Estimates of life history parameters of the oceanic whitetip shark, Carcharhinus longimanus, in the Western North Pacific Ocean

Abstract

The age, growth and reproduction of the oceanic whitetip shark, Carcharhinus longimanus, in the western North Pacific Ocean were estimated based on 188 specimens (89 females and 99 males) collected before the prohibition of retaining on board for commercial use by the Western and Central Pacific Fisheries Commission (from November 2002 to January 2006) at the Nanfanao fish market in north-eastern Taiwan. The relationship between body weight (W) and total length (TL) for both sexes combined was estimated as follows: W = 1.66 x 10(-5)TL(2.891) (n = 188, P < 0.01). The relationship between TL and the pre-caudal vertebral centrum radius (R) for sexes-combined data was described using the following equation: TL = 29.98 + 20.99R (n = 112, P < 0.05). The opaque bands in pre-caudal vertebrae are formed once annually between June and September based on a marginal increment ratio analysis. The maximum number of growth band pairs was 12 for both sexes in this study. The two-parameter von Bertalanffy growth function best fits the length-at-age data, and the growth parameters (sexes combined) were estimated as follows: asymptotic length (L-infinity) = 309.4 cm TL and growth coefficient (k) = 0.085/yr with the size at birth set as 64 cm TL (n = 112, P < 0.01). The litter size was 10-11, and the size at birth was at least 64 cm TL. The sizes at first and 50% maturity were 190 cm and 193.4 +/- 0.97 cm TL for females and 172 cm and 194.4 +/- 6.57 cm TL for males. These corresponded to 8.5 yr and 8.8 yr for females and 6.8 yr and 8.9 yr for males.