The hilsa production might face serious threat in future for the degradation of the water quality of major rivers like the Padma and Meghna caused by siltation, pollution and sea level rise.
The Bangladesh Fisheries Research Institute’s ongoing research found that the decrease in the depth in the rivers, pollution of their water and intrusion of brackish water for sea level rise are threatening the hilsa production.
In the fishing season in September 2020, the BFRI researchers found no hilsa in the Meghna near Gajaiya and Satnalin in Munshiganj for fall of the water quality of the river water in these regions even though the nation had a record hilsa production of 5.5 lakh tonnes in that year.
BFRI researchers found fall of number of hilsa in the upper part of the Meghna and increase of migration of the fish towards the Padma through Sharaitpur district where the pollution and siltation level of the Padma were lower than that of the Meghna flowing through industrial zones like Munshiganj, Narayanganj and Narshingdi.
‘The hilsa is a hyper sensitive and highly migratory fish. It changes routes very frequently if it senses a little change in its habitat,’ BFRI chief scientific officer Md Anisur Rahman told New Age on Saturday.
‘Water quality samples collected from Gajaria and upstream of the Meghna indicated the existence of high level of contaminators dumped into the river or carried into by the Buriganga and Sitalakhya from the industrial zones of Gazipur, Narshingdi, Dhaka, Narayanganj and Munshiganj,’ Anisur Rahman said.
The depth of the river near Gajaria also decreased due to a huge volume of sedimentation, Rahman said, adding that his recent study revealed that 39 per cent fall in water flow was caused by sedimentation, which led to 26 per cent fall in the landing of hilsa.
But in September 2020, BFRI researchers found hilsa even in the River Mahananda near the Indian border of Chapai Nawabganj following an increase in the flow of the River Padma as India opened the Farakka Barrage.
Between 1997 and 2003, however, no hilsa was found in the Padma.
‘The fish species again started migrating to the river after their production increased by giving protection to the mother hilsa, jatka in the rivers and at the sea,’ Anisur Rahman said.
But, such artificial intervention would not give much benefit in future unless quality of water of the rivers continues to worsen and their depths kept decreasing, said Rahman.
The BFRI data shows that the production of the national fish hilsa dropped down to less than two lakh tonnes during the early years of the 21st century.
After giving protection to mother hilsa fish and jatka for five months in the rivers and in the sea by providing food incentives to the fishermen, hilsa production increased by almost 7.11 per cent in the past one decade.
In 2020-2021 Fiscal Year hilsa production stood at 5.5 lakh tonnes, the BFRI data showed.
The environmentalist, however, demanded the government strictly enforce laws for controlling the production of current nets and river pollution and ensure the navigability of the rivers allowing tides to increase.
The government, they said, must review the development of power plants in the coastal belts as those would have a serious impact on hilsa landing and breeding as the fish migrates towards Bangladesh from the bay through some major rivers located in the Barishal division just for breeding and feeding purposes.
‘The government took suicidal decisions one after another without considering their consequences. Development of so many power plants and the resultant pollution of the river water will force the hilsa to further migrate their routes towards the west which would seriously affect hilsa production in the country,’ Bangladesh Paribesh Andolan general secretary Sharif Jamil said.
Fisheries and livestock minister SM RezaulKarim claimed that the incumbent government initiated continuous and effective programmes under the Hilsa Fisheries Management Action Plan for giving protection to the mother hilsa, spawning and jatka for five months in the sea and in the rivers of Bangladesh.
In the past 11 years since 2009, the fisheries and livestock ministry distributed 3.55 lakh tonnes rice among fishermen in 36 districts only for giving protection and the coverage limit further increased this year, he said.
The government also declared six hilsa sanctuaries in the Padma, Meghna, Kalabadar, Harmanik and Tentulia rivers and increased the period of ban of hilsa netting, said Rezaul Karim.
‘The ministries concerned have also been requested for taking measures to address river pollution, ensuring navigability and mitigate the impact of climate change,’ Rezaul Karim said.
Deputy minister for water resources AKM Enamul Hoque Shameem said that the government under the delta plan would control pollution and bring back navigability to all the rivers.
‘No power plants were developed after conducting the environmental impact assessment,’ Shameem said.
The government, he said, was seriously dealing with the climate change issue and water sharing with India.