As noted earlier, wild-caught groupers still make up the bulk of the seedstock supply in many parts of Southeast Asia, including Vietnam, Thailand and the Philippines.
The trade in wild fry is associated with a number of resource management issues including overfishing, use of unsustainable harvesting techniques (including cyanide), high levels of mortality, and inadequate supply to support the demand of a developing aquaculture industry (Sadovy 2000).
To meet aquaculture’s demand for seedstock and to reduce pressure on wild fisheries, there is a recognised need to develop commercial marine finfish hatcheries throughout the Asia-Pacific region to supply hatchery-reared seedstock.
At the beginning of this project, despite at least a decade of research, hatchery production of groupers remained a limiting factor in grouper aquaculture. Average survival to fingerling stage (about 25 mm in length) was low, generally in the range 0–10% (Rimmer 1997, 1998, Rimmer et al. 2000).
In addition, survival was highly irregular — one or two larval rearing ‘runs’ often resulted in reasonable (up to 10%) survival, while others had zero survival. Both of these factors (low average survival and unreliable hatchery production) were major constraints to the commercialisation of grouper larviculture technology.
In 1997 Taiwan was the only commercial producer of grouper fingerlings in the Asia- Pacific region (Rimmer 1998; Rimmer et al. 2000; Liao et al. 2001). Production of grouper fingerlings in Taiwan is largely limited to Epinephelus coioides and E. malabaricus , although there has been experimental production of several other species, including E. lanceolatus , Plectropomus spp. and Cromileptes altivelis (Rimmer 1998; Liao et al. 2001).
Larval rearing of groupers in Taiwan remains problematic, and many (wild caught) fingerlings are imported from other parts of Asia, particularly Thailand (Ruangpanit 1993; Sadovy 2000). Overall survival estimates are not available, but in 1997 Taiwanese farmers regarded the equivalent of 7% survival to 2.5–3 cm in length as excellent (Rimmer 1998).
The larval rearing component of the ACIAR project concentrated on a relatively broad range of research topics to assess which areas were likely to be limiting factors in successful grouper larviculture. These were:
- Environmental requirements to optimise survival in pre–feeding larvae.
- Nutritional (particularly fatty acid) requirements of larval groupers.
- Isolating and culturing SS–strain rotifers for use in grouper larviculture.
- Assessing the capacity of larval groupers to digest live and artificial prey, including documenting the development of the digestive tract and the ontogeny of digestive enzymes.
- Defining hatchery management techniques for larval rearing of groupers.
Cromileptes altivelis is found through the Western Pacific from southern Japan to Palau, Guam, New Caledonia, and southern Queensland (Australia); and in the eastern Indian Ocean from the Nicobars to Broome, Western Australia. It is a high-value species in the live reef fish trade, bringing up to US$70 per kg wholesale.
Juvenile fish are in demand as aquarium inhabitants. Commonly known as humpback grouper or polkadot grouper, it is known as barramundi cod in Australia, kerapu tikus or kerapu bebek in Indonesia, and señorita in the Philippines.
Research results were continually integrated into hatchery verification trials to assess the practical outcomes of the research. The results of the larval rearing component are detailed in Section 2 of this publication.
Author:
M.A. Rimmer
