Fish stocks in the Bay of Bengal are declining at an alarming rate, while jellyfish populations are rapidly increasing, according to findings from a recent deep-sea survey and research programme. The study has also detected plastic pollution at depths of up to 2,000 metres, raising serious concerns about the health of the marine ecosystem.

Despite the worrying trends, researchers have identified 65 previously undocumented aquatic species, highlighting both the richness and vulnerability of Bangladesh’s marine biodiversity.

The findings were presented on Tuesday morning at the state guest house Jamuna, where the survey and research report on marine fisheries resources and the ecosystem of the Bay of Bengal was formally handed over to the government.

Those present at the meeting included Fisheries and Livestock Adviser Farida Akhter, Chief Adviser’s Special Envoy for International Affairs Lutfe Siddiqi, Professor Syedur Rahman Chowdhury of the Institute of Marine Sciences at Chittagong University, and Assistant Director of the Department of Fisheries Dr Md Abdullah Al Mamun.

The survey was conducted aboard the research vessel R V Dr Fridtjof Nansen between August 21 and September 21 last year. A total of 25 scientists from eight countries participated in the month-long expedition, including 13 researchers from Bangladesh.

Presenting the key findings, Prof Syedur Rahman Chowdhury said the excessive growth of jellyfish in deep-sea areas is a clear indicator of ecological imbalance. He attributed the phenomenon largely to overfishing, noting that the reduction of predator fish species has allowed jellyfish populations to expand unchecked.

He described the presence of plastic waste at a depth of two kilometres as “deeply alarming,” warning that pollution has penetrated even the most remote layers of the marine environment.

Comparative analysis with data from a similar survey conducted in 2018 shows a steady decline in large fish species in deep waters, while fish populations in relatively shallow areas are also shrinking at an unsettling pace.

Concerns were also raised over the increasing use of sonar-based targeted fishing. Fisheries Adviser Farida Akhter cautioned that uncontrolled sonar fishing could severely deplete fish stocks in the Bay of Bengal, adding that the government would take a policy decision on the issue.

The study further revealed a strong presence of tuna in Bangladesh’s deep-sea fishing zones and identified a significant fish nursery beneath the Sundarbans region, underscoring the ecological importance of coastal and mangrove-linked marine habitats.

Speaking at the meeting, Chief Adviser Professor Muhammad Yunus said Bangladesh possesses a marine area nearly equal in size to its landmass, yet lacks adequate knowledge about the extent, potential and sustainable use of its ocean resources.

“We have not properly understood what resources we have or how best to utilise them,” he said, stressing the need for extensive research, data-driven planning and supportive policies to harness the blue economy.

Officials also informed the meeting that the United Kingdom’s Royal Navy is in the process of transferring a multi-role hydrographic and oceanographic survey vessel, HMS Enterprise, to the Bangladesh Navy. The vessel is expected to significantly enhance the country’s capacity to map seabed features, sea depth and other critical marine data.

The chief adviser emphasised the importance of strengthening joint marine research initiatives with countries such as Japan, Indonesia and the Maldives. Identifying challenges through collaboration with international experts, he said, could pave the way for new economic opportunities linked to sustainable marine resource management.