Influence of food and predation on the depth distribution of juvenile spot (Leiostomus xanthurus) in tidal nurseries

Abstract

Relative abundances of young-of-the-year (YOY) spot (Leiostomus xanthurus) sampled by trawling in two tidal creeks on Masonboro Island, North Carolina, were highest in the shallow creek margins. Abundances of benthic invertebrates sampled by cores in one of the study creeks, were also maximal at the creek margin. Polychaetes associated with the creek margin composed the largest fraction of spot diets, indicating spot located in the creek margins were in the area of highest food availability. Spot predators sampled by trawling and seining were uncommon and were primarily juvenile (75–200 mm total length) southern flounder (Paralichthys lethostigma), hake (Urophycis spp.), and bluefish (Pomotomus saltatrix). Large YOY spot experienced a size refuge from predation, as only small YOY spot were found in predator stomachs. In laboratory experiments testing the effects of the presence of a predator, food, or both food and predators on the depth distribution of YOY spot, food had a stronger effect on spot distributions than predators The results of field observations and laboratory experiments suggest food has the strongest effect on spot distribution in the field, and that food is relatively more important than refuge from predation to the nursery function of shallow estuarine habitats.