The delectable Hilsa fish is back on the dinning table in Bengal, thanks to a devastating oil spill in Bangladesh last December. It forced the Hilsas to divert their route this year to the Hooghly estuary on the Indian side of Sunderbans for spawning. In local rivers, the fish is being caught in abundance.
According to local fisherman Arjun Mandal, it is a rare phenomenon to see swarms of Hilsa swimming in these local rivers. “Hilsa was missing from Indian Sunderbans for years, and it has come back after a long time,” he said.
For these fishermen, it is like grabbing a fortune with each kilo selling between Rs1,500 and Rs2,500. “An average Hilsa caught there weighs between 500 gms and 1.5 kgs,” Arjun said, adding that it is much more lucrative than having to go to the tiger den in the forest to look for fish and crabs.
Hilsa is a migratory fish that moves from high sea to fresh water during the monsoon period beginning from June and lasting till October. According to Dr Abhijit Mitra, Oceanographer, Department of Marine Science, University of Calcutta, migration of Hilsa is from region of high salinity on the upstream side of rivers.
Because of the oil spill, Hilsa’s diet like Phyto planktons and Zoo planktons vanished from the rivers, forcing the fish to change their course for survival. During the period of spawning, Hilsa goes on a eating binge.
The the oil spill caused by collision of tanker on December 9, 2014, on Sela River has left a thick oil layer over the waters of Passur and Sela. This oil layer about 5 cms thick and spreading across a radius of 60 kms has killed the planktons-major food of Hilsa. “Spreading of oil has hindered the penetration of sunlight through planktons prepare their food,” Dr Mitra said.
As a result, Hilsa have diverted their route from Bangladeshi estuaries and headed towards Indian Sunderban preferably towards Hooghly estuary where salinity is lower than Matla estuary in Indian Sunderbans..
Dr Mitra added that Hilsa are highly sensitive by nature and can gauge the water quality and sense even its slightest deviation due to pollution and other factors. In such a situation they opt for a change in their route for better breeding grounds with low salinity.
“But, unfortunately, overfishing of these migrating Hilsas by the fishermen at such an early stage of their life cycle is jeopardising their growth in population,” said the marine expert.
He added that they are being caught even before they lay eggs and even the fingerlings of Hilsa are not spared. “While on their way back to the sea from their spawning grounds, these juvenile Hilsas are regularly caught and sold in the market as Khoira fish,” they said.