Harbour seal on Bull Island. Image: John Fox.
The survey found no change in how seals used the haul-out sites, meaning nearby marine construction had minimal effect on the animals.
Risk monitoring and mitigation by authorities has paid off handsomely for seals in the Dublin Port area, with a survey finding that their population is “healthy and thriving”, despite massive marine construction in the area.
Dublin Port’s Masterplan 2040, adopted in 2012, consists of a number of large-scale marine construction projects to improve the country’s maritime trade, which is expected to grow 27-fold between 1950 and 2040.
As part of its construction work – which involves extensive piling – Dublin Port Company (DPC), the state-owned commercial company behind the massive project, funded a seal survey in Dublin Bay and nearby waters, including along the coast from Sandycove to Bull Island, which has been published in the Royal Irish Academy journal.
The study, which involved surveying 10 seal haul-out sites – mostly with unmanned aerial vehicles – between 30 June 2023 and 18 January 2024 found that the same haul-out sites were consistently used by seals throughout the survey period.
Haul-out sites are important for seals, and enable them to come out of the water to rest, moult, breed and have pups, and according to DPC, a lack of change in haul-out site usage by the seals shows that its mitigation and monitoring efforts are proving to be effective.
The survey found that grey seals were more abundantly present in the area than harbour seals, with the survey counting 326 grey seals in October and 300 in July, while harbour seals peaked at 117 in July.
Moreover, grey seals were recorded on Dalkey, Lambay and St Patrick’s Islands and on Ireland’s Eye, the survey found, while most of the harbour seals were observed at Rush Head, Lambay Island and North Bull Island, with small numbers recorded at Sandycove.
According to Dublin Zoo, Ireland is home to up to 10,000 grey seals, and only about 4,000 harbour seals, which have been declining in population in the country.
“It is great to see a healthy and thriving seal population in Dublin Bay,” said DPC port engineer Eamon McElroy.
“We take our environmental responsibilities seriously and seek to operate in harmony with the Dublin Bay Biosphere. Working with our partners the Irish Whale and Dolphin Group ensures that we responsibly monitor seal populations and can respond to any changes that occur.”
Simon Berrow, the CEO of the Irish Whale and Dolphin Group who co-authored the study said: “We are grateful to Dublin Port not only for implementing strict mitigation measures to ensure there is no impact on local marine mammal populations in Dublin Bay and adjacent waters, but that they support research and innovation which will assist in mitigating similar developments elsewhere as well as contributing to our knowledge base.”
CETUS, or cetacean, elasmobranch, turtle and seabird, is an Irish marine project that is investigating how sensitive marine species such as sharks, seabirds and dolphins might interact with existing and planned offshore renewable energy infrastructure.
Its project manager told SiliconRepublic.com last year that the project is compiling existing datasets on the distribution and abundance of sensitive species, which will allow the researchers to both assess data quality and also identify which areas have limited or no data.
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