More fish species on the east coast, especially in the waters off Odisha and West Bengal, are highly vulnerable to climate change, according to a first of its kind assessment by the Central Marine Fisheries Research Institute (CMFRI). That vulnerability stems not only from changes in climate but also from fishing pressure and lower productivity.
Overall, 69% of the 68 fish species studied were found to be vulnerable to climatic changes. They include Bombay duck, tuna, sharks, various shrimp, pomfret and catfish, among others. “The west coast also has high fishing pressure but is richer in fish so it is a bit less vulnerable,” said Dr. P. U. Zacharia, CMFRI scientist and lead author of the report. Fish inhabiting surface or near surface waters like tuna, mackerel and sardine are most affected by temperature change; they also account for a sizeable chunk of the catch. Overfishing plays a major role in the vulnerability of 16 species. “Overfishing leads to increased sensitivity to climatic fluctuations,” Zacharia said. Vulnerability hinges on the ability of a species to adapt to climatic change. Their spawning patterns, geographic location and the availability of prey would eventually determine their numbers. Species most under pressure include Bombay duck on the western coast, hilsa in the east and the oil sardines found off Tamil Nadu. For the assessment, the CMFRI studied important fish species in four geographic zones: northwest (comprising Gujarat and Maharashtra), southwest (Goa, Karnataka, and Kerala), southeast (TN and a part of AP), and northeast (northern AP, Odisha and WB). Scientists looked at how exposed each zone was to changes in sea surface temperature, ocean current speed and rainfall. Sea surface temperature rose by between 0.5-0.8°C along the Indian coast since 1975, with the highest increases on the west coast. Fish that inhabit surface or near surface waters are most affected by temperature change. These pelagic fish, as they are called, comprised more than 50% of fish landings in India last year, and include Bombay duck, ribbonfishes, mackerel (bangda), tuna, and sardines (taarli). As important as climatic changes is a species’ sensitivity to those changes and its capacity to adapt to them. The study determined this by looking at biological characteristics of each species — whether it feeds on a variety of prey or has a long spawning season for example — as well as whether its population was already under pressure from fishing. Some like Bombay duck, golden anchovy and hilsa are more vulnerable because they inhabit a limited geographic range. By contrast, fish with a wide geographical distribution like seer-fish (surmai), sardines and lizard-fish may have a higher chance of survival. Others like sharks, catfish, and tuna are vulnerable because they are large, relatively slow-growing and less fecund. These species might find it harder to replenish their populations in a climate change scenario coupled with high fishing pressure. Only a few species are vulnerable mainly due to climate. Shrimp may be one of them — their nurseries are the estuaries, Zacharia notes, which will be directly affected by increased salinity from rising seas. More resilient fish include sardines and mackerel. They have a wide geographic range and also grow and reproduce quickly. But even sardines are vulnerable on the east coast, the study warns, since they are much less abundant in that region and have come under high fishing pressure. The oil sardine catch off Tamil Nadu may not sustain in the long run, Zacharia said. The report recommends tackling overfishing, especially of the most vulnerable species, and preventing further destruction of coastal habitats. Key measures include reducing the number of fishing boats, regulating the catch of juvenile fish, and enforcing bans during breeding seasons. “We can’t do that much to stop climate change in the short term,” said Zacharia, “but we can make exploitation of fish more sustainable.”
(Source: The Times of India, Mumbai, 19 December 2016)