Migratory routes and spawning or breeding grounds of hilsa at the Bay of Bengal are being shifted due to pollution, siltation, and climate change, says a recent report of the London-based International Institute for Environment and Development (IIED).
It says hilsa have changed their migratory routes and spawning or breeding grounds in response to physical and chemical changes of the habitats due to pollution, siltation, and climate change impacts.
“If they’ve done so, then the most important hilsa sanctuaries will have to change accordingly. Therefore, careful assessment and regular monitoring of the hilsa migratory routes and breeding grounds is crucial,” according to the report.
Except some biological information collected from some parts of the migratory routes or at certain stages of life cycle, there is no complete information on breeding biology, environmental requirement, foods and feeding ecology and hydrological dynamics, and other key physical and biological information related to hilsa, Prof Dr M Abdul Wahab, an author of the report, told UNB.
He said breeding biology, season, time and place of breeding, triggering factors that influence breeding, fate of eggs and spawn and spent fishes after breeding need to be understood for effective management.
Survival rates of fry and fingerlings, recruitment and abundance of jatka (hilsa fry), nursery grounds and duration they spend in freshwater rivers, time of their descending migration should be ascertained, Prof Wahab said.
About the production of hilsa in Bangladesh, the IIED report tilted, ‘Direct Economic Incentives for Sustainable Fisheries Management,’ says most fish were 1 or 2 years of old prematurely gravid females, which produce lower quantities of eggs and offspring and after the intervention, large hilsa of 2–3 years of age dominated the catch.
Besides, there is anecdotal evidence that the setting up of sanctuaries increased the presence and diversity of other river fishes, especially river catfish Pangasius and Rita.
Aiming to boost hilsa production in the country, the government has already declared hilsa sanctuaries — from Shatnol of Chandpur district to Char Alexander of Laxmipur (100 km of lower Meghna estuary), Madanpur/Char Ilisha to Char Pial in Bhola (90km area of Shahbajpur, a tributary of the Meghna), Bheduria of Bhola to Char Rustam of Patuakhali (nearly 100 km area of the Tetulia River) and the lower Padma River at Shariatpur district, 20 km stretch of the Padma River during March–April while the 40km-stretch of Andharmanik in Kalapara upazila of Patuakhali during November to January.
According to the report, the incentive mechanism can therefore potentially deliver additional ecological and biodiversity co-benefits by protecting fish species with similar breeding and migratory patterns as hilsa.
Prof Wahab, also a teacher of Water Quality and Aquaculture (Department of Fisheries Management) at Bangladesh Agricultural University, said the catch assessment survey under the Fisheries Resource Survey System needs updating, improvement and validation to standardise the hilsa fisheries data and relevant information for better management and conservation.
He said coordination among three countries — Bangladesh, India and Myanmar — should be strengthened so that all management and conservation measures are implemented at the same time following the similar protocol.
“The impacts of incentive-based conservation, mode of intervention, justification of subsidies, equity and social justice, sustainability and benefit-cost of the ongoing Bangladesh government management and conservation programme needs to be evaluated,” the fisheries expert said.
He stressed introducing a scientific study in Bangladesh and other countries within the Bay of Bengal through proper ecological and environmental economics evaluation so that a sustainable management approach is formulated for the world’s unique hilsa.
Source: UNBConnect