Estudo da biologia do tubarão-galha-preta ( Carcharhinus limbatus, Muller & Henle 1939), desembarcado no centro de pesca de Zalala, província da Zambézia

Abstract

The Blacktip Shark (Carcharhinus limbatus) is a common coastal species that inhabits tropical and subtropical waters around the world. This study was based on historical data from the artisanal fishing sampling system of the National Institute for Fishery Research (IIP). The objective of this work was to study the biological aspects of the species, namely, the reproductive cycle of females and the growth pattern of Carcharhinus limbatus, as well as to analyze the population structure in the landings. The survey was based on a monthly sampling in the fishing center of Zalala, Zambezia Province, from October 2017 to September 2018, where they were weighed (kg) and measured (cm) individually. The individuals were identified by sex and the female reproductive cycle was analyzed based on the morphology of the testes and ovaries and the growth parameters were estimated by the ELEFAN I method, inserted in the FAO-ICLARM Fish Stock Assessment Tools computational package. Of the 562 individuals analyzed, 186 (33.1%) were male, with length ranging from 12.5 to 191cm and 376 (66.9%) female, with length ranging from 12 to 211cm. The sex ratio was 2:1 (female: male), which differed significantly (p <0.05) from expected (1: 1). Growth of C. limbatus was negative allometric for both sexes, maturation of C. limbatus was not continuous throughout the sampled period, where females reach sexual maturity at 99.29 cm in length. The von Bertalanffy growth equation for growth in length is Lt = 125 [1- e -0,103 (t – 1, 42)] for females that were shown to grow faster than males with the equation Lt= 105 [1- e-0,101 (t -0,123)]. In the description of the statistical analyzes, it was found that males had a higher number of juveniles than females, showing the peak in May and June. However it is concluded that recruitment is continuous.