DHAKA (AlertNet) - Fishermen are finding unexpectedly large quantities of Bangladesh's national fish Hilsa in coastal estuaries out of season, a trend scientists believe is caused by the impacts of climate change and pollution on their breeding patterns.
The silvery Hilsa fish, popular for its tasty flesh, normally migrates from the Bay of Bengal into Bangladeshi rivers between June and October, where it breeds.
In winter, fishing communities in the southern coastal district of Barguna often suffer from hunger as the government bans river fishing between November and May to help Hilsa minnows mature. Families struggle to get by, despite receiving financial assistance from the state.
This year is different. Azhar Ali, a trader waiting at Machkhali fishing station for boats to return from the estuaries, explains that Hilsa fish went for 350-400 taka ($5-$6) per kilo in the peak season, but now, unusually for the off season, they are selling for 200-250 taka per kilo because there are so many around.
Naznin Begum, the wife of a Machkhali fisherman, is happy that her husband is getting a good catch at this normally lean time of year, because it gives them the rare assurance of having enough to eat. "Every year in this period, our rice pots remain empty. Children shout for food. But this year we have no such tension (thanks to) God's kindness," she explains.
For the past two weeks, fishing stations in this remote coastal district have been bustling with fishermen and traders. Boats have been returning from the estuaries full of large Hilsa, and traders have been snapping them up for clients in the capital Dhaka and other parts of the country.
Sagir Alam, head of the Patharghata Fish Traders Association, says his members are transporting fish worth 15 million taka (around $211,000) each day. But he admits it's a puzzling situation. "We can't imagine such large Hilsa fish during the winter. But now we are getting fish of 1 to 1.5 kg each. We are little bit mystified."
Scientists say the recent surge in Hilsa fish out of season is one sign of the growing effects of climate change on ocean ecology.
Dr Sultan Mahmud of the fisheries faculty at Patuakhali Science and Technology University explains that rising sea temperatures are disrupting breeding patterns, and are contributing to a shift in the mating and migration of the Hilsa fish.
The Bay of Bengal has four fishing grounds, but recently Hilsa fish have been found outside these zones. Mahmud and his university colleagues plan to launch intensive research on the issue soon.
Climatic variability is affecting the fish's growth and reproductive cycle, according to Mahmud. The large fish being found in estuaries out of season may be coming in from the deep sea for late breeding.
"This is a sign of climatic pressure on the bay. The effect will also put pressure on other sea mammals," he notes, adding that the whole food chain is being impacted.
The Hilsa fish isn't the only species being affected by environmental changes linked to global warming, including more intense monsoon rains and tropical cyclones.
Last October, Olive Ridley turtles on Saint Martin's island laid eggs three months earlier than usual. And, in December, fishermen in the Bay of Bengal caught unusually large volumes of Red Snapper fish over a period of several days.
RIVER ECOSYSTEMS UNDER STRESS
Extreme weather and pollution are compounding the shifts out at sea. The Hilsa fish is losing considerable stretches of its river breeding grounds, as many rivers have changed course and narrowed due to siltation caused by droughts and reduced water flow upstream.
River ecosystems are also being damaged by the dumping and run-off of untreated sewage, fertilisers, pesticides and industrial chemicals.
Fishermen used to catch Hilsa in many Bangladeshi rivers, including the Padma, Jamuna and Meghna. But as many dry up into thin canals during the summer months, the fish can no longer head hundreds of kilometres upstream, which they naturally do to breed.
The building of dams and barrages upstream is also preventing their normal migration, cutting their numbers upstream. The loss of their spawning grounds seems to be driving the fish to breed too early or too late, and in rivers much closer to the sea.
Abdur Rashid, 65, a fisherman in Bishkhali in Borguna district, says he hasn't seen this many Hilsa fish during the winter in the 50 years he has been working.
"Usually, we can't fish in this period as the government doesn't allow us to go to the river. We starve with family members, and struggle to survive," he explains. "This year the scenario is totally different. We are getting a huge volume of Hilsa fish and can earn money to buy food."
Fishermen Md Aslam, Alamgir Sarder and Sagir Hosen agree, saying they would expect to find only young fish at this time of year. For them, what's happening now is a "miracle".
But some worry this new phenomenon could bring trouble. "We may not get adequate Hilsa fish next season," frets fisherman Ahmad Hosen. "I am afraid there may be danger in the offing."
Patuakhali university expert Mahmud echoes his concern. "Getting Hilsa fish in winter is not only astonishing but also alarming," he says. "Climate change could be the knock-out punch for many species which are already under stress from habitat loss."
Syful Islam is a journalist with the Financial Express newspaper in Bangladesh. He can be reached at firstname.lastname@example.org.
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