Tech Forum Alert
Cage culture: cage construction, placement and aeration
Cages for fish culture have been constructed from a variety of materials and in practically every shape and size imaginable. Basic cage construction requires that cage materials be strong, durable and non-toxic. The cage must retain the fish, yet allow maximum circulation of water through the cage.
Adequate water circulation is critical to fish health in bringing oxygen into the cage, and removing wastes from the cage. Cage location in the pond is critical to proper circulation through the cage. Mechanical circulation and aeration through the cage may be necessary if stocking densities are high, cages are large, or water quality deteriorates during production.
Cage components consist of a frame, mesh or netting, feeding ring, lid and flotation, while cage shape may be round, square or rectangular. Shape does not appear to affect production with most freshwater species.
Cage size depends on pond size, availability of aeration, and the method of harvest. Most fish farming supply companies sell manufactured cages, cage kits or materials for constructing cages.
The simplest cage design to construct is a 4x4 feet cylindrical cage fashioned from 1/2-inch plastic mesh. The mesh comes in a roll four feet wide, and a total of 21 feet of plastic mesh is used for each cage. 13 feet of mesh is used for the cylinder with two four-foot panels for the bottom and lid.
Location of the cage in the pond can be critical to its success. Two factors to consider in cage placement are access to the cage and maintenance of water quality. Daily feeding and management of the cage necessitate easy access under almost any weather condition. Access may be by pier or by boat. Probably more critical to the success of the cage will be a location in the pond that allows for good water circulation.
Critical factors for locating a cage to maximise water quality are:
- Winds. It is important to locate the cage where it will receive maximum natural circulation of water through the cage. Usually, this is in an area that is swept by prevailing winds.
- At least six feet (about 1.83 metres) of water depth. A minimum of 2 feet of water is needed under the cage to keep cage wastes away from the fish.
- Away from coves and weed beds. Coves, weed beds and overhanging trees can reduce wind circulation and potentially cause problems.
- Away from frequent disturbances by people and/or other animals. Such disturbances will excite the fish and can cause stress, injury, reduced feeding and secondary disease. Fish are shy creatures and should never be disturbed needlessly.
- At least 10 feet between cages (unless aeration is available). Cages should not be too close together, or it may increase the likelihood of low dissolved oxygen and spread of diseases between cages.
Aeration can enhance water quality, reduce stress, improve feed conversion efficiency, and increase growth and production rates. Research has shown that aeration can improve cage production by 20 percent or more.
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Article made possible through the contribution of Oklahoma State University.
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