Abstract
The reproductive biology and fishery-related characteristics of the Malabar grouper (Epinephelus malabaricus) (Bloch and Schneider, 1801) specimens were investigated. The size of females ranged from 25 to 113 cm total length (LT), with 50% sexually mature at 79 cmLT, and the males (97 cm to 114 cmLT) were larger than the females. Due to the sex ratios and size distribution of the sample, it appeared that the groupers change sex between 97 and 113 cmLT. However, the gonadal histology data lacked specimens in the transitional stage. The spawning peak occurred in November, as defined by the presence of ripe females, and the spawning season lasted from September to February. The size of the fish correlated positively with the water depth at capture, which is also related to oxygen levels in deep water being more favourable for larger fish. Larger specimens (>100 cmLT) were targeted by fishers between December and February, when the northeast monsoon coincides with calmer weather and the spawning season. Fishers were interviewed, and observations were made on fishing gear, vessels, and grounds. There was no indication that small-scale fishers targeted spawning aggregations; therefore, fisheries independent research is recommended in order to verify the time, location, and behaviour of the spawning of Malabar groupers for management and conservation purposes.
Highlights
The population size structure, mode of reproduction, maturity, and fisheries characteristics of various Epinephelinae are well documented in the Western Atlantic, the Caribbean, Southeast Asia, and Australian waters [1,2,3,4]
This study aims to determine the reproductive biology and fishery-related characteristics of Epinephelus malabaricus caught by small-scale fishers in the inshore waters of Mafia Island, Tanzania
The results show that the Epinephelus malabaricus from around Mafia Island displays isometric growth (i.e., b = 3.08) similar to estimates reported by Kulbicki et al [35]
Summary
The population size structure, mode of reproduction, maturity, and fisheries characteristics (fishing gear, vessels, and fishing grounds) of various Epinephelinae are well documented in the Western Atlantic, the Caribbean, Southeast Asia, and Australian waters [1,2,3,4]. The Epinephelinae are heavily exploited in many tropical areas of the world for commercial purposes, aquaculture ventures (e.g., Epinephelus malabaricus and Epinephelus coioides) and for recreational and local consumption [4,5,6]. A few species, such as the Epinephelus coioides and the Epinephelus andersoni, are diandry, where the males can either develop from the females or they can develop directly from the juvenile phase [10,11,12]. The latter sexual pattern suggests that some females do not change sex at all, and some males do not pass through female stages at all
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