Marine Life at Rottnest Island

Photographs Copyright (C) Adrian Baddeley 2003

Silver Drummer/Buffalo Bream Kyphosus cornelii

These large fish, usually in dense schools of a few dozen fish, will be seen `stampeding' around the reef and in large caves. Sometimes they will swim in circles around you.

Western Footballer Sweep Neatypus obliquus

Friendly, curious and loveable little fish, in groups of a dozen or two, which you will often meet mid-water at the beginning or end of a dive. They zip around like a football team. One of them may follow you around like a lost dog during your dive.

Feeding the Fish

Footballers, and some kinds of wrasse, really love bananas. Try it sometime: just peel the banana and squash a bit of it so they can smell it. Then wait for the footballers to start pecking. (But beware of the mariner's superstition that bananas are bad luck on a boat.)

Crayfish (Western Rock Lobster) Panulirus cygnus

These large crustaceans hide in crevices and ledges during the day. They are quite wary. In the winter months you can sometimes get them to come out and "talk" to you, wiggling their antennae to touch your fingers. They are hunted by manic divers from 15 November to 30 June, so after 15 November no surviving crayfish will come anywhere near a human. You may see crayfish out in the open during a night dive - don't shine a light on them or the nearest octopus will get them.

Scalyfin

These dull coloured damselfish are everywhere when you dive at Rotto, and will often charge at you as you swim past, although they are harmless. They have a little territory on the reef, including a hidey-hole and a little garden of algae for their food supply. They tend the garden, nipping off any other species of algae or coral that try to grow there. They are fearless defenders of their gardens from competitors of all sizes. Watch one go berserk as a school of passing fish tries to have lunch on her lawn.

Nudibranch Chromodoris westraliensis	Nudibranchs mating

Nudibranchs (from the Greek for "nude gills") are snails without shells. They are usually about 2-4 cm long and brightly coloured, so you can often spot them on the reef. This one is the common Western Australian Chromodoris which you will see everywhere unless you are blind. In the first picture, the orange tuft of `branches' on the left are the gills; the two red spikes on the right are the rhinophores - sensory appendages for smell. Just in front of the rhinophores are two tiny eyes (which you can't see without a microscope). This species and most of its relatives eat sponges. Nudibranchs are hermaphrodites, with genitalia always on the right side of the animal towards the front. They can often be seen in sexual embrace. Well, there's nothing else to do...

For more information, visit the amazing Nudibranch page at DiveOz. You can even subscribe to "Australasian Nudibranch News".

Western King Wrasse (male)

King wrasse are ubiquitous on the Rottnest reefs. There is usually one male, large, fat and resplendent in colourful markings, and any number of females, smaller, sleeker, and mostly white. The females stick together and drift over the reef, grazing on algae. The male will swim around above the reef, sticking his snout into anything interesting.

Western Red Rock Cod	Scorpionfish

These fish and their relatives Stonefish have poisonous dorsal fin spines which make an extremely painful wound. The fish are perfectly camouflaged against the reef, usually a dull brown colour, until you shine a light on them, when they show up bright red. It would be easy to sit or kneel on one when you think you are settling down on a patch of bare reef.

Cuttlefish Sepia apama

Cuttlefish are related to squid and octopus. They are predators with a well-developed eye and brain, 10 tentacles, and a siphon and a muscular `skirt' which they can use to swim in any direction. Their blood is based on copper oxide rather than iron oxide so their blood is green and their bodies look coppery under a light. When they feel threatened, they may raise their two middle tentacles in a snake-like gesture, swim forward and backward erratically, and if you are lucky, they will coruscate -- put on a fantastic display of rapidly changing colour on their upper mantle surface, using pigmented buds on their skin. They are just very cool creatures.

Western Blue devil Paraplesiops meleagris

Blue Devils are commonly seen under an overhang or in a corner of a cave. Their skin is a deeply saturated dark blue. They may prop themselves up on the reef by their ventral fins (right) or just float motionless under the overhang (left). They are slow-moving. It is rare to find several together, unless one is a juvenile. Stare at them and they will stare back.

Red-lipped morwongCheilodactylus rubrolabiatus

Moderately large fish which mooch around in caves and algae-covered reefs. Their distinguishing feature is the large rubbery red upper lip. They are shy loners, and are difficult to approach. If you make eye contact with them, they will swim off.

Sergeant Baker Aulopus purpurissatus	Old Wife Enoplosus armatus

Sergeant Bakers are always found sitting on top of a reef looking for prey. They are well camouflaged and immobile, so they are hard to spot. You can get quite close to them. When you are too close, they will generally lift their dorsal fin as a threat gesture (see photo), and if you persist they will abruptly zip off.

"Old Wife" are black and white striped with very striking, bright red eyes. They get their name from the observation that when they are caught on a boat they make grunting, chewing noises like a toothless old person. They are almost always found in pairs, drifting quietly around the darker zones of the reef, solicitously keeping an eye out for each other. When they have been spotted they tend to slow down and hug the reef hoping you will pass. Sometimes you can see a magnificent school of Old Wife cruising past with a bit more confidence.

Common bullseye

Every cave worth the name at Rottnest has a horde of these little brown fish, with their huge eyes set very far forward. They just hang around and never appear to exert themselves, but magically get out of your way as you swim close to them.

Sea stars

Starfish are very common and there are many varieties.

Ascidians (left) and Bryozoans (right)	Bryozoans Adeona grisea	Solitary Ascidian	Colonial ascidians ?Sigillina australis

Ascidians (aka "sea squirts" or tunicates) and bryozoans are both technically classified as animals, but live out their adult lives as sedentary colonies or individuals attached to a fixed surface. In the left picture, the ascidians are the dark blue bell-shaped objects - each bell is an individual animal that traps food that swims/drifts through its siphon. The bryozoans are the pale `lace' network structure in which individuals are very small struts of the lace. At Rottnest there are also black lace-like bryozoans, and there are many different forms of ascidians including things that look like tulips and pieces of plumbing. Here's a short-and-simple natural history of ascidians, a superb guide to ascidians with pictures, and another taxonomy of ascidians with pictures.

Sea Cucumbers

"Vacuum cleaners" that digest the detritus on the bottom and deposit piles of fine sand. Dull brown coloured, slow moving, a foot or two in length. Also known as beche-de-mer or trepang, and considered a delicacy in some cuisines (eeeeuw).

Horseshoe leatherjacket	Blackspot goatfish	White-barred boxfish (male)

There are dozens of species of leatherjackets. They all have the same distinctive mouth, which looks very taut and toothy. They are often seen in male/female pairs or in small groups. They are quite shy.

Goatfish are instantly recognisable by the barbels, or feelers under their chins, which they use to rummage around in the sand for crustaceans.

Boxfish have a very characteristic box-like shape because of the armoured plates that protect their bodies. Their swimming is usually fairly slow and funny-looking - like a clockwork toy.

Cleaner Wrasse (small fish) cleaning a Silver Drummer

common WA urchin Centrostephanus tenuispinus	slate pencil urchin Phyllacanthus irregularis

Common urchins can be seen everywhere at Rottnest, a mass of slender blue spines jutting out of a hole in the top or sides of the reef. The slate pencil urchins (so named because their spines were once used as pencils for slates) are less common, and are usually found in caves or wedged deep in a crevice for protection. Both species wander out at night.

Harlequin fish Othos dentex

Foxfish

Intelligent, wary fish that will be seen snooping around you from a safe distance while you explore a cave. Very difficult to photograph because they are instantly aware that something is pointing at them.

black-throated threefin Helcogramma decurrens	wavy grubfish Parapercis haackei

There are many tiny fish at Rottnest. You will see them zipping around the reef or hiding in the algae. Usually they are spotted only when they move. They are all quite wary of humans. They will perch in one spot for a few seconds, then shoot away at the first sign of danger. They are unbelievably hard to photograph.

Woodward's pomfret

The "blondes" of Rottnest: they make a pretty sight, but are quite brainless. They drift in large schools near the top of the reef.

Rays

Rays of various kinds and sizes are plentiful around Rottnest. The little ones are commonly seen hunting for crustaceans and mostly ignore humans. The larger ones (including bull rays up to 2 metres across) are more shy but are also curious. You may see them off in the distance, or winging past underneath you while you are on the safety stop. It is possible to hand-feed them. They should not be antagonised.

Cowrie Cypraea venusta

Live molluscs are fairly common. On this cowrie you can see, partially retracted, the whitish mantle (underneath) and black proboscis (at right end). Just after this photo, the cowrie `jumped' off the ledge, presumably because it didn't like the flash.

Moonlighter	Red-banded wrasse	Banded sweep

Often swim past, usually loners.

Talma Chelmonops curiosus

Quiet loners. Very triangular shape. Graze the reef with their beak specialised for pecking.

Sea carp

Underwater `cows' that spend all their time munching on weed and are not perturbed by anything.

Wobbegong

A predatory shark with mottled camouflage. Fairly common in caves and ledges at Rottnest. Large ones, up to 2 m long, will occasionally be seen swimming just above the reef.

Wobbies deserve respect and should not be molested. With their large mouth and extremely supple body, they are capable of inflicting a nasty bite, in any direction, in a flash. However, they are quite cool headed and will leave you alone if you leave them alone.

Less common

Port Jackson shark Heterodontus portusjacksoni

Champia stipitata

A newly-described species of algae. The type specimen came from Roe Reef at Rottnest Island. Looks like strings of brightly coloured beads.

Octopus

There are several species of octopus at Rotto. They are quite common, but are not seen very often by divers, because they are good at hiding their lair. The lair can usually be recognised by the household garbage - empty bivalve mollusc shells - scattered around.

Banded cleaner shrimp Stenopus hispidis

Look carefully in crevices in dark caves to find these magnificent fellows.

Lionfish

Tropical species. Likes the warmth under coral plates in shallow waters. Those spines are poisonous.

Long-headed Flathead Leviprora inops

Dusky morwong

A relative of the Redlip Morwong, but much less commonly seen. Very shy.

Batfish

Globefish Diodon nicthemerus

Cute, in an ugly sort of fashion. Usually alone. They like to lurk under small ledges. Slow swimmers. Will tolerate a bit of disturbance from divers but remain wary. There is a huge school of them at the bow of the Swan wreck.

Black banded sea perch Hypoplectroides nigrorubrum

Turtles

Boxfish

Nudibranch Phyllidia ocellata	Nudibranch Halgerda sp.	Nudibranch Halgerda punctata	Nudibranch Chromodoris epicuria

There are plenty of nudibranchs around once you start looking.
Phyllidia ocellata is fairly common but the others are rarer.

Flatworm	Bullomorph Sagaminopteron ornatum

These are not nudibranchs.
Flatworms are faster-moving, flatter, more lithe and less gaudy than nudibranchs. They belong to a completely different phylum (Platyhelminthes). They are flat because they have no blood vessels and their cells are supplied with nutrients and oxygen by diffusion. The species seen by divers are from the order of Polyclad flatworms in the class Turbellaria. They eat corals.

Bullomorphs (bubble shells, order Cephalaspidea) are more closely related to nudibranchs (order Nudibranchia). They belong to the same subclass, Opisthobranchs ('rearward gills') of the gastropods. You can see this particular tiny creature Sagaminopteron ornatum (about 4 mm across) on virtually every light-grey-coloured sponge at Rottnest. Sometimes you come across one midwater, flapping its `wings'.

Breaksea Cod Epinephelides armatus	Chinaman cod Epinephelus rivulatus	Female blue-tailed leatherjacket

Octocoral Plesiastrea versipora

Corals are colonies of individual animals. The individuals have either six-fold or eight-fold symmetry (at the microscopic level). Hexacorals (6-fold symmetry) are the hard-shelled, reef-building corals. Octocorals (8-fold symmetry) tend to be squishier and they are able to live in deeper and colder water.

Plesiastrea versipora is one of only a few stony corals in southern Australia. It is classed as "In Peril" by Reef Watch who request divers to report any sightings.

Colonial Ascidians Sycozoa cerebriformis

Cowrie Cypraea rosalei