A fter a decade of experiments,cage farming of pearl spot fish or karimeen has been commercially launched in the Kerala backwaters in what is set to be a major boost to aquaculture.
The pearl spot fish declared the state fish last year is on the verge of extinction because of its unbridled exploitation due to its demand riding high on backwater tourism. Few tourists leave the state without relishing karimeen delicacies.
Now,Kumarakam (Kottayam) Research Centre of Kerala Agricultural University (KAU) has over a period of 10 years developed a technology called cage culture to spawn this expensive table fish in large numbers.
Inland fishermen,especially those in the backwaters of Kuttanad in Alappuzha,have been introduced to the new technology.
The Kerala fisheries department has issued 1,000 cages among 10 inland fishermen societies in Alappuzha and Kottayam. Harvesting of the first batch took place earlier this month.
According to Dr K G Padmakumar,associate professor (aquaculture),KAU,it is for the first time in India that open cage farming of pearl spot fish has been launched.
The cage farming of pearl spot can be done in both fresh and brackish waters,provided the flow is moderate. Cage culture has immense scope to arrest the dwindling fish wealth.
Under this practice,cages of a square meter size each and made of soft polythene are submerged in a water body,500 meters away from the shore. The cages have wooden pillars for support and their floors are covered with fine meshes so as to prevent loss of feed. The cages are moored to the lake bottom using concrete anchors.
Around 200 fingerlings or small fish,bred by a special stock and later reared in a hatchery,are placed in each cage.
The mortality rate of the fingerlings is nearly 10 per cent. Since fingerlings are vulnerable only in the first month of the six-month farming period,we can easily replenish the cage with new fingerlings if we lose them, said Padmakumar.
He said the high density of the fish in a cage ensures that the fish grow faster here than in a normal water body situation.
Also,fish reared through cage culture gains more weight,as they do not burn of energy owing to movement in a bigger water body.
While a pearl spot fish usually grows only up to 120-130 grams in six months,under cage culture its weight goes up to 250 grams in the same time period.
A major challenge that the practice faces as of now is the availability of special feed. In the initially days of the experiment,the research centre,which now maintains 240 cages,fed commercial prawn feed to the fingerlings. Later,the centre developed a special feed using desiccated coconut,rice bran and tapioca.
A natural advantage is that the pearl spot fish feeds on algae,which gets clogged in the cage net. But for the fish feeding on the algal growth,the cages need not to be cleared periodically to ensure that natural water flow is not blocked.
Also,as one batch of fish is harvested in six months,a cage can be used twice in a year.
According to Santhosh Kumar,secretary of a self-help group,which has 100 cages in the backwaters,polluted water disgorged from the paddy fields of Kuttanad,too,pose a threat to cage farming.
Kumar said all the fingerlings in a cage do not grow in the same pattern. After one or two months,therefore,the bigger ones need to be shifted to another cage. Harvesting has been staggered to prevent a glut the market,he added.
Assistant manager,Fisheries Department C Maniyappan said at present the cages have been distributed among those who used to make a living out of fishing in the backwater. However,the landless fishermen,too,can go for cage culture.
The state government has supplied fingerlings and the cage free of cost to the farmers. One kg of pearl spot fish fetches Rs 250-Rs 300 in the domestic market.