Isnin, 13 April 2009

Selasa, 31 Mac 2009

Breeding the giant grouper and improving broodstock

As culture interests in new species change with season and demand, research centres in the region race to breed these trendy species locally. In Malaysia’s Marine Fish Production and Research Centre (MAFPREC) the focus is now on breeding the giant grouper Epinephelus lanceolatus and also brood stock development of core species such as the Asian sea bass Lates calcarifer.
It has been the trend with marine fish farmers to change species with season, prices and availability of fingerlings. Breeding and larval rearing technology had to keep up with these fast changing demands. Hussin Mat Ali, the Head of the centre located in Tanjong Demong, Besut, Terengganu on the East Coast of Peninsula Malaysia said, “When we started, our mission was production for the farmers in line with our motto ‘Fish Farmers First” and so we had to keep up with the changing preferences of industry. We also had to keep up with progress in the hatcheries and research institutes in Taiwan and Indonesia, leaders in marine fish fry production. Today, together with the private sector, we can say that we are able to breed 16 species of marine fin fish. Now we need to move on to refining technologies such as improving spawning output of the giant and tiger groupers, brood stock improvements and in improving recirculation aquaculture systems for larval rearing”. The centre was initially established as a production centre for marine fish and shrimp fry production. It started with larval rearing of sea bass with eggs spawned at the Fisheries Research Institute in
Penang in 1983 and went on to complete the cycle for the sea bass in 1985. In 1992, it was upgraded to a research centre. The series of success have been with the following species; green grouper E. coioides (1990), snapper Lutjanus johnii (1990), red snapper L. argentimaculatus (1993), tiger grouper E. fuscoguttatus (1995), pompano Trachinotus blochii (1998), red snapper L. erythropterus (1998), and red drum Sciaenops ocellatus (2000). Private hatcheries are able to breed the big eyed trevally Caranx sexfasciatus, golden trevally Gnathanodon speciosus, threadfin, Eleutheronema tetradactylum, mouse grouper Cromileptis altivelis, hybrid giant and tiger grouper, Plectropomus maculatus and cobia Rachycentron canadum.
Breeding the tiger and giant grouper
Currently, breeding technology is centred on the popular tiger grouper and MAFPREC holds the brood stock in cement tanks. Three pairs are used for spawning via hormonal stimulation each month to produce 5 to 10 million eggs per spawning. Brood stock is replaced every 3-4 years with wild stocks. Eggs are supplied free to private hatcheries such as former marine shrimp hatcheries for larval rearing and nursery to 2.5cm and 10cm fingerlings in 90-100 days. The hatcheries sell these at MYR 1 per 2.5cm.
The giant grouper is the next popular species. The centre holds 95 broodstock of which only 15-20 are ready to spawn. Fish are fed juvenile tuna and water is exchanged every two days in the 150 tonne cement tanks. At more than 30 kg there are apparent signs of maturity but cannulation only indicates ready to spawn males in more than 50 kg fish. Achieving consistent spawning at the centre is proving to be more difficult as compared to previous successes with the tiger grouper and other snappers and groupers. Similar to the green grouper, usually only 10% of the mature fish are males but the challenge is how to obtainthe right balance of males to females. Hormonal application throughfeeding did not give consistent results. The centre is looking at novel application techniques in hormonal sex reversal to have more malesto work with.