Fish in troubled water

Thanks to climate change and global warming, the typical fish species of the Kerala coast, sardline (mathi) and mackerel (ayala) are expanding their habitat to the northern and eastern coasts of the country. The mackerel, also showed a shift in the depth of distribution. Until many years ago, the sea surface-temperature (SST) along the Gujarat and Maharashtra coasts were slightly lower than along the Kerala coast, this being the reason as to why the two fish species were confined to the southern regions of the western coast. They were not seen in the eastern coast at all. Now, with warming of the sea surface, especially along the northern regions of the west coast and the whole of east coast, these fish are able to fine the temperature to its liking and try out new waters. This was observed by the scientists of the Central Marine Fisheries Research Institute (CMFRI), Kochi, as part of their study on 'Impact, Adaptation and Vulnerability of Indian Marine Fisheries to Climate Change'."The problems for the fisheries sector, as a result of climate change is high. This is besides the issues such as depleting fish stocks and competition among stakeholders," said Principal Scientist E Vivekanandan, who is heading the project.A rise in temperature as small as one degree Celsius (1 C) can have rapid and important effects on the mortality of some organisms. The oil sardine, Sardinella Longiceps, and the Indian mackerel, Rastrelliger Kanagurta, are tropical fish preferring a temperature range of 27-29 degree Celsius. During 1961-1976, the catch of these two fish was predominantly from the southwest coast where the sea surface-temperature ranged between 27.7-28.0 degree Celsius. Oil sardine fishery did not exist before 1976 in the north and along the east coast as the resource was not available."The distributional shifts of these two species, which together contribute 15 percent of the marine fish catch along the Indian coast, are likely to result in considerable changes in species structure and function of the marine ecosystem," said Vivekanandan.

New Indian Express, May 25,  2008