34 June 2012 Spawning and larval rearing of goldlined seabream, Rhabdosargus sarba on Abu Al Abyad Island, United Arab Emirates Omer M. Yousif1, Kumar M. Krishna, Bui V. Hung, A-Fatah A. Ali and Do V. Minh The goldlined seabream, Rhabdosargus sarba, a carnivorous and euryhaline sparid, is widely distributed in subtropical and tropical waters throughout the Indo-West Pacific including the Red Sea, East Africa, Madagascar, Australia, China and Japan (Leu 1994, Mihelakakis and Kitajima 1995, Radebe et al. 2002). It is a shallow-water species that is usually found around reefs with sandy bottoms. In some regions of the world, such as the waters of Hong Kong and South Africa, the fish is a protandrous hermaphrodite, but in other environments, including Western Australia, it is described as a rudimentary hermaphrodite (Hesp et al. 2004). In the United Arab Emirates (UAE), the fish is a potential candidate for aquaculture because it has high commercial value in the local market. In the wild, R. sarba spawns from early December to late January, when water temperature is around 21 °C. We studied the spawning and larviculture of goldlined seabream. Broodstock Acquisition and Spawning Broodstock were captured from channels surrounding Abu Al Abyad Island during early December 2009 and transported to the Aquaculture Center where they were immediately given a 0.15 ppm formalin (42 percent) bath for one hour, and then placed in 4-m3 indoor fiberglass tanks filled with seawater (51 ppt). Two days later, fish were acclimatized to hatchery conditions by reducing salinity to 37 ppt over two days. After seven days, fish were weighed, measured and cannulated with a 2-mm polyethylene cannula. Females were 270 ± 18 g and 23.1 ± 0.6 cm in length, while males averaged 265 ± 16 g and 23.4 ± 0.9 cm. During the acclimation period and all through the spawning period, broodstock were fed fresh squid and sardines daily to satiation, supplemented with clam meat three times per week. Every other day the fresh food was fortified with vitamins and oil. On 12 December 2009, ripe females with average cannulated oocyte diameter of 406 µm and ripe males with running milt were randomly distributed into three identical 40m3 indoor circular concrete tanks at 25 females and 25 males in each tank. Fish in one tank (group A) were given a priming injection of 1000 IU HCG/kg body weight followed 24 hours later by a resolving dose of 200 µg LH-RHa/kg body weight. Fish in a second tank (group B) were given only one Fig. 1. Female Rhabdosargus sarba cannulation. dose of 1000 IU HCG/kg body weight while fish in the third tank (group C) were not injected and left to spawn naturally. In group A, spawning occurred 24 hours after the second injection, with a total release of 3,710,000 eggs. The fertilization rate in this group was 71 percent. In the second group (group B), spawning occurred 48 hours after receiving the only HCG injection with a total release of 3,410,000 eggs released. The fertilization rate in this group was 66 percent. Fish in group C failed to spawn naturally within 36 days from 12 December 2009 to 17 January 2010. It is probable that handling stress of wild fish during the short period of time from acquisition to introduction for spawning inhibited the development and final maturation of gonads in group C fish. Every morning, buoyant eggs with a diameter of 920 ± 1 µm were skimmed from the water surface of the spawning tanks using a fine dip mesh net (100-µm mesh size). Immediately after egg collection spawning tank bottoms were siphoned to remove sinking eggs and 50 percent of the tank water was changed. Collected eggs were rinsed with filtered seawater, separated and counted using a graduated cylinder and transferred into 600 µm cylindrical incubation baskets. Incubators were placed in a 5-m3 rectangular fiberglass tank that was provided with gentle aeration and continuous gen-
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