Age and Growth of the Blue Shark (Prionace glauca) in the South Atlantic Ocean

The blue shark Prionace glauca, an oceanic migratory elasmobranchii species, was one of the most commonly bycatch species caught by long-liners. A total of 337 male, 311 female, and 137 sex unknown blue sharks caught by Taiwanese far sea long-line vessels in the South Atlantic (50̊ 35́W-13̊ 51́E, 40̊ 6́S-0̊ 57́S) between December 2006 and December 2011 were collected for age and growth analysis. The vertebrae from caudal peduncle region sampled by observers were used for aging. Growth band pairs were read via images photographed from X-ray films. Marginal increment ratio and centrum edge analysis indicated that the growth band pair (including translucent and opaque bands) on vertebral central was formed once a year. The Akaike’s information criterion indicated that the von Bertalanffy growth function (VBGF) best fit the observed total length (TL) at age data. The VBGFs were not significantly different between sexes using likelihood ratio test (P > 0.05).Growth parameters were estimated to be L∞ = 352.1 cm TL, k = 0.13 yr-1, and t0 = -1.31 yrs for sex combined blue shark. The longevity was estimated to be 21.4 years at least.