Patterns of reproduction and spawning of the kingfish (Scomberomorus commerson, Lacépède) in the coastal waters of the Sultanate of Oman

Patterns of reproduction and spawning were determined for the kingfish (Scomberomorus commerson, Lacépède) in two oceanographic regions of the Sultanate of Oman. During 2 years of sampling, 1264 fish were purchased from fishermen at landing sites along the Arabian Sea and the Gulf of Oman. Sizes of males and females were similar in both regions but more females were caught along the Gulf of Oman than along the Arabian Sea coast. Females matured at a significantly smaller length and about 2 months earlier than males in both regions. For both sexes, the fish collected along the Arabian Sea matured approximately 10 cm smaller and 6 months earlier that those of the Gulf of Oman. Analysis of the reproductive stages and gonosomatic index revealed a single yearly reproductive cycle beginning in February and ending with a single spawning period in May-June, just prior to the onset of the summer oceanographic regime. Reproductive stages and growth also indicated that 40% of the landings along the Arabian Sea is composed of fish before their first reproduction (Stage I) whereas along the Gulf of Oman, only 25% of the fish were caught before entering active reproduction. Several indicators suggest that kingfish stocks are under intense pressure and that management of this species should be implemented rapidly if they are to remain sustainable.