SPAWNING, LARVAL REARING AND GROWTH OF THE SILVER SILLAGO, Sillago sihama (Forsskal 1775) IN THE UNITED ARAB EMIRATES
Sillago sihama, silver sillago (locally known as Hasoom), a highly esteemed fish, was first spawned in the United Arab Emirates at the Aquaculture and Marine Studies Center (AMSC), Abu Al Abyad Island. A total of 204 S. sihama breeders with an average length of 15.07 cm and average weight of 25.30 g were collected from Al Hanyoura area, northeast of Abu Dhabi during December 2012 and brought to the AMSC where the fish were stocked in a 40-t circular tank in 45 ppt seawater. The fish were fed on a diet of squid, sardines, shrimps and pelleted feed (52% CP).
Natural spawning was observed for the first time in January 2013. Subsequent to the first spawn four more spawns were obtained until the end of February 2013. The total number of eggs yielded was 192,000 small spherical floating eggs averaging 714 μm in diameter out of which 94% were good eggs. The good eggs were kept for incubation at 45 ppt and 22.0-23.0 ºC. The eggs hatched out within 26 hrs and the hatching rate was 56%. The newly hatched larvae, measuring 1.64±0.16 mm, were transferred to 4-t tanks at 25 larvae/l and were fed with 60 μm rotifers, copepod nauplii, artemia nauplii and artificial feed for 40 days. The overall larval survival was only 1.03%. This low survival rate was attributed to the initial mortalities during the first week which was probably due to lack of proper prey size for the larvae to feed upon. Also, in the 9th week post hatch the larvae were infected with the protozoan parasite Cryptocaryon irritans causing an additional mortalities.
After weaning, the fish were further grown for 32 weeks and were fed with 0.3-0.9, 2 mm feed and fresh whole sardines placed at the bottom of the nursing tanks. At harvest the fish average body length was 13.6 cm and the average body weight was 12.80 g.