Cage Fish farming in Kerala | Cage Culture
Cage culture is one the best method to cultivate fish in a natural habitat like pond, river, lake and sea. Cage culture, unlike the recirculating aquaculture system, is netted colonies where we cultivate fish in its natural habitat.
In Cage culture system of fish farming, we utilize existing water resources, but the fish are cultivated in cages and basket which allows the water to pass freely between the fish and thereby facilitating water exchange and waste removal into the surrounding water.
The first cages appeared in Southeast Asia around the end of the 19th century, then Wood or bamboos were used to construct cages and In 1950s modern cage culture began with the invention of synthetic materials for cage construction.
Following is a small model of cage frames and nylon net placement in cage culture.
In Kerala first of all, we have to procure the appropriate permission from the Central Maine fisheries research institute C.M.F.R.I. And Get the N.O.C certificate from your local panchayath/municipality before starting up any such activities in ponds, rivers, lake and sea.
Following are some major points to observe before doing cage farming or net farming.
Cage frames and net
Feeds and feed management
1) Site selection:
Since we are blessed with 3 types of water source in Kerala the choice can be made easily. The three types of water sources are seawater, brackish water and fresh water.
Therefore finding a good location for farming is very important. The location should be easily accessible, where you can have a small storeroom and facility to keep staff for caretaking and safety.
(These cages are floated with help of HDPE barrel 200 litre. These are made with a square tube - Location - Periyar lake)
The chemical parameters of the water source should be studied in detailed. The parameters like oxygen concentration, temperature, salinity, tides/water exchange, algal blooming, pollution, wave action, etc are to be monitored and recorded before starting up any kind of activity.
The clear depth of the water body should be measured and recorded for a suitable period of time so that this information comes in handy while planning the size and location to dock the cage.
2) Cage Size:
The fish cage design is done only after a detailed study about the site is conducted, wrong selection of materials, design and construction can lead to fatalities.
The cage size is decided as per the data collected and recorded in relation to the location of the proposed cage or net farm. For seed rearing C. M. F. R. I have developed a method of 6 m Dia and 15 m Dia and 2 m Dia HDPE cages.
The the best size for a cage to stock fish is 6 Mtr x 4 Mtr x 2 Mtr. This unit can be incorporated with a custom size happa net for seed rearing.
3) Cage Frames and Net:
The cage can be made in different size and shapes according to customers requirements and site conditions.
The main structure of the cage can be constructed using any materials which will not rust easily and will have the necessary strength to hold the weight of the Net and fishes.
Many materials of choices are available to use like GI pipe, PVC, bamboo, square tube etc for making a cage.
There are different material options available in the market which are suitable for constructing the cage frames. For example H.D.P.E, P.V.C frames are expensive but they last for many farming seasons.
G.I have less life span compared to H.D.P.E and P.V.C. G.I have less life span in Seawater and brackish water but in freshwater lakes like Periyar, it will last many many years.
There are different dimension and materials examined for cage culture in India one should select the best suitable material by analyzing the data collected regarding the proposed farm location.
Commonly Nylon twisted nets are widely used for cage farming, which is also economically viable. These nylon nets are very durable and if properly cared and maintained can withstand many years of use.
Nylon nets are very light in weight so in order to keep the nets straight in the water lead weights are added. There are two types of net one for the inner unit and another net for outer, there is a gap of 35 cm between two nets which run along both side and bottom.
The stocking density will vary from the variety of fish seed but the good management of cage farming and ideal location can have the yield up to 20 to 40 kg/m3.
Quality of fish feed and seeds can make a big difference in the growth and mortality rates.
5) Feeds and Feed Management:
The type of feed purely depends on the breed of fish cultivated. Types of fish feed include fresh or frozen fish, green leaves, floating dry pellets all these are commonly used to grow fish.
Feeding can be done either with feeding trays but it's not easy to feed on flowing water body for that we have to cover garden net by the side from 8 inches from top to the water level. To avoid the feed to flow through the net.
Automated fish feeders with adjustable discharge Quantity of feed can be used to deliver the correct quantity of feed to the fish each and every time. Wastage of food can be avoided by using such an automated system.
Feeding the fish on time and according to the demand will help in their rapid growth.
6) Cage management:
Cage management is one of the very important steps in the cage farming method, proper cleaning of the net very vital for the healthy growth of the fish seeds.
Cleaning of the nets should be done once in a week to avoid algae growth on the net. Clean nets will provide better circulation for water and thereby supplying the essential nutrients to the fishes.
It is advised to cover the cage unit with birds net to avoid birds attack. Look out for turtles in the vicinity of the farm as turtles can cut and damage the net.
For more advice on fabrication and setting up of cage farms, or Aquaculture facilities with filters and other necessary accessories kindly contact us.