Scope and opportunities of cage and pen culture in open water systems
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Pampa Bhattacharjee
These are the aquatic resources where future enhancement techniques like pen and cage culture are to be adopted. Thus it is relevant to understand the present environmental status of these ecosystems.
What is Pen and Cage ?
Pen and cage are enclosures of any size shape and design and can be made of any suitable material. Pen and cage culture involve holding organisms captive within an enclosed space for short or long duration. There is confusion concerning the terms ‘cage culture’ and ‘pen culture’. Both terms are often used interchangeably, particularly in North America, where ‘pens’ and ‘cages’ describe the same method of culture. Hence a general term ‘enclosure culture’ is used to describe what more precisely could be defined as cage or pen culture. However still they are two different systems in many ways. A cage is totally enclosed on all or all but the top sides by mesh or netting, while in pen the bottom of the enclosure is formed by the lake or sea bottom (FAO). Pen has fixed enclosure walls cannot be moved about as in the case of cage. Fish grown in pens have access to benthic organisms, and there is some evidence that certain species grow better in pens than in cages.
Types of cage : Four types of cage are being used for cage aquaculture – fixed, floating, submersible and submerged:
Fixed cage, through very primitive in origin still in vogue, is used in shallow water with water depth 1 to 3 m in those reservoirs where water depth does not fluctuate too much and consisting of net bag fitted in posts and should not touch the basin. Fixed cages are comparatively inexpensive, simpler, and smaller in size & shape and their use is also restricted.
Floating cage, on the other hand, is basically supported by a floating frame, where from net bags are kept hanging in water without touching the basin. It is generally practiced in water bodies with depth of water more than 5 m. Enormous diversity of types- size, shape and design of this cage has been developed to suit the wide purpose of the fish growers in open waters.
The net bags of submersible cages are suspended from surface and with adjustable buoyancy – may be rigid or flexible.
The submerged net bags are fitted in a solid and rugged frame and submerged under water – use is very limited in reservoirs.
Shape of cage : Cage of different shapes is being used depending on the objective of cage culture, Normally, in reservoir, if the objective of cage culture is to rearfry to fingerlings, the shape would be square, rectangular or in some occasion circular type. The circular type cages are normally used in big reservoir with huge structure G.I./HDPE pipe frame.
It is stated that the circular type cages are best suited to the reared seeds so as to have more surface area; the only problem is that the shapes are to be maintained with proper mooring by fixed frame and not with sinkers. The cost effectiveness is to be viewed with priority while designing cages to be placed in open water like reservoirs.
Cage Culture Practices
Site Selection :The selection of site for cage culture is very important and success is in many occasions dependent on selection of proper site.
(To be contd)
These are the aquatic resources where future enhancement techniques like pen and cage culture are to be adopted. Thus it is relevant to understand the present environmental status of these ecosystems.
What is Pen and Cage ?
Pen and cage are enclosures of any size shape and design and can be made of any suitable material. Pen and cage culture involve holding organisms captive within an enclosed space for short or long duration. There is confusion concerning the terms ‘cage culture’ and ‘pen culture’. Both terms are often used interchangeably, particularly in North America, where ‘pens’ and ‘cages’ describe the same method of culture. Hence a general term ‘enclosure culture’ is used to describe what more precisely could be defined as cage or pen culture. However still they are two different systems in many ways. A cage is totally enclosed on all or all but the top sides by mesh or netting, while in pen the bottom of the enclosure is formed by the lake or sea bottom (FAO). Pen has fixed enclosure walls cannot be moved about as in the case of cage. Fish grown in pens have access to benthic organisms, and there is some evidence that certain species grow better in pens than in cages.
Types of cage : Four types of cage are being used for cage aquaculture – fixed, floating, submersible and submerged:
Fixed cage, through very primitive in origin still in vogue, is used in shallow water with water depth 1 to 3 m in those reservoirs where water depth does not fluctuate too much and consisting of net bag fitted in posts and should not touch the basin. Fixed cages are comparatively inexpensive, simpler, and smaller in size & shape and their use is also restricted.
Floating cage, on the other hand, is basically supported by a floating frame, where from net bags are kept hanging in water without touching the basin. It is generally practiced in water bodies with depth of water more than 5 m. Enormous diversity of types- size, shape and design of this cage has been developed to suit the wide purpose of the fish growers in open waters.
The net bags of submersible cages are suspended from surface and with adjustable buoyancy – may be rigid or flexible.
The submerged net bags are fitted in a solid and rugged frame and submerged under water – use is very limited in reservoirs.
Shape of cage : Cage of different shapes is being used depending on the objective of cage culture, Normally, in reservoir, if the objective of cage culture is to rearfry to fingerlings, the shape would be square, rectangular or in some occasion circular type. The circular type cages are normally used in big reservoir with huge structure G.I./HDPE pipe frame.
It is stated that the circular type cages are best suited to the reared seeds so as to have more surface area; the only problem is that the shapes are to be maintained with proper mooring by fixed frame and not with sinkers. The cost effectiveness is to be viewed with priority while designing cages to be placed in open water like reservoirs.
Cage Culture Practices
Site Selection :The selection of site for cage culture is very important and success is in many occasions dependent on selection of proper site.
(To be contd)