Age and growth of the great hammerhead shark, Sphyrna mokarran, in the north-western Atlantic Ocean and Gulf of Mexico
Andrew N. Piercy A , John K. Carlson B C and Michelle S. Passerotti BA Florida Program for Shark Research, Florida Museum of Natural History, University of Florida, PO Box 117800, Gainesville, FL 32611, USA.
B NOAA/National Marine Fisheries Service, Southeast Fisheries Science Center, 3500 Delwood Beach Road, Panama City, FL 32408, USA.
C Corresponding author. Email: john.carlson@noaa.gov
Marine and Freshwater Research 61(9) 992-998 https://doi.org/10.1071/MF09227
Submitted: 9 September 2009 Accepted: 10 February 2010 Published: 23 September 2010
Abstract
The great hammerhead shark, Sphyrna mokarran, is a cosmopolitan species that is caught in a variety of fisheries throughout much of its range. The apparent decline of great hammerhead shark populations has reinforced the need for accurate biological data to enhance fishery management plans. To this end, age and growth estimates for the great hammerhead were determined from sharks (n = 216) ranging in size from 54- to 315-cm fork length (FL), captured in the Gulf of Mexico and north-western Atlantic Ocean. Growth curves were fitted using multiple models and evaluated using Akaike’s information criterion. The von Bertalanffy growth model was the best fitting model, with resulting growth parameters of L∞ = 264.2-cm FL, k = 0.16 year–1, t0 = –1.99 year for males, and L∞ = 307.8-cm FL, k = 0.11 year–1, t0 = –2.86 year for females. Annual band pair deposition was confirmed through marginal-increment analysis and a concurrent bomb radiocarbon validation study. Great hammerheads have one of the oldest reported ages for any elasmobranch (44 years) but grow at relatively similar rates (on the basis of von Bertalanffy k value) to other large hammerhead species from this region. The present study is the first to provide vertebral ages for great hammerheads.
Additional keyword: von Bertalanffy.
Acknowledgements
We thank NOAA Fisheries observers and Florida Program for Shark Research scientists for assistance with collection of shark specimens for this study. We extend our gratitude to the numerous student interns and volunteers for helping with the preparation of vertebrae. We thank two anonymous reviewers who provided valuable comments on this manuscript. A portion of the funding for this project was contributed by the National Marine Fisheries Service’s Highly Migratory Species Division through the Florida Program for Shark Research, a member institution in the National Shark Research Consortium.
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