perhaps prolonging the period when juveniles subsist on a diet of meiofaunal-sized prey. A greater understanding of meiofaunal behavior, particularly that of hyperbenthic meiofauna, is necessary to more clearly understand the nature of predator-prey interactions between fish and meiofauna.

Pages

131

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