Reproductive biology of the mackerel scad, Decapterus macarellus (Cuvier, 1833), in the Sulawesi Sea, Indonesia

Indonesia is the second largest fishery producer in the world, producing many small pelagic fish. To improve information for sustainable fishery management in the Sulawesi Sea, we examined the reproductive biology of the main target species, the mackerel scad Decapterus macarellus (Cuvier, 1833). Between May 2020 and March 2021, we collected 1267 mackerel scads from two landing sites in northern Sulawesi. These fish ranged from 13.4 to 38.2 cm in total length, and their sex ratio, length at first maturity (Lm), reproductive periodicity, and potential spawning grounds were studied. An equal male to female (M:F) sex ratio of 0.98:1.00 was osberved. The lengths of males and females at first maturity (Lm) were 22.59 and 21.62 cm, respectively. The mackerel scads spawned throughout the year, peaking in January, March, May, and September. Spawning occurs mainly during the first quarter of the moon's phase. Most mature individuals with a high gonadosomatic index were found near Tumumpa Dua and the northern and western coasts of the Sangihe and Siau Islands, suggesting that there are specific locations where mackerel scads spawn. Fishery managers can use this information to implement temporary and regional fishing closures to develop sustainable fishing practices for small pelagic fish species.