Age and growth of the whiskery shark, Furgaleus macki, from southwestern Australia

Abstract

Age and growth of the whiskery shark, Furgaleus macki, from southwestern Australia were examined using vertebral ageing and tag-recapture data. The readability of bands on the vertebral centra varied markedly between individuals. Four readers were used to make band counts, with the most experienced reader having the lowest 'index of average percent error' and the highest level of agreement with final counts. Marginal increment analysis indicated that opaque bands form in January. With parturition occurring from August to October, size data suggests that the first band is probably formed 15-17 months after birth. The age at maturity was estimated to be 4.5 years for males, and 6.5 years for females. The oldest male was 10.5 years, and oldest female was 11.5 years. Von Bertalanffy growth parameters for males were L(∞) = 121.5 cm fork length, K = 0.423 year-1, to = -0.472 years, were L(∞) = 120.7 cm fork length, K = 0.369 year-1, to = -0.544 years for females, and were L(∞) = 118.1 cm fork length, K = 0.420 year-1, to = -0.491 years for combined sexes. Data from a tag recapture study were analysed using a maximum likelihood method to verify the estimates of growth parameters from vertebral ageing. Von Bertalanffy growth parameters from the tag recapture study were L(∞) = 128.2 cm fork length, K = 0.288 year-1, to = -0.654 years. The two methods of estimating growth parameters produced similar results, with rapid growth until approximately 5 years of age, after which there was little increase in length.