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MEPS 222:253-264 (2001)
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Abstract
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Fine-scale habitat selection of foraging bottlenose dolphins Tursiops truncatus near Clearwater, Florida
Mark C. Allen1,*, Andrew J. Read3, Jocelyn Gaudet2, Laela S. Sayigh1
1Department of Biological Sciences, and
2Department of Earth Sciences, University of North Carolina at Wilmington, 601 S. College Road, Wilmington, North Carolina 28403, USA
3Duke University Marine Laboratory, Nicholas School of the Environment, 135 Duke Marine Lab Road, Beaufort, North Carolina 28516, USA
*E-mail: allenmc1@aol.com
ABSTRACT: Previous studies have proposed that seagrass habitats, by supporting diverse and abundant fish assemblages, are preferred by foraging dolphins in coastal systems. To test this hypothesis, we (1) examined the fine-scale behavior of bottlenose
dolphins in relatively pristine and developed inshore sites near Clearwater Harbor, Florida, USA, and (2) used an otter trawl to sample potential fish prey in non-seagrass and seagrass habitats. In the pristine site, dolphins preferred dredged channel and
spoil-island habitats, while least preferring shallow seagrass habitats. In the developed site, foraging dolphins preferred the natural channel habitat, but exhibited little further selection. Therefore, the hypothesis that dolphins prefer seagrass
habitats while foraging was rejected. Feeding frequency was significantly associated with diel state, with foraging peaking at dawn and decreasing throughout the day. Dolphin group size was negatively correlated and nearest neighbor distance positively
correlated with feeding frequency. Analysis of trawl data focused on the pinfish Lagodon rhomboides which dominates the diets of dolphins in west Florida. The relative abundance of pinfish was significantly greater and standard lengths
significantly less in seagrass than in non-seagrass habitats. Dolphins therefore forage in non-seagrass habitats where 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 acoustically. Thus, the importance of seagrasses to the health of coastal dolphins is probably indirect, as seagrasses support fish populations on which dolphins rely.
KEY WORDS: Tursiops truncatus · Foraging strategy · Prey availability · Diel patterns · Pinfish Lagodon rhomboides
Full text in pdf format
Published in MEPS Vol.
222
(2001) on November 5
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2001
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