Reproductive biology of the Blue shark (Prionace glauca) in the western Indian Ocean

Citation
Murua H, Artetxe-Arrate I, Farley J, et al (2021) Reproductive biology of the Blue shark (Prionace glauca) in the western Indian Ocean. In: IOTC- 17th Working Party on Ecosystems & Bycatch (Assessment). IOTC-2021-WPEB17(AS)-11, Online, p 9
Abstract

This paper describes preliminary work to assess the sex-ratio and the length at 50% maturity of blue shark in the southwest Indian Ocean as part of the ‘GERUNDIO’ project . A total of 266 samples were collected and for 206 individuals the macroscopic maturity staging was reported as part of the project. The maturity staging was observed from sharks ranging in size from 53 to 275 cm straight fork length (SFL) for males and between 105 and 254 cm SFL for females and all sharks were caught in the southwest Indian Ocean off the coast of South Africa. According to available data, males individuals were much more numerous, especially in large individuals. Estimated size at 50% maturity was 201.7 cm SFL for males, 142.0 cm SFL for females and 190.5 cm SFL for both sexes combined. The maturity ogive estimated in our study is similar to the size at 50 % maturity used for blue shark stock assessment in the Indian Ocean, which uses a knife edge logistic maturity schedule with the length-at-50% maturity for females equal to 145cm.