Starfish convocation at Long Beach

Safety in numbers

There are many reasons why animals would gather together in groups. It may be for safety, like the moulting Japanese spider crabs in the Oceans DVD, it may be to find a mate and to socialise, or it may be because something tasty has fallen to the ocean floor and everyone wants in on the action.

Starfish convocation at Long Beach
Starfish convocation at Long Beach

Certain creatures, like sea cucumbers, rock lobsters, brittle stars and abalone, are always seen together. Sea stars, however, are usually quite solitary and seem absorbed in their own little world. A dive at Windmill or occasionally at Long Beach may sometimes reveal starfish engaged in huge pile-ons like over-excited school boys. Usually there are mussels involved!

Rock lobsters on the Maori
Rock lobsters on the Maori

Rock lobsters generally congregate in cracks and crevices in the rocky reefs they frequent. Unfortunately this habit of living in close proximity to one another makes them particularly vulnerable to over-exploitation by poachers (and by that I mean anyone who operates without a crayfishing permit, in violation of its terms and conditions, or outside official crayfishing season).

A gas flame nudibranch among strawberry sea anemones at Partridge Point
A gas flame nudibranch among strawberry sea anemones at Partridge Point

Strawberry anemones are gregarious, and live in colonies that cover patches of reefs and wrecks, right down to over 40 metres. Other creatures (such as the nudibranch above) often show little regard for their personal space, and walk right over these tiny pink creatures.

Anemones at Partridge Point
Anemones at Partridge Point

In both the picture above and the one below, you can see the dense congregation of sea cucumbers – more than one different kind – that covers many of the reefs in Cape Town. Even on sandy sea floors, such as around the Cape Matapan, golden sea cucmbers form fields of delicate tentacles protruding from the sand. In terms of biomass, sea cucumbers of all sorts are believed to be among the most prolific creatures in the ocean.

Urchins and sea cucumbers at Partridge Point
Urchins and sea cucumbers at Partridge Point

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Clare

Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

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