The most comprehensive assessment of the state of the seas off Northern Ireland and the rest of the UK has produced a mixed picture.
The work was done by UK scientists, including those from Stormont’s environment ministry.
But most seabird populations, including kittiwakes, puffins and herring gulls, remain at risk.
More information is needed to properly assess the status of species like whales and dolphins.
Marine litter remains a problem and climate change and other human impacts are having an effect.
Scientific officer Helen Hanratty, who helped compile the report, said the information now available was the most comprehensive gathered to date.
It measures improvements and declines in species and habitats against a 2012 baseline.
“Fifty per cent of biodiversity in Northern Ireland is actually below the sea,” she said.
The report was welcomed by the head of the Northern Ireland Environment Agency, David Small.
“It gives us a much better understanding of the state of our seas and what’s in them,” he said.
“It also provides more analysis on the existing and emerging pressures and what more needs to be done to protect our marine environment, prevent its deterioration and restore it, while allowing sustainable use of marine resources.”
The Northern Ireland Marine Taskforce, an umbrella organisation for conservation groups, said the report provided “further evidence of the struggles our seas are facing”.
Spokeswoman Ellen MacMahon said it was crucial that binding ambitious targets for improvements were set.
“Northern Ireland’s marine environment is important for a range of species and habitats, such as harbour porpoise, common skate and seagrass beds, to name a few. Decisive action must be taken to protect and enhance our marine environment.”
Mr Small said the information collected would be used to set “robust and targeted measures” to improve marine protection.
The public have been invited to submit ideas through Northern Ireland’s recently launched environment strategy consultation.