shark eggs on the seabed

Discovery of a shark nursery 200 miles west of Ireland has been described as a ‘rare occurrence’.

David O’Sullivan, INFOMAR and chief scientist on the SeaRover survey (Sensitive Ecosystem Analysis and ROV Exploration of Reef habitat) said the nursery was on a scale not previously documented in Irish waters:

“This discovery shows the significance of documenting sensitive marine habitats and will give us a better understanding of the biology of these beautiful animals and their ecosystem function in Ireland’s Biologically Sensitive Area.”

The announcement was made during the INFOMAR (Geological Survey Ireland and the Marine Institute) seabed mapping seminar where video highlights were debuted.

Koen Verbruggen, GSI Director, said the discovery demonstrated the importance of mapping seabed habitats which help to understand and manage Ireland’s vast and valued ocean resources.

“Our data and team continue to make significant contributions to harnessing our ocean wealth.”

Mermaids’ purses

Very large numbers of egg cases, commonly called mermaids purses, were filmed on the seafloor at depths reaching 750m. Such large concentrations of egg cases are rarely recorded, indicating that females may gather in this area on the seafloor to lay their eggs, the scientists believe.

A large school of Blackmouth catshark (Galeus melastomus), abundant in the northeast Atlantic were present at the site. It is likely the eggs are of this species. A second more unusual and solitary species, the Sailfin roughshark (Oxynotus paradoxus) was also observed.

“Both species are of scientific interest as Ireland has an obligation to monitor deepwater sharks under the Marine Strategy Framework Directive”, explained Maurice Clarke, Fisheries Ecosystem Advisory Services, Marine Institute.

The Sailfin roughshark is listed as ‘Near Threatened’ by the International Union for Conservation of Nature. The species grows to a length of 1.2m and is usually observed moving slowly with deepwater currents, feeding on small benthic invertebrates. The individual may have been feeding on the eggs although this was not observed by the science team.

“No pups were obvious at the site and it is believed that the adult sharks might be utilising degraded coral reef and exposed carbonate rock on which to lay their eggs. A healthy coral reef in the vicinity may act as a refuge for the juvenile shark pups once they hatch.

“It is anticipated that further study of the site will answer some important scientific questions on the biology and ecology of deep-water sharks in Irish waters,” Dave O’Sullivan added.

SACs in Irish waters

The shark nursery was observed within one of six offshore Special Areas of Conservation (SACs) in Irish waters designated under the EU Habitats Directive for Annex 1 reefs.  (The SACs host a diverse range of marine animals including sea fans, sponges, worms, starfish, crustaceans and a variety of fish species.)

Dr Yvonne Leahy, National Parks & Wildlife, said their key objective is to assess, protect and monitor Ireland’s offshore marine biodiversity, to begin management of the marine resource.

“Without knowledge of what lives in our seas, we are at risk of never fully understanding and appreciating Ireland’s marine environment.”

The discovery was made while exploring Ireland’s deep-water coral reef systems in July. The exploration initiative was a collaboration jointly funded by the Irish Government (DAFM & DCHG) and the EU’s European Maritime and Fisheries Fund, supported by Marine Institute, NPWS, Geological Survey Ireland, & NUIGalway.

The INFOMAR Programme is a Government of Ireland initiative, funded by Department of Communications, Climate Action and Environment and is a deliverable under Project 2040, Ireland’s National Development Plan.