Cage Aquaculture System

Cage culture is an aquaculture production system where fish are held in floating net cages. Cage culture of fish utilizes existing water resources but encloses the fish in a cage or basket which allows water to pass freely between the fish and the pond permitting water exchange and waste removal into the surrounding water. Cages are used to culture several types of shell fish and finfish species in fresh, brackish and marine waters. Cages in freshwaters are used for food fish culture and for fry to fingerling rearing. Fish production in cages became highly popular among the small or limited resource farmers who are looking for alternatives to traditional aquaculture practices

. Today cage culture is receiving more attention by both researchers and commercial producers. Factors such as increasing consumption of fish, declining stocks of wild fishes and poor farm economy has increased interest in fish production in cages. Many small or limited resource farmers are looking for alternatives to traditional agricultural crops. Cage culture also offers the farmer a chance to utilize existing water resources in which most cases have only limited use for other purposes

Potential species and criteria for selection of species for cage culture:

The selection of species for cage culture should be based on a number of biological criteria such as omnivore or carnivore, hardiness, fast growing, efficient food conversion ability, availability of quality seeds, disease resistance and market demand. Potential high value fish species suitable for cage culture are- Channa striatus, Channa punctatus ompok spp chitala, Clarias magur, H. fossilis, Pangasius sutchi, GIFT tilapia and high yielding variety of carp such as Amur carp and Jayanti Rohu

Stocking:

Although stocking densities should be determined by species requirements and operational considerations, the influence of stocking densities on growth and production has been determined empirically. The stocking density depends also on the carrying capacity of the cages and the feeding habits of the cultured species. Optimal stocking density varies with species and size of fish. For grow-out, the stocking density is in the range of 60 to 100 nos./m3 of fingerlings (50-60 mm size). For seed raising, stocking density of 250 to 300 fry/m3 found to give good result in terms of growth and survival

Advantages

Cage culture has advantages which include:

• Many types of water resources can be used, including lakes, reservoirs, ponds, strip pits, streams, and rivers which could otherwise not be harvested.
• A relatively low initial investment is required in an existing body of water.
• Harvesting is simplified.
• Observation and sampling of fish are simplified.
• Allows the use of the pond for sport fishing or the culture of other species.
• Less manpower requirement.
• Generation of job opportunities for unemployed youth and women.
• Additional income to fishers during closed seasons.

Cage management:

Cage culture management must result in optimizing production at minimum cost. The management should be so efficient that the cultured fish should grow at the expected rate with respect to feeding rate and stocking density, minimize loss due to disease and predators, monitor environmental parameters and maintain efficiency of the technical facilities. Physical maintenance of cage structures is also of vital importance. The net-cages must be routinely inspected. Necessary repairs and adjustments to anchor ropes and net-cages should be carried out without any delay. Exchange of net should also be considered, as this ensures a good water exchange in the net, thereby washing away faeces, uneaten food and to a certain extent reduce the impact of fouling.

Disadvantages:

• Fishes cannot feed themselves- Inside cage culture, fishes cannot acquire their food naturally and must be fed regularly by the farmer. It is important that their feed has all of the necessary nutrients, vitamins, and minerals for their proper growth.
• Limited production- It has been noted that fewer pounds of fish per acre are produced in cages than in open pond cultures. Limited production is caused because of poor water quality, fish density, and increased incidence of disease.
• Poaching- Cage cultures are easy targets for poachers and vandals. Therefore, to reduce the risk of poaching and vandalism, the farmer must set up their cage in a place where access to the cage is limited.