Age, growth and reproductive biology of the blue shark Prionace glauca in South African waters

Abstract

The age, growth and reproductive biology of the blue shark Prionace glauca from South African waters were assessed using 205 specimens, ranging in total length (TL) from 72 to 313 cm. Greater number of males (120) than females (85) were examined as they were more frequently caught. Age and growth parameters were estimated using a von Bertalanffy growth model; estimates for the sexes combined were L _∞ = 311.6 cm, k = 0.12 y⁻¹ and t ₀ = −1.66 y. Sex-specific growth curves were not significantly different (F-statistic = 1.59, df = 3 197, p > 0.05). Growth estimates from our study fall within the reported ranges and confidence intervals for other studies on blue sharks. Phi prime (φ′) values showed little variation in the growth of the blue shark across its geographic range. Length- and age-at-50% maturity were estimated at 201.4 cm TL and 7 years for males and 194.4 cm TL and 6 years for females. Only one pregnant female was examined, which had 43 embryos, and another that had recently given birth had 55 uterine scars.

Keywords:

• growth estimates
• maturity
• phi prime
• South Atlantic