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Shanghai Crab Symposium

CHINA - The Shanghai Crab Symposium last year brought together scientists, farmers and fisheries officers from 18 countries with one thing in common crabs.

In the opening ceremony Professor Patrick Sorgeloos challenged participants to push past the current ‘magic’ of some established aquaculture technologies; answer the hard questions – why does it work (or not) – often through basic research; so that truly industrialised farming technologies, based on good science can support the blue revolution needed to meet the seafood demands of tomorrow.

The meeting presented perhaps the first major opportunity for Chinese scientists and farmers to share with the international community their knowledge, science and experience behind the amazing growth of crab aquaculture in China over the past two decades. In addition it provided a forum for strong and diverse contributions to crab biology needed to support the culture and fisheries management of a range of crab species.

Over the last 20 years, Chinese Mitten Crab farm production in China has grown from the first reported annual production of just over 3000 tonnes, to an estimated 500,000 tonnes per annum today. It is now grown in every Chinese province except Tibet. Mitten crab farming in China is mostly conducted at low stocking densities, often integrated with other land use, over very large areas of coastal and inland wetlands.

In addition China is now the largest producer of farmed mud crabs, Scylla spp., and the swimming crab, Portunus trituberculatus, at over 106,000 tonnes and 100,000 tonnes per annum respectively. The farmed production of the swimming crab is becoming increasingly important as the country’s fishery for this species (400,000 tonnes per annum) is considered overfished. Crab farming development in China has benefited from strong government funding, and collaboration of multiple research teams from various universities and research institutes.

Vietnam also reported impressive growth in mud crab aquaculture production in recent years from just 3000 tonnes in 1995, to 10,000 tonnes in 2004, and an estimated 30,000 tonnes this year. One third of the Vietnamese production is based on crablets produced in hatcheries. In the Philippines hatchery production of mud crabs is also increasing, with private hatcheries now using technology developed by the South East Asian Fisheries Development Centre, and the University of the Philippines in the Visayas.

In the case of mud crabs, their growth in production has largely been made using low-density farming systems, many of which practice polyculture, and have so far avoided the widespread disease problems typically associated with intensification. This makes farming crabs a highly attractive sustainable livelihood option, producing high value products with low environmental impacts. In many Asian countries, including the Philippines and Vietnam, mangrove friendly production of mud crabs is taking place in simple production pens, sometimes together with silviculture.

In addition to the rapid growth in production for the major farmed crab species, the symposium highlighted the increasing number of species of crab currently being cultured, which includes the European Shore Crab (UK), the spider crab (Spain), red crab (Alaska) and the blue crab in Chesapeake Bay (US).

Another exciting revelation from the meeting was that a number of successful stock enhancement trials of various crab species have now taken place around the world (USA and Japan), demonstrating the potential for hatchery produced crab stock to successfully support the recovery of wild stocks when fishery management fails.

The symposium had a significant high tech component, with DNA analysis, molecular markers, and functionality of genes and enzymes expanding the understanding of a range of crab species. The obvious challenge was to develop strategies to ensure that these results led to direct benefits to farmers, who are still using low-tech production systems.

The large number of quality student presentations at the symposium identified a new generation of professionals working on crab research to address the problems and opportunities for both large-scale culture, and management of crab fisheries.

Like all good symposiums, it concluded with a workshop that summarised the status of today’s knowledge and looked to the future. Sustainability, of both crab fisheries and farming systems; future hatchery technology; disease management; development of specialised crab feeds; domestication of stocks for farming; economic analysis to drive future research; and techniques to reduce cannibalism of crabs during grow-out were identified as important themes for further consideration and action.

The Shanghai Crab Symposium highlighted the importance of successful management of the world’s crab fisheries to regional economies, and the market driven growth of crab aquaculture, in particular in China and southeast Asia. It also identified a real need for concerted international collaboration in research, farming technology and fisheries management to optimise the benefits of the world’s crab resources within an ecologically sustainable development framework.

The symposium’s scientific committee urged that the sustainable expansion of crab culture should include responsible approaches to integrated management of coastal ecosystems to prevent the environmental problems that have developed with intensive and widespread culture of other species.

For further information, please contact: Dr Chaoshu Zeng, School of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia; Tel: +61 747816237; Fax: +61 74781 4585; Email: chaoshu.zeng@jcu.edu.au.

the Fish Site Editor

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