Fiona McIntosh asked Guido Zsilavecz, Chief Naturalist and co-founder of the Southern Underwater Research Group and author of “Coastal Fishes of the Cape Peninsula and False Bay”, and “Nudibranchs of the Cape Peninsula and False Bay” to identify 6 interesting critters to look out for in the rock pools of the Western Cape.
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The shore line in the Western Cape can often seem forbidding: raggedy rocks washed by stormy seas. But at low tide the sea recedes and rock pools emerge.
These at first glance seem rather deserted, with maybe some kelp or other algae but little else. Spend some time looking into one, however, and you can find a remarkable amount of life; there are fishes, sea urchins, cushion stars and crabs.
Most are quite small, and many are very good at hiding under the smallest of pebbles. If you carefully move their shelters, however, they may sit still long enough for you to have a good look.
Here are a number of interesting creatures which may be found:
The bluntnose klipfish
The bluntnose klipfish (Clinus cottoides). Klipfish is quite difficult to identify properly, as many superficially look the same. If however, you look into any rock pool of the Western Cape, the chances are that the fish you see is a bluntnose klipfish. Aptly named, it has a blunt nose, big eyes, and usually (but not always) a dark spot on the shoulder. While never brilliantly coloured, these klipfish do have interesting patterns which can differ from fish to fish. They tend to be quite tame, and while they do try to hide, once they get used to you they usually stick around.
2. The Nosestripe Klipfish
The nosestripe klipfish (Muraenoclinus dorsalis). Easier to distinguish from other klipfish, the nosestripe is elongated (the scientific name “Muraenoclinus” means “moray-like klipfish”), and has, as the common name suggests, a stripe along the nose, which tends to be white. These fish can be very skittish and are often hard to follow as they dash from one hiding hole to another. What makes them interesting is that they can be found in extremely shallow water – in fact, sometimes they are happy enough in just damp sand under a small rock.
3. Dwarf Cushion Stars
Dwarf cushion stars (Parvalustra exigua). These are common in most rock pools, even shallow ones higher up the shore. They are easily overlooked though: although true sea stars, they do not have “arms” as one normally expect a sea star to have: instead, they are just five-sided disks. Their colouration can be quite variable, and they are often very well camouflaged and barely visible so one usually needs a very calm rock pool to spy them.
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4. The Cape Urchin
Cape urchin (Parechinus angulosus). A common sight in most rockpools, to such an extent one often overlooks them. But there’s one interesting habit that they have: very often they are covered with rubble – shells, bits of kelp, and so on. This is not by chance: in fact, these sea urchins actively cover themselves with such debris as a sun shade! The sea urchin not only has sharp spines: between the spines are flexible arms with a little sucker on the end which they can use to hoist the shells up, thus providing them cover from the harsh sun.
5. The Shore Crab
The shore crab (Cyclograpsus punctatus). These little crabs are often noticed only because their discarded shells litter the shoreline after they have moulted. The live crabs, however, can be quite shy, and usually hide in cracks and under rocks, quite high on the shoreline – so to see one you need to look under small boulders – or look at night when they come out to feed.
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6. The Cowled Nudibranch
The cowled nudibranch (Melibe rosea). Nudibranchs are sea slugs, a group of animals with the most astonishing variety, and which are, next to fish, SCUBA-divers favourite subjects. While not often seen, they do also occur in rock pools, growing to about 4cm in length. The cowled nudibranch is interesting in that it catches its prey – small crustacea – by enveloping them with a large hooded cowl on the head.
In the image there are three cowled nudibranchs – a white one, a yellow one, and right behind the white one, an orange one. Most of the time these do not wander about in the open in rock pools, so it requires a careful look under rocks to find them. If you do they may contract into a small little blob – in which case, just wait, and it will start extending itself as it starts moving. Always keep the specimens in the water while you’re observing them.
To celebrate the imminent arrival of December, we’re giving away 3 copies of Fiona’s book, Dive Sites of South Africa and Mozambique. All you need to do is enter your details below. The competition ends on 30 November 2017.