June 12, 2017 12:35:46 am
LAST MONTH, an international group of marine biologists submitted a report to the International Whaling Commission, Slovenia, highlighting an alarming rise in the number of whales washing ashore to India’s west coast in the last two years. The report cited 16 instances of whale mortality along the west coast in 2015, followed by 20 in 2016. This was hugely more than in any year between 2001 and 2014, when the number of whale deaths never exceeded four.
From the emaciated look of the carcasses washed ashore in recent years, researchers believe that they were short of food and moved closer to the shores looking for fish. They say the fish population in the sea has reduced drastically due to a sharp decrease in dissolved oxygen in the water. The team that wrote the report included three members of the Konkan Cetacean Research Team (KCRT) besides researchers of James Cook University in Australia, the Terra Marine Research Institute in Bangalore and the Department of Oceanography of the University of Washington in Seattle.
In addition to the beaching incidents, more frequent sightings along the west coast, too, have become a concern. Besides the 16 and 20 whales washed ashore in 2015 and 2016, there were also eight and three live sightings respectively, or a total of 24 and 23 whales reported along the west coast, dead or alive. Between 2001 and 2014, the highest number of whales reported has been four — on three occasions, all 12 washed ashore.
“Besides the deaths, the number of sightings is also worrisome. Whales are now often seen between 20 and 55 metres from the shores of Maharashtra,” said Mihir Sule of KCRT, one of the authors of the report. KCRT has carried out a Sindhudurg Cetacean Project, as part of a Government of India-UN Development Programme study, in three phases since May 2014 to assess the biodiversity of marine mammals along the 121 km Sindhudurg coastline.
Days after the team submitted the report to the international commission on May 9, two halves of the decomposed carcass of a 44-foot Bryde’s whale washed ashore at two different beaches of Mumbai on May 20. Maharashtra has reported the highest number of whales since 2001 — 37, several times more than Gujarat (11), Karnataka (11) and Kerala (9). These include 23 carcasses washed ashore.
“In Maharashtra, seven whales have been stranded since May 2016, of which three were Bryde’s, three were blue whales and one was not identifiable,” the report stated. “The maximum number of carcass reports are of Maharashtra and the species most reported is the Bryde’s whale.”
Vinay Deshmukh, marine biologist and former chief scientist of Central Marine Fisheries Research Institute (CMFRI), explained the possible reason, saying: “The Indian Ocean and the Arabian Sea have great amounts of dissolved oxygen for fish to breathe. However, that has begun to reduce and there are now oxygen minimum zones in the Arabian Sea with low levels of dissolved oxygen for fish to breathe. The fish population has dropped possibly due to this, and this has also probably drawn the whales closer to the shores.”
The report, too, dwelt on the change in fish population. “While exploring fish catch data from the west coast we found that there has been a steep fall not only in the overall catch of commercially imported fish but also an almost 82 per cent drop in sardine (locally called tarli) since 2014,” the report stated.
“It was also stated by CMFRI (Central Marine Fisheries Research Institute) that there was a peak in jellyfish during the time. Such shifts in prey-predator populations are probably causing a cascading effect in the marine food chain… several of the whales washed ashore in Maharashtra in 2015-16 look emaciated and we are concerned that this might be because of low densities of preferred prey.”
Scientists have stressed the need for collaboration among local administrative authorities, the forest department and veterinarians trained in necropsies or dealing with live stranding. “There is no one skilled to perform this right now,” said one scientist.
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