Shrimp aquaculture in the Ganges-Brahmaputra-Meghna delta

Shrimp aquaculture started in GBM delta during 1980s and mainly within coastal polders. It expanded rapidly where salinity was suitable. However, there was much concern on environmental and social grounds due to mal-practice of shrimp culture and diseases. In course of time, shrimp culture practice and areas of shrimp culture changed and mix culture took hold at many places. Integrated or mix farming with less environmental and social conflicts appears to have great potential as an adaption option to climate change in the coastal zone. Recently, a field survey has been conducted to learn more about this adaption option and appears to hold great promises.

It has been found that integrated farming is propagating in areas with salinity lower than 15 ppt. Various forms of integrated and mix farms can be seen. Such farms adopts a combination of crops such as brackish water shrimp (bagda), freshwater shrimp (golda), tilapia, other fin fish, crab, horticulture/agriculture (dry season vegetables and paddy) and Geese/duck. Usual cropping pattern would be Bagda-Paddy, Golda-Paddy, Golda-Bagda-Agriculture. These integrated farming systems are developed by farmers through trial and error with little extension support from line agencies. However, such integrated approaches usually are difficult to be supported by single line agency. Extension support for such integrated farming will require a completely different extension model. These integrated approaches would be more resilient, cost effective, rational use of resources to climate change condition.

It is apprehended that in climate change condition new areas of GBM Delta will be inundated and salinity will intrude farther. Many areas may not remain suitable for paddy farming and may be considered for shrimp aquaculture. In such situation only good practices with integrated form may be one of the adaptive solutions. Based on investigation made during 2015-16 by IWFM, BUET under DECCMA study, several integrated and sustainable shrimp farming practices in Chitalmari and Fakirhat of Bagerhat District has been found where horizontal and vertical expansion of this aquaculture pattern absorbed seasonal and local unemployed youth including women. It is observed that in these areas farmer opted brackish water shrimp in one season and freshwater shrimp in another season. In between, farmers considered Tilapia and other fin fishes and also horticulture/agriculture. The yield and income has been profitable and sustainable. There are indications that such integrated/mix farms reduces migration too.

So far, integrated farming is mostly seen in the Khulna region. It is not seen much in Barisal or Chittagong region. With climate changed condition it is estimated that more areas will become brackish especially in some areas in Pirojpur, Jhalokathi and Barisal. It is apprehended that people would prefer mix shrimp-fish culture (towards integration) as salinity level will not be high to choose for Bagda alone and not so less to continue with rice farming. So there will be scope for integrated fish-shrimp-horticulture. Thus, existing coverage of integrated farming though not very high but in future it will be considerable especially if there is adequate extension support. In future, integrated farming involving marine fish may also take hold where salinity would be little high. Again it will require new form of extension services.

Integrated shrimp aquaculture also observed other Deltas under DECCMA study. In Mahanadi Delta in India especially in the Chandipur area at the outfall of Subarnarekha River within permissible salinity range. In Volta Delta in Ghana Shrimp Farming not yet flourished. One farm established in 2013 (including a hatchery) in the Ada East District and created job opportunity for many people.