Seals in Dublin Bay thriving amidst major port developments

Seals are an integral part of Dublin Bay’s marine biodiversity, frequently observed along the coast from Sandycove to Bull Island and even within the Dublin Port area. Despite large-scale marine construction works currently underway as part of the second phase of Dublin Port’s Masterplan 2040 (MP2), the local seal population remains healthy and thriving, as revealed by a comprehensive new survey. 

The MP2 project involves extensive piling operations at the Port’s easternmost point to construct two new ferry berths. As part of these works, Dublin Port Company funded a major study of seals in Dublin Bay and nearby waters, recently published in the Royal Irish Academy journal Biology and Environment.

Haul-out sites are important for seals in Dublin Bay as it enables them to carry out essential functions such as resting, pupping and moulting. Knowledge of the location and use of these sites is important for conservation management to ensure they remain available and undisturbed during key times of the year.

A total of ten seal haul-out sites were surveyed mostly with unmanned aerial vehicles (UAV). Overall, grey seals were more abundant than harbour seals, with maximum counts of 326 in October and 300 in July. Harbour seal numbers peaked at 117 in July.

Most grey seals were recorded on Dalkey, Lambay and St Patrick’s Islands and on Ireland’s Eye, while most harbour seals were observed at Rush Head, Lambay Island and North Bull Island, with small numbers recorded at Sandycove.

The same haul-out sites were used consistently throughout the survey period and are consistent with previous studies suggesting no changes in the use of haul-out sites has occurred. This is an important finding in view of the extensive work being carried out in Dublin Port and shows the mitigation and monitoring undertaken is proving effective.

This survey made extensive use of UAVs which demonstrated their efficient use for surveys of seal haul-out sites, with minimal disturbance to seals. This technique was recommended as a cost-effective tool for regular monitoring of seals at haul-out sites in the future.

Dublin Port Engineer Eamon McElroy commented: “It is great to see a healthy and thriving seal population in Dublin Bay. 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, CEO Irish Whale and Dolphin Group noted: “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.”