Cage Culture of Freshwater Fish

What is Cage Culture

Cage culture is an aquaculture production system where fish are held in floating net pen. Cage culture pf 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 matine waters. Cages in freshwaters are used for food fish culture and for fry to fingerling rearing.

The origins of cage culture are a little vague. It can be assumed that at the beginning fishermen may have used the cages as holding structures to store the captured fish until they are sent to the market. The first cages which were used for producing fish were developed in Southeast Asia around the end of the 19th century. Wood or bamboos were used to construct these ancient cages and the fish were fed by trash fish and food scraps. In 1950s modern cage culture began with the initiation of production of synthetic materials for cage construction. Fish production in cages became hightly popular among the small or limited resource farmers who are looking for alternatives to traditional agricultural crops.

Cage Culture - Definitions

Cage is an enclosed space to rear organisms in water that maintains free exchange of water with the surrounding water body. 'Pens' are essentially portions of a water body cordoned off by erecting a fencing like structure. Usually pens are enclosed portions of the lake margin, with fencing on three sides; the free fourth side being contiguous with the land. But, pen can also be away from the shore with fencing on all the four sides. The main difference between a pen and a cage is: pen bottom is never covered so that the soil water interface of the water body is not compromised. Enclosure aquaculture in the context of inland fisheries in India refers to both 'cage culture' and 'pen culture'. The document deals exclusively with cage culture.

Site Selection

Criteria for site selection are based on safety of the location and smooth culture operations avoiding or minimising user conflicts. Thus, the sites to be avoided are: (1) places with turbulence and excessive wave/wind action, (2) bad water quality, (3) water bodies with obstructions and heavy weed infestation, (4) low depth, (5) difficult to access the site and logistic considerations and (6) nearness to dense human habitation, dams, tourist spots, industries and polluting industries. Area of fish nursery and breeding grounds, sensitive areas like pilgrimage centers, water bodies for public use like drinking water, cleaning, navigation, etc. and protected aquatic reserves, sanctuaries, etc. ate also to be avoided. The ideal locations for siting cages in large and medium reservoirs are the protected bays/coves to avoid damage due to strong wind action. However, some mild turbulence always helps exchange of metabolites and nutrients between the cage and outside environment. By using these basic criteria, water bodies or specific locations within a water body can be chosen for cage culture. This information can be included in a map to be prepared at district and State level. The State Department of Fisheries should take initiatives of their own to select the suitable reservoirs and the sites therein for cage fish farming and draw-up maps in GIS plateform to facilitate easy planning. However, if neccessary they can take the advice of experts from the concerned ICAR and Central Institutes.

Advantages and Disadvantages

As with any production system, fish culture in cages has advantages and disadvantages that should be considered carefully before choosing it as the production model.

Advantages

Following ate the advantages of cage culture when compared to the other fish farming

systems:

  • its installation is easy.
  • flexibility of management.
  • effective use of fish feeds.
  • less manpower requirement.
  • better control of fish population.
  • in emergencies it can be removed from one place to another.
  • treatment of disease is much simple than that of pond culture.
  • It requires less investment, because it use existing water bodies, and simple technology and swift return of investment
  • controlling the unwanted reproduction of tilapia, therefore mixedsex populations can be rered in cages.
  • close observation and sampling of fish is simple and therefore only minimum supervision is needed
  • many types of water resources can be used, including lakes, reservoirs, ponds and rivers.
  • fish handling and harvesting are very simple and helps to maintainm the non-seasonal supply of the fish.
  • Since the cage is meshed, fish inside have less changes of being attacked by predators.
  • They can be used to clean up eutrophicated waters through culture of caged planktivorous species such as silver carp.

Please feel free to ask any question.