What Might You See At the Snorkel Trail?

Dr Malcolm Francis wrote up notes on the ‘Trail’ after a dive around the reef late last year:

The Wellington south coast has a high diversity of seaweeds, and they are one of the most obvious features of the snorkel trail. Entering the water through the narrow cobble-lined channels, a snorkeller is soon flanked by thick beds of waving seaweeds – particularly brown or yellowish kelps. The dark brown flapjack Carpophyllum maschalocarpum forms tangled borders on the rock walls, and on shallow boulders, usually shallower than 2 m. It has oval, flat leathery ‘leaves’ a few centimetres long. Below the flapjack are found the more finely divided fronds of (Carpophyllum flexuosum) and  (Cystophora retroflexa), often rising 1–2 m from the seabed and forming tangled forest thickets. C.f. has broad flat brown leaves whereas C.r. has thin, sinuous yellowish leaves.

Half-way along the reef, occasional clumps of golden brown leathery strap weed (Lessonia variegata) cling tenaciously to the parts of the reef exposed to moderate wave action. On the outermost rocks, the bull kelp (Durvillaea antarctica) holds strongly to the most exposed rocks, just above or just below the sea surface, depending on the tide state. If its not too rough to get close, have a look for the large conical ‘holdfasts’ that attach these plants to the rock – they can withstand huge forces from breaking waves. Look out too for occasional giant kelp (Macrocystis pyrifera) with its long rippled blades each supported by a gas filled float at its base, and the introduced Japanese seaweed wakame (Undaria), recognisable by its broad brown sheets with a flattened mid-rib running the full length of the fronds.

Scattered along the edges of the reef, and on boulders on the bottoms of the channel, you will find mini-forests of emerald green sea rimu (Caulerpa flexilis) with its small spiky rimu-like leaves arranged regularly along the side branches, looking like Norfolk pine trees. A close relative (Caulerpa brownii) has no or very few side branches. Both these seaweeds can form dense green swathes of several square metres. Another relative, sea grapes (Caulerpa geminata) forms smaller patches, usually on the darker steep sides of rocks. This is also where you may find shade-tolerant red seaweeds, of which there are many species in the reserve, each with a different patterns of branching fronds –there are a number of different types to be seen.

A variety of fishes inhabit the snorkel trail. Wrasses skull along with their pectoral fins, always on the move, and will curiously swim in for a look at you, then disappear before coming back for another look. The banded wrasse (Notolabrus fucicola) and the spotty (Notolabrus celidotus) are the commonest wrasses. Large banded wrasse are mainly dark grey with yellowish splotches along the back and on the snout, and they reach about 40 cm; smaller individuals less than about 20 cm may are more cryptically coloured, being brown or green speckled with yellowish spots, a perfect camouflage for blending in with the gold and brown kelps. Spotties are smaller and are always active. Juveniles and females are recognisable from their large black spot in the middle of the body; larger males lack the black spot but often have small black blocks on the upper middle of the back. Blue-grey, oval-bodied blue moki (Latridopsis ciliaris), up to about 30 cm long, may be seen over the cobbles at the bottom of the channel, and if you watch them carefully, you may see them gulp a mouthful of sand and gravel from the seabed before spitting it out again – after extracting small crustaceans and worms to swallow.

High up in the shallow kelp forest, look for slender brown to dark green-grey butterfish (Odax pullus). These herbivorous fish bite pieces out of seaweeds and can melt quickly into the forest if frightened by a snorkeller’s approach. Close to the seabed, particularly over the open cobble areas, small triplefins (cockabullies) establish their territories. The commonest species are the variable triplefin (Forsterygion varium) which has blackish stripe along its side and grows to about 15 cm long, and the much smaller (9 cm) but more abundant common triplefin (Forsterygion lapillum) which is usually found over cobblestones. This species may be sandy coloured with a thin dark stripe along its side, or completely black.

In a small cave halfway along the left of the reef, and about 2–3 m down near the base of the reef, there is a nest of small crayfish (Jasus edwardsii), also called rock lobster, hiding out of the daylight. Also near the base of the reef, look for paua (abalone, Haliotis iris) with their oval shells (often covered in pinkish coralline algae) and black feet clinging strongly to the rocks. They often hide under boulders and in crevices when small, but larger animals may be seen on the tops of rocks. On the cobbles and sand patches at the base of the reef, and in the channels, sea cucumbers (Stichopus mollis) look like large brown slugs as they ingest sand and sediment and extract the organic matter from it. Scattered all over the cobbles are many small (up to 6 cm across) cushion starfish (Patiriella regularis) and you may also see the large predatory yellow-brown 11-armed starfish (Coscinasterias muricata) and the purple 7-armed starfish (Astrostole scabra), the latter can be easily identified by its bright orange tube feet on the undersides of the arms.

Near the entrance from the beach, look for large limpets clinging to the bare rocks near the surface (they may be above water at low tide), where they graze the fine algal film from the rocks. Scattered over many of the brown seaweeds are wandering anemones (Phlyctenactis tuberculosa) – large purplish to light brown, lumpy blobs attached to the fronds. Occasionally you may see a few short tentacles protruding from the top end, but usually these are withdrawn during the day, and come out at night to feed on small animals that bump into them.