Environmental damage threatens prawn farming in Bangladesh

South-west Bangladesh is densely populated and most families are poor. Freshwater prawn farming is an important source of income. In recent years, the high demand for prawns overseas has greatly increased local earnings. However, productivity is lower than in other exporting countries, such as Vietnam. Extensive prawn production is also creating environmental issues, such as overharvesting of species.

Research from Bangladesh Agricultural University and the University of Stirling, in the UK, investigates traditional prawn farming in south-west Bangladesh. Farmers use a ‘gher’ system, which is a modified rice field with a high, broad dike around it and a deep canal to hold water during the dry season. Most gher farmers integrate prawn farming with fish and rice production.

The research took place in Bagerhat district, a coastal area in the Bay of Bengal, during the peak prawn farming season between May and January. The researchers surveyed gher farmers, and also interviewed collectors of post-larvae (prawns just beyond the larval stage), traders in fry (newly hatched fish), snail harvesters, and prawn traders.

The research shows that 82 percent of farmers have improved their standard of living through using gher systems. Benefits include better housing and transport, and more purchasing power and choice. The most significant change is that they are able to eat more frequently and enjoy better quality food.

However, the remaining 18 percent of farmers have not specially benefited from prawn farming and some have become poorer. A third of these blame their failed harvests on the lack of technical knowledge.

Other important findings include:

• Forty three percent of the farmers surveyed identified the high costs of producing prawns as their single most important constraint.
• Particular problems included the shortage and high price of wild fry, increased wage costs and problems accessing credit.
• Other constraints included water pollution, natural disasters such as flooding and drought, and crimes including poaching and the deliberate poisoning of stocks.
• Wild prawn stocks decreased due to the uncontrolled harvesting of post-larvae.
• Farmers reported higher prawn yields and lower production costs when using snails as feed, compared with home-made or other types of feed.
• However, the snail population have also declined due to excessive harvesting, and snails were now harvested from neighbouring districts.

Most prawns in Bangladesh are cultivated using extensive methods, which reduce productivity. The researchers conclude that training and technical support for farmers, for example in management skills, as well as higher inputs and better technology, could reduce the risks of prawn farming and improve profits. They also note:

• Although using hatcheries to produce prawns is technically possible in Bangladesh, it has not yet been effectively established.
• More prawn hatcheries may reduce the pressure on wild post-larvae and increase wild populations, compensating for the possible shortage of prawn fry.
• Low-cost, locally produced feeds may increase farmers’ profits and reduce the negative environmental impacts of snail harvesting.
• The widespread construction of gher systems is likely to result in the loss of wetland biodiversity, which in turn reduces rice production and increases flood risks.

Source(s):
‘Freshwater Prawn Farming in Gher Systems in South-west Bangladesh’, Aquaculture Economics & Management, Volume 12, pages 207 to 223, by Nesar Ahmed, Janet H Brown and James F Muir, 2008 Full document.

Funded by: UK Department for International Development (DFID)

id21 Research Highlight: 1 March 2009

Further Information:
Nesar Ahmed
Department of Fisheries Management
Bangladesh Agricultural University
Mymensingh-2202
Bangladesh

Contact the contributor: nesar_2000@yahoo.com

Department of Fisheries Management, Bangladesh Agricultural University, Bangladesh

James F Muir
Institute of Aquaculture
University of Stirling
Stirlingshire FK9 4LA Scotland
UK

Contact the contributor: j.f.muir@stir.ac.uk

Institute of Aquaculture, University of Stirling, UK

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