Fine-scale habitat selection of foraging bottlenose dolphins Tursiops truncatus near Clearwater, Florida

Previous studies have proposed that seagrass habitats, by supporting divers e and abundant fish assemblages, are preferred by foraging dolphins in coas tal systems. To test this hypothesis, we (1) examined the fine-scale behavi or of bottlenose dolphins in relatively pristine and developed inshore site s near Clearwater Harbor, Florida, USA, and (2) used an otter trawl to samp le potential fish prey in non-seagrass and seagrass habitats. In the pristi ne site, dolphins preferred dredged channel and spoil-island habitats, whil e least preferring shallow seagrass habitats. In the developed site, foragi ng dolphins preferred the natural channel habitat, but exhibited little fur ther selection. Therefore, the hypothesis that dolphins prefer seagrass hab itats while foraging was rejected. Feeding frequency was significantly asso ciated with diel state, with foraging peaking at dawn and decreasing throug hout the day. Dolphin group size was negatively correlated and nearest neig hbor distance positively correlated with feeding frequency. Analysis of tra wl data focused on the pinfish Lagodon rhomboides which dominates the diets of dolphins in west Florida. The relative abundance of pinfish was signifi cantly greater and standard lengths significantly less in seagrass than in non-seagrass habitats. Dolphins therefore forage in non-seagrass habitats w here fish prey is both larger and perhaps more available, Although seagrass habitats support greater abundance of smaller fishes, they also provide a structural refuge which obscures fishes both visually and possibly acoustic ally, Thus, the importance of seagrasses to the health of coastal dolphins is probably indirect, as seagrasses support fish populations on which dolph ins rely.