The Central Marine Fisheries Research Institute (CMFRI) has come out with a report pointing out that the increasing number of puffer fish on our seas is owing to the decline in the number of large predatory fish.
The dramatic increase in the number of the puffer fish is a major concern for the fishing communities in Kerala, Karnataka and Tamil Nadu. The fish which bites at the nets and the catch were found to be causing damages worth crores of rupees in the sector. Based on the figures on the availability of various fish, Express had earlier reported that the increasing number of these fish could be due to the decline in the number of predatory fishes.
The CMFRI has now concluded that there are signs of a phenomenon called tropic cascade in the Arabian Sea. It refers to dramatic changes in the structure of the ecosystem owing to the addition or removal of top predators. The changes in the predator population has a reciprocal impact on the relative populations of the prey through the food chain. The study, which will be published in the February edition of Current Science, pointed out that the puffer fish had been meagre in Kerala from 70s to the 90s. But by 2006, there has been a steep increase in the catches, and in 2011, within five years, it was close to 2,000 tonnes.
Meanwhile, its predators, including the Kingfish, catfish and sharks, were showing an opposite trend. The catfish had shown a drastic decline in its catches, and from 1985, it has the status of a collapsed stock. Meanwhile, the catch of kingfish has come under severe fishing pressure lately and have declined by 44 per cent from 2007. Sharks have declined by over 70 per cent, and they have been classified as close to depletion. The start of the decline in the Cobia catch in 2007 and the start of the increase in puffer catch the same year are strongly coincidental, the report notes.
The report recommends a close watch and the monitoring of the population biomass changes and abiotic factors to understand such phenomena.