HCNSO Student Theses and Dissertations

Defense Date

1-2015

Document Type

Thesis

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

David W. Kerstetter

Second Advisor

Richard E. Spieler

Third Advisor

Tracey T. Sutton

Abstract

Great barracuda Sphyraena barracuda is a large predatory teleost found circumglobally, other than the Eastern Pacific Ocean. The species is commonly caught by both recreational and commercial fishermen as bycatch while targeting other, more economically or recreationally valuable fishes. This species also exhibits an ontogenetic shift in habitat, with juveniles inhabiting mangrove and seagrass habitats, while adults live near offshore reefs and associated structure.

This thesis consists of two separate studies of S. barracuda: 1) feeding ecology along an ontogenetic gradient and 2) habitat utilization of as derived through electronic tagging. The first chapter of this thesis describes the feeding ecology of great barracuda in South Florida, with an emphasis on the determination of when the ontogenetic shift in diet occurs between habitats and individual fish sizes. Specimens were collected primarily by seine net and hook-and-line fishing. The specimens were then dissected with the stomach contents examined. This study found that the ontogenetic diet shift in great barracuda begins around the second year, and that juveniles and adults are opportunistic predators with a wide diversity of teleost and crustacean prey items within the selected habitat. The second chapter of this thesis describes the habitat utilization and vertical movements of two great barracuda off of South Florida interpreted from data acquired from pop-up satellite archival tags (PSATs). This study found that large (>100 cm) great barracuda are capable of travelling hundreds of kilometers over a period of days to weeks. The results show that large great barracuda can tolerate temperatures ranging from 17.8° C to 31.3° C, and are capable of diving to depths greater than 175 m. It was also found that there was a significant difference in time spent at depth, with greater depths being inhabited more frequently at night.

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