I really couldn’t believe my eyes when I first dived on the Santa Croce Bank – a seamount rising in the Gulf of Naples, one of the most heavily populated, and polluted, areas in Italy. Instead of being, as expected, barren and polluted, this reef – consisting of several pinnacles rising from a sandy seafloor, was literally covered everywhere in red and yellow sea-fans.
All over, SCORES of egg-cases that nursehound mothers, for some reason, love to leave here: they’re everywhere, singly or clustered in groups of up to 9 eggs, tied mostly on large red seafans but also on discarded fishing lines, usually deeper than 30m. There’s so many of them it’s clear this is a MAJOR breeding area – orders of magnitude higher than any other site we have surveyed so far.
After an initial survey of the area, we proceeded on a preliminary study which lasted a whole week for a total of 15 dives.
We selected as study area an isolated rock at the foot of the main seamount at a depth between 33 and 38 meters, 16m long, and then counted all egg cases laid in this area. Each egg case was inspected: we backlit it with a torchlight to assess its stage of development and then classified it in one of 5 groups: freshly laid, developing, near term, hatched, or old and broken.
The results were stunning: a total of 60 eggs were counted in such a tiny area, almost half of them holding baby sharks at different stages of development and the other were old and empty.
Three feeshly laid eggs were then marked with a coloured ribbon, in order to follow their development in the following months: we know than in aquaria baby nursehounds take around 9 months to hatch, but have no idea what happens at sea.
So what have we learnt from this preliminary survey of this area?
Given that this area is extremely small compared to the overall Bank, where there are scores of areas hosting a similar number of egg cases, the overall number of developing nursehound embryos on the Santa Croce Bank is extremely high. No other breeding area reported by divers within this project matches this area in abundance!
The identification of such a rich breeding ground has important consequences for the management of this species which, given its large zie, patchy distribution and evidence for decline in areas of the Mediterranean, may qualify for Vulnerable status under the IUCN Red List of Endangered Species.
We presented our preliminary work at the European Elasmobranch Association meeting in Plymouth, UK, early this month.
Our sincere thanks to the Save Our Seas Foundation for its generous support and to Bikini Diving Center, Aldo Ferrucci and his rebreathers, which provided precious long working times at those depth, and the association of Italian Dive Training Agencies (A.DI.SUB) who disseminated our project amongst their members.