aquaculture

T. Petr and D.B. Swar have edited and published, at the FAO, a report (2002) entitled Cold Water Fisheries in the Trans-Himalayan Countries. The abstract:

The trans-Himalayan region encompasses a number of countries situated in the midland and highland areas of the Himalayas, Karakoram and, in a broad sense also, in Hindu Kush and Pamir. The mountains are characterized by a very low level of human development, with full exploitation or overexploitation of the natural resources. Fisheries play an important role in providing food and income to the mountain people. The Symposium on Cold Water Fishes of the Trans-Himalayan Region, held from 10 to 13 July 2001 in Kathmandu, Nepal, was attended by 70 participants from 10 countries. Comprising 32 presentations, the symposium reviewed information, experiences, ideas and findings related to fish and fisheries in the region. Special attention was given to fish species distribution, fishing intensity, socio-economic conditions and livelihoods of fisher communities, as well as to the impacts of environment degradation, conservation measures and aquaculture technologies on indigenous and exotic cold water fish. The symposium highlighted the role of fisheries in providing food and income to people within the trans-Himalayas and Karakoram. Recognizing the need to increase the role of aquatic resources in poverty alleviation, the symposium urged national governments to give greater attention to fisheries development in mountain areas. A number of priority issues were indentified, including collaborative action on a regional scale, which would probably be the most cost-effective way to address these common problems and to share experiences. The recommendations are expected to be addressed in follow-up activities under a trans-Himalayan regional programme.

Contained in the document is a report on research conducted into the domestication of wild golden mahseer (Tor putitora) and hatchery operations leading to the expansion of aquaculture of the species.

The mahseer is a robust species, amongst the largest of the world’s freshwater scaled fish. Six different species have been recognised under the genus, each of which inhabit very different environs. Some are indigenous to tropical waters with a high of 35°C, while others have adapted to sub-Himalayan regions where temperatures dip to 6°C in winter. The golden mahseer, capable of growing to a maximum of 2.75 metres in length and topping 200lb in weight, remains the king of its class.

From the abstract:

Golden mahseer (Tor putitora) are found in most of the south Asian countries including Nepal, India, Bangladesh, Pakistan, Afganistan, Sri Lanka, Myanmar. This popular game fish attains over 50 kg (Thapa, 1994). The population of this fish has been declining because of overfishing, also using destructive fishing methods such as electrofishing and poisoning, and because of the degradation of aquatic environment. India has already identified this fish as endangered (Shrestha, 1988a). Nepal and some other countries are in a stage of enlisting the fish as an endangered species. Strict application of the Aquatic Act and regular restocking of natural water bodies with appropriately sized mahseer can revive their stocks. A joint effort of restocking this migratory fish in the respective water bodies in the region can help to restore their stocks, and all countries should join a programme to revive the fish stocks in the lakes and rivers of their own. Nepal, India and Bangladesh have been attempting to develop large scale seed production technology of mahseer. Information on breeding of golden mahseer is readily available (Tripathi et al., 1977; Pathani and Das, 1979; Masuda and Banstola, 1984; Joshi, 1984; Shrestha 1987, 1988; Shrestha et al., 1990; Sehgal, 1991), but information on domestication of wild broodstock and its hatchery production is scanty (Ogale, this volume). The old practice has been to rear the wild mahseer in captivity. Brood fish grown in captivity can produce the required quantity of seed. Masuda and Banstola (1980) did not foresee the possibility of growing the wild breeders to sexual maturity in captivity. Shrestha (1990) believes that mahseer do not breed in stagnant reservoirs where water circulation is poor. However, the wild breeders grown in earthen ponds, not supplied with running water, attain sexual maturity and exhibit sexual play with the male chasing the female making a loop during the spawning time. The fish spawn twice a year. Its first spawning in April/May is followed by the second one in August/September. Males grown in captivity but it is difficult to sort out females just ready to spawn. This study describes the hatchery operation of wild golden mahseer reared in an earthen pond.

Jiansan Jia and Jiaxin Chen, have published a paper (2001) entitled Sea Farming and Sea Ranching in China.

The abstract:

The various sea farming and sea ranching practices used in the People’s Republic of China are reviewed, based on published and unpublished information, statistical data and field experiences. The development of marine fisheries during the past 50 years is described. Following their decline caused by overfishing and the ecological degradation of the coastal environment, emphasis was shifted from marine capture fisheries to aquaculture-based operations, including farming and ranching of marine organisms both in inshore and offshore areas. The biology and culture of major representatives of five species groups (seaweed, molluscs, crustaceans, echinoderms and fish), involving a total of 67 different species, are presented, together with detailed production statistics. The eight sea farming and ranching systems actually used in China are presented. Several aspects related to marine resources management for sea farming and ranching are discussed, such as legislation, research on genetics and biodiversity, health management and marine habitat rehabilitation. Monitoring and evaluation according to biological, environmental and socio-economic standards are briefly considered.

The Culture and Management of Scylla Species (CAMS) project was a collaboration among four institutions worldwide – the University of Wales (Bangor) in the United Kingdom, Artemia Reference Center of the University of Ghent in Belgium, Can Tho University in Vietnam, and SEAFDEC/AQD in the Philippines. The CAMS project has reported on disease control and management projects in the Philippines and Vietnam. The objective: To improve the reliability and sustainability of crab hatchery systems through the use of probiotic bacteria as an alternative to microbials in disease control. The reports from the Philippines and from the Vietnamese research are available online. From the introduction:

For 2002 and 2003, monitoring activity of problems in large-scale hatchery rearing of crab larvae was done to identify windows of opportunity for probiotic application. These led to identification of various microbial fouling and disease-causing organisms in spawned eggs and hatchery-reared larvae.

Celia R. Lavilla-Pitogo and Leobert D. de la Pena, from the Aquaculture Department, Southeast Asian Fisheries Development Center Tigbauan, Iloilo, Philippines; published a report (December 2004) entitled Diseases in Farmed Mud Crabs Scylla spp.: Diagnosis, Prevention, and Control. From the forward:

Aquaculture production has suffered many set-backs due to the occurrence of diseases. Many of the diseases are caused by infectious organisms that are difficult to detect and need sophisticated instruments for diagnosis, but most disease occurrence and mortality in farmed aquatic animals are related to poor rearing water quality. It is, therefore, important for technicians and farmers to recognize the relationship between the animals they culture and the aquatic environment. The Government of Japan, through the Regional Fish Disease Project, funded research on diseases affecting mud crabs in order to come up with sound prevention and control methods.

This book is a collection of observations gathered from various research and commercial culture activities, and gives emphasis on disease recognition using simple techniques and gross observations of affected crabs. However, since many of the diseases are caused by microorganisms, microscopy is an important technique for their diagnosis. The authors of the book encourage active cooperation between farmers and diagnostic laboratories for disease identification, prevention, and control in order to build up more information to increase production. The Regional Fish Disease Project supports sustainable mud crab production and hopes that farmers and other users of this book will attain their production goals.

The report is located within a framed web site. Chapter 1 includes information about diseases in eggs and larvae. Chapter 2 includes information about diseases in juveniles and adults. The appendix includes documentation of various microscopy techniques. There is also a glossary.

A great deal of research into mud crab husbandry at academic levels and at more grassroot levels has been undertake in the Philippines. Esperanza A. Santos and Leah Charito T. Tambolero have written about a Bureau of Fisheries and Aquatic Resources – Fisheries Resource Management Project entitled Reviving a Coop: Rising Above Waters Through Mangrove Crab Culture. The coop also raised tilapia and prawns as secondary stocks. The authors report report: ‘After a full year implementation, the project provided substantial earnings for all the members of the coop. They hope that their learnings will be valuable lessons as well for those areas, families and people’s organizations interested to venture into mangrove crab culture.’

The Science and Development Network sumarises, and the New Agriculturalist reports on research to more closely integrate crab culture with sustainable mangrove management. From the introduction:

The rapid spread of aquaculture in recent decades has brought riches to some, ruin to many, exclusion to the poorest coastal dwellers, and environmental degradation. Scientists in the Philippines are adapting aquaculture to make it sustainable over the long term and suitable for small-scale, family-level operators. An innovative system of captive crab culture in live mangrove is being developed in the central Philippines and is now being verified and demonstrated on the southern island of Mindanao.

The Culture and Management of Scylla Species (CAMS) project was a collaboration among four institutions worldwide – the University of Wales (Bangor) in the United Kingdom, Artemia Reference Center of the University of Ghent in Belgium, Can Tho University in Vietnam, and SEAFDEC/AQD in the Philippines. The CAMS project has reported on aquasilviculture projects in the Philippines and Vietnam. The objective: To refine systems for integrated aquasilviculture of mud crabs within mangroves, specifically by reducing fish biomass requirement through low cost incomplete feeds and utilization of natural productivity. The aquasilviculture reports are available online.

Mud crabs, Scylla spp., also known as mangrove crabs, occur naturally in association with mangrove swamps and nearby intertidal and subtidal muddy habitats. Mud crabs can exceed 3kg in body weight, yielding high volumes of delicate flavoured meat and are accordingly sought after as a quality food item. Easily caught with simple traps or nets, they remain alive for considerable periods after capture and they are highly valued as an important income source for small-scale fishers throughout the Asia-Pacific region.

Scylla spp. seem to adapt to an aquaculture regime reasonably well, and they have been cultured in China for at least 100 years, and throughout the rest of the region for decades. In Japan, sea-ranching of hatchery reared mud crab seed has been employed but seed production has not proved reliable. Almost all crab aquaculture production relies on wild-caught stock, as larval rearing has not yet reached a commercially viable level for stocking into aquaculture farms. Megumi Minagawa, Takeshi Hayashibara, Motohiko Sano, Motoya Tamaki, Kouki Fukuoka, and Katsuyuki Hamasaki, from the Seikai National Fisheries Research Institute, have published a brief report (in English) entitled Habitat characters of juvenile mud crab, Scylla serrata.

In Australia, Clive P. Keenan, from the Bribie Island Aquaculture Research Center, has published a report entitled Aquaculture of the Mud Crab, Genus Scylla – Past, Present and Future. From the abstract:

Crabs of the genus Scylla are strongly associated with mangrove areas throughout the Pacific and Indian oceans and form the basis of substantial fishery and aquaculture operations. Aquaculture production currently relies on wild-caught seed for stocking ponds, as larval rearing at a commercial scale is still difficult. One of the major problems for effective mud crab management and aquaculture is the likelihood that there are a number of genetically distinct species. Research has demonstrated the presence of at least four distinct species. Laboratory experiments of the larval stages of each species should provide valuable information on each species’ biological and ecological requirements. There are two basic forms of land-based mud crab aquaculture: fattening of crabs with a low flesh content, and grow-out of juveniles to market size. Fattening is a very profitable activity, employing high densities of crabs and low costs. However, total production is low because of mortalities due to cannibalism. Grow-out systems for mud crabs show much more variety and production can be very high. Grow-out systems are usually pond-based, with or without mangroves, although intertidal pens can also be used. Without mangroves, lower stocking rates provide the best return. In shallow mangrove ponds, there are two distinct forms of aquaculture: (i) intensive, with higher stocking rates and supplemental feeding; and (ii) extensive, in large mangrove silviculture ponds where the stocking rate is very low, and no supplemental feeding is involved. Growth rates under all systems are comparable, with production of commercial-sized crabs three to four months after stocking with seed crabs. Further research is required into the habitat preferences of each species so that production techniques can be modified to suit their respective requirements. With advances in the hatchery production of mud crab juveniles for stocking into ponds and enclosures, the future of mud crab aquaculture looks promising.