A “rare” shark nursery of staggering proportions has been spotted deep under the ocean’s surface off the coast of Ireland. Hailed as the biggest discovery of this kind ever made in Irish waters, the enormous shark nursery contains thousands of uncased shark eggs, which seem to belong to the Blackmouth catshark species (Galeus melastomus).

Commonly referred to as “mermaid purses,” the shark eggs were uncovered some 200 miles west of Ireland, hidden 750 meters (2,500 feet) deep beneath the surface. Uncovered during a three-week exploration of the deep-water coral reef systems in Ireland, the shark nursery was found nestled within a large reef — with the eggs laid on dead coral skeletons.

Alongside the massive number of shark eggs, marine biologists also sighted a large school of Blackmouth catsharks swarming above the reef — which prompted them to believe that the eggs were of the same species.

According to the Marine Institute (MI), which participated in the discovery together with the Geological Survey of Ireland, coral reefs can provide refuge for newly born sharks. Which is why finding the shark eggs clinging to the dead coral didn’t necessarily come as a surprise. What astounded the scientists was stumbling upon such a large concentration of shark eggs in the same location — a rare occurrence that suggests that female catsharks might be flocking to this location to lay their eggs on the seafloor.

“No pups were obvious at the site and it is believed that the adult sharks might be utilizing degraded coral reef and exposed carbonate rock on which to lay their eggs,” stated MI officials.

The eggs, which are believed to belong to the catsharks, were laid on the remains of dead coral, which provides a kind of protective carpet, preventing them from being swept away by currents. https://t.co/HCJK0qNzs6 — Wildlife Warriors (@GlobalWarriors) November 10, 2018

This remarkable discovery was made as part of the INFOMAR program — an MI initiative aimed at creating “integrated mapping products of the physical, chemical and biological features of the seabed in the near-shore area,” notes CNet.

The finding was announced last week at the INFOMAR Seabed Mapping Seminar in Kinsale, Ireland, and is the crowning achievement of the SeaRover (Sensitive Ecosystem Analysis and ROV Exploration of Reef habitat) survey — undertaken in July with the help of MI’s remotely operated vehicle (ROV) Holland 1.

“We are delighted to report the discovery of a rare shark nursery on a scale not previously documented in Irish waters,” said David O’Sullivan, INFOMAR researcher and chief scientist on the SeaRover survey. “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.”

As O’Sullivan explained, spotting the massive shark nursery — which was sighted toward the end of the three-week survey — was “a real Eureka moment.”

“It was incredible, real David Attenborough stuff. This is a major biological find and a story of this magnitude would have been on Blue Planet if they’d known about it.”

A second shark species, the Sailfin roughshark (Oxynotus paradoxus), was also encountered at the scene. However, his team believes that this solitary shark — a lone individual found moving slowly through the site — was merely there to forage the egg cases.

The team plans to return to the site next summer during hatching season and hopefully catch a glimpse of the newborn shark pups, reports The Guardian.

“Very, very little is known on a global scale about deep-sea shark nurseries,” said O’Sullivan.

In close proximity to the shark nursery, his team set eyes on a healthy coral reef that could offer the shark pups a place to blend in with the scenery and evade predators.

The SeaRover survey was the second of three planned expeditions into the deep waters of Ireland. Footage captured by the Holland 1 ROV, deployed onboard the ILV Granuaile navigation vessel, was posted on YouTube by the MI and can be seen at the link above.