The overall objective was to develop improved hatchery and grow-out technology as a basis for increasing production of grouper reef fish in the Asia-Pacific region.
The large and increasingly affluent market for live reef fish such as grouper, particularly in Hong Kong and southern China, has increased pressure on stock in the wild. In many areas the demand for live reef fish, and the large profits to be made by their supply, has encouraged over-fishing and the use of destructive and environmentally damaging practices to acquire the fish. This includes putting sodium cyanide in the sea to immobilise the fish so that they can be caught easily by divers. Many fish, and presumably other organisms, are killed in the process and the reefs are devastated.
Much of this can be avoided by growing desirable reef fish in aquaculture. Grouper aquaculture has the potential to provide fish for the Asian market and become an important income earner in coastal regions in Indonesia. The main barrier however is the extremely low survival rates of most species raised from the larval stage, in many cases averaging less than 5%. As a result many aquaculture enterprises seek to capture juvenile fish and raise these to market-ready stage, placing considerable pressure on wild fish resources.
The main problem restricting aquaculture for groupers is their very variable, and often rather poor, survival when in the larval stage. Another difficulty is the supply of fish for feed - referred to as ‘trash’ fish. These low-value fish, which could be used for human consumption in low-income countries, are increasingly being put into aquaculture feeds for high-value fish. In some areas their supply is dwindling.
Recent international workshops identified areas where research was needed to develop commercially viable aquaculture for groupers. This project carried out research in several critical areas and helped to develop a collaborative network of grouper aquaculture researchers in the region.
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This period covered by Final Report - see Final Report.
Optimising environmental variables of temperature, salinity, aeration, and light levels provided valuable information contributing to greater larval survival.
Larval nutrition research indicated the essential fatty acid requirements of one species of grouper (Epinephelus coioides). Further work will be aimed at developing larval diets to provide suitable levels of various fatty acids the larvae require.
Research described the development of the digestive tract in larval groupers. This is fundamental to knowing the capacity of the larvae to digest both live and artificial feeds.
Highly sensitive fluorescent techniques were developed to assess the levels of digestive enzymes in the gut of fish larvae. Grouper larvae were shown to have very low levels of digestive enzymes (e.g. protease) compared with some other species of fish larvae that have been examined, such as barramundi. This may help explain why grouper larvae are more difficult to rear than barramundi.
Assessment of techniques to maintain or decrease the size of super-small (SS) strain rotifers (Brachionus rotundiformis) for use in grouper hatcheries. Improved intensive and semi-intensive larval rearing techniques resulted in survival rates increasing from around 3% at the beginning of the project to 30% for greasy grouper / estuary cod (E. coioides), and from 5% at the beginning of the project up to 50% for humpback grouper / barramundi cod (Cromileptes altivelis).
The viral disease viral nervous necrosis (VNN) continues to cause major mortalities in hatchery-reared grouper and remains a major limiting factor in successful seed production. Technology developed under the project has been adopted by farmers, including ‘backyard hatcheries’ in Bali. A socio-economic analysis of these small-scale hatcheries demonstrated that they are highly profitable, with payback periods generally <1 year and IRRs of 12-356%.
Grow-out diet development
Protein of Australian meat and bone meal and wheat gluten and local and imported fishmeal was found to be well digested (Apparent Digestibility (AD) >76%). The protein digestibility of Australian blood meal was variable but generally low as also was the digestibility of rice bran. Intermediate in protein digestibility were local ingredients such as shrimp head meal, palm oil cake meal and soybean meal.
Research with humpback grouper / barramundi cod (C. altivelis) showed that diets had to be high (> 55%) in protein and moderate (12-15%) in lipid to optimise growth rate and nutrient retention in the fish. Increasing the amount of lipid in the diet only increased fat deposition without any improvement in growth or food conversion efficiency. These findings need to be confirmed with other grouper species.
Other research showed that many terrestrial protein meals have potential as partial replacements for fishmeal in grouper grow-out diets. Good quality meat and bone meal can replace more than two-thirds of the fishmeal without any adverse effect on grouper performance. Plant protein meals such as soybean and lupin have been shown capable of successfully replacing from one-third to half of the fishmeal.
Researchers in Indonesia have categorised (cost, seasonal availability, composition, digestibility) a range of potential ingredients for use in locally-made grouper diets.
Commercial feed producers in Indonesia and the Philippines are now trialing grouper diets based on the outcomes of the project’s research.