Northern Diving

Sheephaven SAC’s Saturday mornings dive was at the Flag Rock on the most northern point of Horn Head. Excellent sea conditions with only the slightest swell produced in-water conditions of over greater than 10 metres horizontally though-out the water column. The dive was conducted in one stick thanks to Kevin Boylan who gave up his dive to act as Dry Coxswain, as he took the helm of Dive Boat Ciara for the run out from Downings.

At a depth of 15m the divers could clearly make out the waiting dive boat on the surface – view the Sheephaven Facebook page videos and photo to get a taste of what was on offer. Marine life was abundant and diverse, in particular the present of Pollock both in shoals and solitary and Wrasse, numerous Brown Crabs, with the occasional Lobster.

The most significant marine observation was the presence of Squid egg sacs, attached in a mop to a lobster pot line, most likely from the Long-finned Squid, with the scientific name Loligo paelei, which is the most abundant squid in the North Atlantic. The Egg sacs were placed there by their mother at this time so that the hatching embryo could take full benefit of the increasing plankton bloom that was observed near the surface.Squid are free-swimming mollusc’s, which are intelligent, predatory, fast growing and have a depressing short sex life – dying shortly after reproducing their offspring.

Females hold their eggs inside the mantle (the main tube-like part of the body), which may contain 50,000 eggs. The eggs are covered in a gelatinous substance and form a mop of egg sacs, each of which may contain as many as 200 hundred embryos and are glued to an item on the seabed, or in the case of this dive the line attached to a lobster pot.

The female continues to form egg mops until all the embryos have been released, then she dies. The male continues to survive for a while longer, until he fertilizers the last of the females and then he also dies. As the males approach the end of their lives they become increasing aggressive towards of each other, with even the sight of an egg mop being produced enough to increase their aggression towards each other and also their pursuit of females.

After all the adults have died the embryos are left to develop on their own and take several weeks to hatch, which is timed to coincide with the increasing plankton production taking place in the upper water column. This location of the Flat Rock is ideal for the hatched squid as it is at a point in which three tides meet and in calm conditions in the late spring or early summer the plankton is concentrated into dense lines clearly visible on the surface.