Description

Freshwater prawn (Macrobrachium rosenbergii) cultivating is presently one of the main areas of the public economy, and during the most recent twenty years its improvement has drawn in significant consideration in light of commodity potential. The freshwater prawn is an exceptionally esteemed item for worldwide business sectors; practically all prawns are subsequently traded, especially to the USA, Europe and Japan. In 2006, Bangladesh sent out 49,317 tons of prawn and shrimp esteemed at US$415 million, of which around 25% was contributed by prawn (DOF 2007).

The all out region under prawn development is assessed to be around 50,000 ha. Most prawn ranches (71%) are situated in southwest Bangladesh, basically Khulna, Bagerhat and Satkhira regions (Ahmed et al. 2008). Freshwater prawn cultivating is growing quickly at a normal of 10% per annum. Roughly 1.2 million individuals are engaged with prawn and shrimp creation, handling and promoting exercises, and a further 4.8 million family individuals are related with the area. What's more, the livelihoods of around 400,000 individuals, large numbers of them ladies and kids, are related with prawn and shrimp fry fishing in beach front Bangladesh (USAID 2006).

In southwest Bangladesh, the development of prawns is finished in altered rice fields, privately alluded to as gher. The Bengali expression 'gher' is a nook made for prawn development by changing rice fields through building higher dams around the field and exhuming a channel a few feet somewhere inside the fringe to hold water during the dry season (Kendrick 1994). Gher cultivating is a peaceful, native innovative unrest, reasonable for the development of prawn, fish, rice and dam crops. This development, joined with excessive costs for prawn in the worldwide market, has driven expanding quantities of ranchers to change over rice fields to prawn ranches. Prawn cultivating in rice fields can be considered as a technique for coordinated hydroponics horticulture (IAA). IAA is more fitting for asset unfortunate ranchers who incorporate joining with rice or different harvests. IAA cultivating frameworks are frequently safer on the grounds that, whenever oversaw effectively, they benefit from synergisms among undertakings. The reasons for IAA are expanded expansion, heightening, further developed normal asset proficiency, expanded efficiency and maintainability.

Harvesting of Prawns

The quick improvement of coordinated prawn cultivating in southwest Bangladesh has been compared to a 'blue revolution'1 (Ito 2004; Islam 2007). The term 'blue insurgency' alludes to the surprising development of hydroponics as a significant and exceptionally useful agrarian movement. The blue upheaval is the consequence of new procedures of fish cultivating that might add to human sustenance in manners practically identical to the 'green upset', yet may likewise make social and natural issues. Noticed that one method for making the blue unrest all the more ecologically adequate is to show new strategies to unfortunate ranchers. It is being stated similarly as the 'green unrest' changed world agribusiness during the 1960s.

There are two prawn cultivating frameworks in Bangladesh: lake and gher. Around 71% of ranchers are associated with gher frameworks and the rest of lake frameworks. Despite the fact that prawn cultivating practice is as yet customary and broad in nature, numerous ranchers (20%) practice further developed strategies where prawns are developed semi-seriously. Broad creation commonly utilize marginally changed variants of conventional techniques and are called low-thickness (10 000^18000 postlarvae ha 1 year 1) and low-input framework. The framework depends fundamentally on normal efficiency (e.g., phytoplankton, zooplankton and benthos) of the lake, however natural and inorganic manures are infrequently used to advance the development of regular food sources. Broad taking care of practices by and large utilize strengthening consumes less calories comprising of a combination of locally accessible feed fixings, for example, rice grain, wheat grain, oil cake and fish dinner. Semi-escalated tasks practice middle degrees of loading (18000^30 000 post hatchlings ha 1 year 1) and different sources of info. Ranches with semi-escalated taking care of practices rely upon economically produced pelleted.

Valuable feeds are involved by all ranchers in gher frameworks. Various feeds are utilized yet the favored feed is the freshwater snail, Pila globosa. The utilization of snail meat as prawn feed is far reaching in prawn cultivating regions and snail populaces are accounted for to have declined vigorously because of unreasonable reaping. A wide assortment of individuals including ladies and youngsters are engaged with snail collecting during June to October. Generally, the stock of snails has produced various work valuable open doors, in getting, handling, shipping and showcasing exercises.

Feeds and Feeding of Prawns

A typical 66.5 kg ha 1day 1 of snail meat is applied for taking care of prawns during June to October. By and large, hacked snail meat is allowed two times every day toward the beginning of the day and night. If over the top snail meat £oats up in the water, feed supply is decreased, and it is expanded on the off chance that it doesn't £oat in the water. The stockpile of snail is unpredictable and thusly ranchers additionally utilize natively constructed feed blending by cooked rice, rice wheat, oil cake and fish dinner, or now and again utilize economically fabricated pelleted feed. In the mid-1990s, most of pelleted feed was imported from Thailand and Taiwan, while most ranchers presently utilize privately made pelleted feed for prawn cultivating.

The typical yearly yield of head-on prawns in Bangladesh was accounted for to be 336 kg ha 1. The current creation levels recommend that the typical efficiency of prawn has expanded lately, most likely as ranchers have become more sure to increment loading densities and taking care of levels. In the mid-1990s, the typical yield of prawn was only168 kg ha-1, which was low because of the customary cultivating technique and the somewhat low degree of data sources. Nonetheless, in the last part of the 1990s, revealed yields had expanded, with a common yield of 200^250 kg ha-1 being gotten, while Hoq, Islam and Hossain (1996) detailed that prawn creation when raised along with fish, changed from 162 to 428 kg ha-1. By and by, the greater part of the prawns are developed involving broad techniques in Bangladesh and efficiency is low contrasted and different nations. Nations with a bigger product market than Bangladesh utilize more escalated strategies and have fundamentally better returns.