Theses and Dissertations

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Defense Date

3-2013

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

David W. Kerstetter

Second Advisor

Patrick Hardigan

Third Advisor

Richard E. Spieler

Abstract

Understanding the life history of a species is essential for fully understanding its role within an ecosystem. However, many of the fish species of high ecological value have not been studied due to their less prominent roles in local recreational and commercial fisheries in comparison to other targeted species. This study describes the age and growth patterns of three small tuna species inhabiting South Florida waters: blackfin tuna Thunnus atlanticus, little tunny Euthynnus alletteratus, and skipjack tuna Katsuwonus pelamis. Tuna specimens were collected via donations obtained from various fishing tournaments and charter captains in the areas of the Florida Straits as well as hook-and-line by the Nova Southeastern University Oceanographic Center. Age was described via sagittal otolith deposition patterns. They were removed, dried, sectioned, and rings were counted as well as measured. Validation of the timing of ring deposits was done by marginal increment analysis. Growth parameters were determined by comparison of fish fork length to count measurements. This comparison via the Von Bertalanffy growth equation produced a growth rate for each species: blackfin, L = 95.34 cm, K = 0.28, and t0 = -1.53; little tunny, L = 77.93 cm, K = 0.69, and t0 = -0.69; and skipjack, L = 112.76 cm, K = 0.24, and t0 = -1.70. The curves indicate an average size of an individual of a given species at a certain age. They also give an estimation of a maximum length (L) of each species, in addition to specific growth rate, which is indicated by the slope. Parameters of each resulting Von Bertalanffy equation were compared among species. Results were also compared with growth rates currently used in stock assessments by fisheries management organizations, such as the International Commission for the Conservation of Atlantic Tunas (ICCAT).

Comments

Project funded by Nova Southeastern University through the FY13 Presidents Faculty Research and Development Grant.

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