SOCIAL AND ECONOMIC IMPACTS OF THE FARMING

Social impacts
Description of the supply chain
Whilst there are variations from country to country, the supply chain from the collection of a juvenile crab may include one or more middlemen to a farmer, and then from a farm a further number of middlemen to an exporter, or if for local trade to a retailer (Cholik and Hanafi, 1992). In some countries the crabs marketed locally are often those that are not of sufficient quality to be exported (Khan and Alam, 1992).

The supply chain often has an additional link in it which includes mud crab fattening. Where fishermen or farmers harvest post-moult or “empty” crabs, these may be send to a farmer who specializes in fattening crabs (Rattanachote and Dangwatanakul, 1992).
How does aquaculture change supply chain arrangements
The major change in the supply chain occurs if hatchery operations are introduced into the industry. In time, growth of the hatchery sector for mud crabs may result in collectors of wild seed loosing a source of income if farmers favour hatchery stock over wild. There are a number of reasons why hatchery produced stock would in time be favoured by farmers. Stock would be of a more uniform size (minimizing cannibalism), of just the one species and also available in large numbers on a year-round basis.

However in the short- to medium-term, the demand for mud crab seed-stock in most countries would indicate that collection of wild stock will remain a viable fishery for some time, subject of course to sustainability issues.
How does aquaculture influence employment and skill development
In Bangladesh it was reported that most crab catchers are otherwise jobless and landless (Khan and Alam, 1992). As more hatchery operations for mud crab start up there will be an increased demand for skilled and semi-skilled technicians, and for training programmes to support such development. Viet Nam has developed a very successful train-the-trainer programme in mud crab aquaculture which has supported the rapid expansion of the mud crab hatchery sector in that country (Shelley, 2004b).
With hatchery production of crab seed-stock, the expansion of the industry will not be limited by the supply of wild seed-stock in the medium to long term. As a result the industry is expected to expand dramatically over the next few years. This will stimulate a demand for more workers to manage ponds, harvest and pack crabs and in support industries such as feed production, transportation and construction.
Economic issues
Winners and losers
In the Philippines, Aldon (1997) provided advice on how to establish and operate mud crab culture in mangrove areas. Information on the economics of such a venture indicated that a return on investment of 44 percent was possible, with a payback period on establishment costs of 2.27 years. This was based on a production yield of 600/kg/h-1 and survival rates of 65–70 percent. A similar model from the Philippines (Baliao, De los Santos and Franco, 1999a) had a payback period of 1.4 years.
Mud crab aquaculture is now commonly being undertaken in enclosures or pens in mangrove forests (Baliao, De los Santos and Franco 1999b; Chang Wei Say and Ikhwanuddin, 1999; Rodriguez, Trino and Minagawa, 2001; Trino and Rodriguez, 2002). This is putting a significant value on mangrove forests and encouraging their conservation and in some places re-planting. Whilst mangrove enclosures are productive systems for mud crab aquaculture, the mangroves themselves are also valuable and critical to sustain wild mud crab fisheries (Ronnback, 2001).