312
Classical example of traditional brackishwater aquaculture is in practice in West
Bengal in the vicinity of Indian Sundarbans for centuries and these fisheries are
locally called as ‘Bhery’. In this method, low lying areas near the banks of saline
water rivers and creeks are encircled by peripheral dyke and tidal water is allowed
to enter in the impoundment along with natural seeds of various species of shrimps,
crabs and fishes. Water is retained with periodical exchanges during lunar cycles
and the animals are allowed to grow. After 3–4 months, harvesting is done partially
during lunar cycles. Productivity in this system ranged between 500–900 kg ha
−1
of
which about 30 percent is constituted by prawns/ shrimps and 70 percent by mullets
(Saha et al. 2001).
The age old traditional farming methods of fin fish and shrimp with some modification still exist because of their simplicity and cheapness. These are being gradually replaced by modern improved farming practices. Commercial shrimp farming
started gaining roots only during the mid-eighties. The boom period of commercialscale shrimp farming in West Bengal started in 1990 and the bust came in 1995–96,
with the outbreak of viral disease (Mehta 2009). Later with the advent of bio-secured
closed culture technology using better management practices, semi-intensive and
intensive shrimp farming started to regain its lost glory during early years of this
century. Following this method, farmers are getting production at the range of 4–6
tons ha
−1
(Sahu et al. 2012) with intermittent disease occurrences resulting crop
losses. In early nineties, shrimp farming was low risk and high profit venture; however the present form of shrimp farming has become low profit and high risk venture. The reasons behind decreasing profitability are abnormal hike in the input cost
and decreasing trend in the sale price of the product in recent years. Moreover, the
intensification of aquaculture, particularly shrimp farming has raised a range of
environmental concerns such as effluent discharge, excessive use of resources and
dependence on commercial feed (Granada et al. 2015). Viewing the risks associated
with shrimp farming and decreasing profitability, farmers have felt the need of
diversification to secure income and sustainability in very recent years.
Polyculture is potentially more sustainable than monoculture, due to the reutilization of waste products of one species by another (Petrell et al. 1993; Chopin
et al. 1999). Shrimp polyculture represents an important alternative to solving and/
or minimizing some of the problems (environmental pollution, diseases and decreasing prices) that shrimp aquaculture has faced in the past two decades. Several species from diverse trophic levels have the potential to be co-cultured with shrimps. A
good knowledge of the species that are candidates for polyculture and an adequately
designed culture system are the most important points to consider when co- culturing
shrimp with other species (Martínez-Porchas et al. 2010). Modification of age old
traditional brackishwater polyculture is a logical choice towards sustainable
intensification.
Selection of compatible species for better production and profitability is the first
step. Improved polyculture of shrimp with non-carnivorous fishes is a viable alternative to shrimp monoculture as a low cost low risk and high profit venture.
Improved farming practices like pond preparation, selective stocking, rational use
of formulated feed and proper pond management are the steps involved in improve9 Mangroves: A Source of Existing and Alternative Livelihood
Classical example of traditional brackishwater aquaculture is in practice in West
Bengal in the vicinity of Indian Sundarbans for centuries and these fisheries are
locally called as ‘Bhery’. In this method, low lying areas near the banks of saline
water rivers and creeks are encircled by peripheral dyke and tidal water is allowed
to enter in the impoundment along with natural seeds of various species of shrimps,
crabs and fishes. Water is retained with periodical exchanges during lunar cycles
and the animals are allowed to grow. After 3–4 months, harvesting is done partially
during lunar cycles. Productivity in this system ranged between 500–900 kg ha
−1
of
which about 30 percent is constituted by prawns/ shrimps and 70 percent by mullets
(Saha et al. 2001).
The age old traditional farming methods of fin fish and shrimp with some modification still exist because of their simplicity and cheapness. These are being gradually replaced by modern improved farming practices. Commercial shrimp farming
started gaining roots only during the mid-eighties. The boom period of commercialscale shrimp farming in West Bengal started in 1990 and the bust came in 1995–96,
with the outbreak of viral disease (Mehta 2009). Later with the advent of bio-secured
closed culture technology using better management practices, semi-intensive and
intensive shrimp farming started to regain its lost glory during early years of this
century. Following this method, farmers are getting production at the range of 4–6
tons ha
−1
(Sahu et al. 2012) with intermittent disease occurrences resulting crop
losses. In early nineties, shrimp farming was low risk and high profit venture; however the present form of shrimp farming has become low profit and high risk venture. The reasons behind decreasing profitability are abnormal hike in the input cost
and decreasing trend in the sale price of the product in recent years. Moreover, the
intensification of aquaculture, particularly shrimp farming has raised a range of
environmental concerns such as effluent discharge, excessive use of resources and
dependence on commercial feed (Granada et al. 2015). Viewing the risks associated
with shrimp farming and decreasing profitability, farmers have felt the need of
diversification to secure income and sustainability in very recent years.
Polyculture is potentially more sustainable than monoculture, due to the reutilization of waste products of one species by another (Petrell et al. 1993; Chopin
et al. 1999). Shrimp polyculture represents an important alternative to solving and/
or minimizing some of the problems (environmental pollution, diseases and decreasing prices) that shrimp aquaculture has faced in the past two decades. Several species from diverse trophic levels have the potential to be co-cultured with shrimps. A
good knowledge of the species that are candidates for polyculture and an adequately
designed culture system are the most important points to consider when co- culturing
shrimp with other species (Martínez-Porchas et al. 2010). Modification of age old
traditional brackishwater polyculture is a logical choice towards sustainable
intensification.
Selection of compatible species for better production and profitability is the first
step. Improved polyculture of shrimp with non-carnivorous fishes is a viable alternative to shrimp monoculture as a low cost low risk and high profit venture.
Improved farming practices like pond preparation, selective stocking, rational use
of formulated feed and proper pond management are the steps involved in improve9 Mangroves: A Source of Existing and Alternative Livelihood