Matthew Behum, Colgate University

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Abstract:

To fully understand interannual variations in the sizes of fish populations, the relationship between abiotic (density-independent) and biotic (density-dependent) factors must be analyzed. Moreover, particular attention must be given to the influences of physical factors in the field, and how it influences fish behavior, and ultimately larval recruitment. Small-scale turbulence in the field has been found to increase prey encounter with planktonic predators. Feeding success, however, is limited to a certain threshold of turbulence for visual predators, where the probability of successful seizure of prey eventually decreases with increasing turbulence. The effects of turbulence on non-visual predators is not investigated as fully as the effects of turbulence on visual predators, but is a worthy topic to completely understand microscale turbulence effects on an entire food web. The purpose of this investigation is to analyze the effects of varying amounts of small-scale turbulence on the feeding success of the non-visual ctenophore predator, Mnemiopsis leidyi. Small ctenophores were exposed to varying amounts of turbulence in a novel turbulence chamber apparatus while being fed an identical Artemia salinia nauplii concentration for each turbulence condition. Ingestion rates were analyzed as the mean naupllii/gut, and standard error bars were used to compare ingestion rates among all tested turbulences (0 mm/s- 26.2 mm/s). It was observed that no significant effect of turbulence on ingestion rate existed, as a non-linear relationship was discovered. This counters expectations as non-visual predators were proposed to encounter continually increasing feeding success with increasing turbulence due to ingestion based on contact, not visual pursuit. Further turbulence investigations concerning other non-visual predators should be undertaken to confirm these findings.