Journal
MARINE BIOLOGY RESEARCH
Volume 13, Issue 3, Pages 300-313Publisher
TAYLOR & FRANCIS AS
DOI: 10.1080/17451000.2016.1267366
Keywords
Age and growth; smooth hammerhead; Atlantic Ocean; vertebral band counts; back-calculation; life history
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Funding
- Portuguese Foundation for Science and Technology (FCT), Fundacao para a Ciencia e a Tecnologia [SFRH/BD/60624/2009]
- EU European Social Fund
- Programa Operacional Potencial Humano [IF/00253/2014]
- Fundação para a Ciência e a Tecnologia [SFRH/BD/60624/2009] Funding Source: FCT
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The smooth hammerhead Sphyrna zygaena (Sphyrnidae) is a pelagic shark occasionally caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Age and growth of S. zygaena was studied along a wide Atlantic region covering both the northern and southern hemispheres. Data from 304 specimens, caught between October 2009 and September 2014, ranging in size from 126 to 253 cm fork length (FL), were analysed. Growth models were fitted using the three-parameter von Bertalanffy growth function (VBGF) re-parameterized to calculate L-0 (size at birth). Growth models were fitted to the sample data and data from several back-calculation models. The model fit to the quadratic modified Dahl-Lea back-calculated data seems to be the most appropriate to describe growth in this species, with resulting growth parameters of L-inf = 285 cm FL, k = 0.09 year(-1) for males and Linf = 293 cm FL, k = 0.09 year(-1) for females. Compared with other species of the same genus, estimated growth coefficients for S. zygaena seem to fall in the low to middle range. Although further work is still needed, this study adds to knowledge of the vital life-history parameters of smooth hammerheads in the Atlantic Ocean, which can be used in the management and conservation of this species.
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