Aspects of the reproductive biology of the data-deficient Mustelus minicanis and M. norrisi (Chondrichthyes: Triakidae) in the southern Caribbean Sea

Abstract

Reproduction and maturation in the economically important, but data-deficient, Mustelus minicanis and M. norrisi were analysed using catches of populations exploited by a gillnet fishery during two years in the southern Caribbean Sea. In total, 691 female (mean ± SD total length–TL of 55.3 ± 5.8 cm) and 503 male (50.4 ± 4.9 cm TL) M. minicanis were assessed, with ~95% of all specimens deemed mature. Almost 25% of females were gravid (occurring between January and October) and with variable temporal development of up to six embryos (3.3 ± 1.2), implying protracted temporal parturition. Parity in the sex ratio of embryos, but not in landed catches, suggested sexual segregation across the fished area. The 50% sizes at maturity (M 50) (± SE) were similarly estimated at 45.11 (± 0.39) and 45.48 (± 0.42) cm TL for females and males, respectively. Relatively fewer (235) M. norrisi were landed, with samples comprising 150 females (82.6 ± 18.1 cm TL) and 85 males (75.5 ± 17.7 cm TL). More than 30% of both sexes were immature. Ten percent of females were gravid (up to 11 embryos) and present in catches between October and February, coinciding with the northern hemisphere autumn/winter. Female and male M 50s were 76.65 (± 1.16) and 69.63 (± 1.92) cm TL, respectively. The results imply variable inter-specific reproductive plasticity and the need for further life-history studies. Increasing gillnet selectivity might represent a simple precautionary management option for concurrently regulating catches of the smaller-bodied M. minicanis during peak abundances of gravid females and similar-sized juvenile M. norrisi.