Amazing Facts about Australian
Marine Fishes
Tony Ayling & Steve Parish Sharks • Rays • Bony fishes & more
Introduction
a fish?
of fishes TONY AYLING
Above: Fishes use their fins in a number of ways — for propulsion, steering and as props when resting on the bottom.
FISHES ALSO HAVE FINS, which are membranes supported by spines or soft rays that are attached to a fish’s tail, back, belly and flanks. Moving ( or undulating ) these fins propels fishes through the water and assists with manoeuvring. Fins can also be used as props ( like a bike stand ) when the fish is resting on the bottom.
FISHES EVOLVED IN THE SEA, and even today all fishes either live in the water or are closely associated with a source of water. Fishes have gills to let them breathe ( or rather, to exchange gases ). Through the fine blood vessels in their gill filaments, fishes remove the carbon dioxide that is generated by muscle activity and body processes as well as absorbing the oxygen that is necessary for fuelling life. A few fishes that live in water with low levels of oxygen, or that make frequent forays onto land, have developed simple lungs to take care of this essential gas exchange.
THE AGNATHANS ( OR JAWLESS FISHES ) are the oldest and most primitive group. Most agnathans died out hundreds of millions of years ago, and the only modern representatives of this group are the scavenging and parasitic hagfishes and lampreys. Most of these strange, eel-like fishes live in deep water and are rarely seen. These rather unsavoury fishes do not have jaws but suck up their food after rasping away at it with their rotating, disc-like mouth. Anything that dies and falls to the ocean floor quickly attracts battalions of hagfishes that waste nothing. There are only five species of jawless fishes found in Australia — the vast majority of fishes belong to the other, more advanced groups.
Above: Most fish have scales. All have gills.
Sharks and rays are different from bony fishes. Sharks and rays have small, tooth-like scales ( called “denticles” ) embedded in their skin. Sharks and rays also have teeth that are buried in their gums ( rather than attached to their jaws ). These teeth are constantly replaced and most sharks have several rows of developing teeth behind their main row, waiting to be used whenever a tooth is broken or dislodged. Sharks and rays are also unusual in that they have the mouths and nostrils on the underside of the head, rather than at the front like most fishes. Male sharks and rays have claspers that are used to grasp females during mating and insert sperm into the female’s body. Cartilaginous fishes all reproduce by internal fertilisation of their eggs and either give birth to live young or lay a few large eggs. There are about 1000 species of sharks and rays worldwide — more than 300 of these are found in Australian waters.
Not all fishes have equal sensitivity in all their senses. For example, fishes that live in the permanent darkness of rivers deep underground are completely blind because light is not part of their world. Improvements in their other senses more than make up for this loss of sight.
Text: Tony Ayling. Uncredited photography: Steve Parish
THE BIGGEST GROUP OF FISHES are the bony fishes in the class Osteichthyes. Most modern fishes fall into this group. They have a bony skeleton, teeth attached to their jaws and a covering of overlapping, round, horny scales. The majority of bony fishes reproduce by external fertilisation of their eggs and have a pelagic larval stage. This means that newly born bony fish survive in open water for a period anywhere between two weeks and twelve months.
RON & VALERIE TAYLOR
Left: Detail of a Humphead Maori Wrasse’s eye. Fishes have a similar eye structure to other vertebrates, but some modifications allow them to see clearly underwater.
Above: Agnathans are the oldest fish group in the world. They live in deep water and are rarely seen in Australia.
THE SECOND MAJOR FISH GROUP is the cartilaginous fishes in the class Chondrichthyes, which includes all the sharks and rays. Unlike the agnathans, all these fishes have jaws ( as anyone who fears sharks is all too aware ), but they are distinctive in having a skeleton that is made out of cartilage — a material that is softer than true bone. Ancestral sharks and rays apparently had bony skeletons, but early in their evolution this was replaced with lighter cartilage to save weight and improve buoyancy control.
Like all vertebrates, fishes have very good senses for detecting what is happening in the world around them. Fishes have excellent eyesight and, like humans, most appear to have good colour vision. Because they live in a low-contrast underwater world, fishes have very high contrast vision and can see much further than divers can underwater. Fishes also have acute hearing, especially in the lower frequencies, as well as sensitive noses and a good sense of touch. Many fishes also have a unique electrical sense that helps them to pick up the faint electrical fields given off by all living things. This helps fish detect animals that they cannot see, smell or hear and is a big advantage in a watery world where visibility is often very limited.
MOST FISHES HAVE SCALES, a sort of flexible overlapping armour, to help protect their skin. Some species have lost these scales and have a tough skin, or else secrete toxins to provide protection. Other fishes have developed a solid armour of bony plates that covers large parts of their bodies — leaving slots or holes for their fins, mouth and gill openings.
PADDY RYAN/ANT PHOTO
THREE GROUPS OF FISHES
Fishes were the first of the vertebrates. Their ancestors were the first animals to develop a firm internal support ( the spine ) to protect the main nerve cord and provide leverage for the more efficient operation of muscles. This gave them an advantage over their soft-bodied or hard-shelled ancestors and led to the successful evolution of animals with backbones and internal skeletons. These primitive early fishes started the successful line that eventually gave rise to amphibians, reptiles, birds, mammals and, later, humans.
TONY AYLING
Introduction
Different types
What is
Scientists are still debating how many species of bony fishes live in the oceans and seas of the world, but the total number is thought to be around 15,500. This number is constantly changing as new species are found and described. Hundreds of new species are being found each year, and it is not yet clear what the final total is likely to be. A staggering 25% of these marine fishes are found in Australian waters, so it is clear that our marine fish fauna is incredibly rich and diverse! From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
Class: Chondrichthyes ( sharks and rays ) Order: Orectolobiformes Family: Rhincodontidae
These small to moderate-sized sharks all spend most of the day resting quietly on the bottom but are more active at night. They all have colour patterns that help to camouflage them against the reef background and are often found sheltering under ledges and in caves.
Whale Sharks ( Rhincodon typus ) are the largest of all living fishes. These harmless filter-feeding giants grow to at least 12.7 m long, but recent tagging studies and catches in the Taiwanese Whale Shark fishery suggest that these mammoth sharks may reach 18–20 m in length and weigh up to 36 tonnes!
Wobbegongs are moderate-sized sharks with a wide, flattened body, a fringe of skin lobes around the front of the head, and a mottled or spotted colour pattern. All these features help them hide as they rest quietly on the bottom and help them get closer to their prey. All wobbegongs have two equal-sized dorsal fins set well back on the body, a short tail with no lower lobe, and an anal fin so close in front of the tail that it forms a forward extension of the tail.
HOW BIG? Three wobbegong species are said to grow to more than 3 m but individuals are rarely seen over 2 m long. The Tasselled Wobbegong ( Eucrossorhinus dasypogon ) is said to reach 3.6 m but all those reliably measured have been less than 1.4 m.
LIKE MOST SHARKS, male wobbegongs bite females during mating ( to keep position ). Unborn wobbegongs feed on unfertilised eggs in the uterus, and females give birth to between 12–36 live young that are 20 cm long when born. DANGEROUS SHARKS? Wobbegongs have sharp teeth and have bitten divers who have speared or annoyed them. Reports of Tasselled Wobbegongs killing people in Papua New Guinea are probably false.
Chondrichthyes
Conservation Watch 1 species in Australia; 1 species worldwide. HABITAT: Tropical seas worldwide, both coastal and oceanic.
LURKING PREDATORS
the FACTS!
MOST WOBBEGONGS have a small home range, spending most of their time in one small patch of reef. They usually have only a few preferred resting places within their range.
Above: Swimming with the largest fish in the sea is a goal for many divers.
In spite of their sedentary habits, wobbegongs are effective predators that have long, sharp teeth and powerful jaws. They feed on a variety of fishes, as well as on crabs, shrimps, rock lobsters and squid. Most prey is apparently sucked into the huge mouth when it strays too close to the well-camouflaged, patiently waiting shark. Video recordings have shown unwary fishes investigating and nibbling on the head lobes of a resting wobbegong before they are suddenly gulped down.
SMALL & SLUGGISH
the FACTS!
GENTLE GIANTS Whale Sharks are unmistakable. Apart from their large size, they have a very wide head, a huge, oval mouth and a pattern of white spots and stripes on a dark, green-brown back. The large first dorsal and smaller second dorsal are set well back toward the extremely large, high tail. The tail base is strengthened with wide caudal keels. As would be expected for a filter-feeding shark, the gill slits of the Whale Shark are enormous.
THE WHALE SHARKS that visit Ningaloo in Western Australia each autumn are mostly immature males. Most large sharks appear to be sexually segregated outside of the breeding season. SATELLITE TAGGING is showing that Whale Sharks make migrations of many thousands of kilometres but the full extent of these movements is not yet known.
Whale Sharks feed on a wide range of organisms, including copepods and other planktonic crustaceans, eggs of corals and fishes, squid, small baitfish and even larger fishes such as small tuna and mackerel. They target concentrations of food, suction-gulping huge mouthfuls 15–20 times each minute, straining engulfed water through their gills and swallowing the trapped food. Between gulps, the sharks force water through their gills to re-oxygenate them. Whale Sharks have been recorded gathering at sites where the mass spawning of fishes and corals occurs. Here Whale Sharks feast on the thick clouds of tiny fish or coral eggs.
All the different species of epaulette shark are very similar in appearance and only differ in details of their colour pattern. They all have a large barbel next to each nostril on the underside of the head, an anal fin that appears to be part of the tail, and a large spiracle ( opening ) behind the eye. Epaulette sharks are active day and night, digging in sand and rubble and nosing under ledges in search of invertebrates and small fishes to eat. These sharks are oviparous, and after mating each year the females lay up to 50 eggs that are left on the bottom to hatch. The egg case is elliptical, about 10 cm long, and it takes approximately 120 days for the young 20 cm shark to develop.
YOUNG EPAULETTE SHARKS look very different from the adults. Their colour slowly changes to the normal adult pattern as they grow.
TONY AYLING
EPAULETTE SHARKS are so sluggish and unafraid that they can often be hand held.
Left: A courting pair of epaulette sharks.
Text: Tony Ayling. Uncredited photography: Steve Parish
RON & VALERIE TAYLOR
Wobbegongs: 7 species in Australia; 8 species worldwide. Epaulette sharks: 4 species in Australia; 12 species worldwide. HABITAT: Rocky and coral reefs in coastal waters.
Class: Chondrichthyes ( sharks and rays ) Order: Orectolobiformes Families: Orectolobidae & Hemiscylliidae
SCIENTISTS HAVE FOUND that tagged Whale Sharks make regular dives to depths of up to 1000 m ( where the water temperature is only 4 °C ). WHALE SHARKS are now being targeted for tourist viewing in many areas around the world, including Ningaloo ( below ), and it is hoped that this niche industry will lead to them being protected from fishing.
VERY LONG-LIVED Recent studies have suggested that the Whale Shark is very long-lived, becoming an adult at around twenty years of age and living for more than 100 years. Whale Sharks migrate long distances around the world and are usually found only with other Whale Sharks of the same sex and size.
RON & VALERIE TAYLOR
Conservation Watch
— the largest fish
RON & VALERIE TAYLOR
& epaulette sharks
Whale Sharks
RON & VALERIE TAYLOR
Chondrichthyes
Wobbegongs
IN THE FEW PLACES where Whale Sharks are caught for food, their numbers have plummeted. Unless protected, they may be threatened with extinction.
Left: Many details about Whale Sharks remain a mystery to science, despite regular contact with humans.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
— typical large sharks
the FACTS! FEMALE SHARKS often have skin up to three times thicker than the skin on males. Such thick skin helps females cope with the “love bites” males give them during courting and mating. MOST WHALER SHARKS are viviparous — the developing young are fed by a yolk-sac placenta while in their mother’s uterus. Pregnancy lasts 9–12 months ( depending on the size of the shark ), with litter sizes of between two and 20 pups. PREGNANT FEMALE SHARKS often migrate to nursery areas away from habitats normally frequented by adult sharks. The females do not feed in these nursery areas and leave once they have given birth. Small sharks are an important prey item for many whaler sharks, and this behaviour ensures they do not accidentally eat their own young. THE BLUE SHARK, found in all the offshore seas of the world, is probably the most abundant shark. More than 5 million Blue Sharks are caught every year in the offshore long-line fishery for tuna.
Most of the typical large sharks that occur worldwide and around Australia are whaler sharks. These sharks are all grey or brown in colour and all look very similar. Many of them are difficult to tell apart without closely examining the shark’s fin shape and tooth structure.
Behind the White Shark, the three sharks that rank highest in the number of human attacks are all large whaler sharks. In order of notoriety, these are the Tiger Shark ( Galeocerdo cuvier ), the Bull Shark ( Carcharhinus leucas ) and the Oceanic Whitetip Shark ( Carcharhinus longimanus ).
WHAT SHARK IS THAT?
the FACTS! THE LARGEST PREDATOR? The Tiger Shark may surpass the White Shark and the Great Hammerhead as the largest of the predatory sharks. All three have maximum confirmed lengths around 6 m, but Tigers up to 7 m have been recorded by reliable observers. Measurements of bites in whale carcases suggest they may grow even longer.
WHAT DO DANGEROUS WHALERS NORMALLY EAT?
In Australia, the majority of the sharks encountered by anglers and boaties are whalers. These sharks include the Bronze Whaler, the Bull Shark, the Sandbar Shark, the Dusky Whaler, the Pigeye Shark, the Silvertip Shark, the Silky Shark, the Common Blacktip Shark, the Grey Reef Shark, the Blacktip Reef Shark, the Blue Shark, the Lemon Shark and the Tiger Shark. Some of these species are easy to identify because they have a distinctive arrangement of black, white or silver fin tips — but many can be identified only by checking the shark’s tooth shape and the position and shape of their fins. For instance, the Bull Shark is almost identical with the more offshore Pigeye Shark. The slight differences are the relative height of the second dorsal fin and differences in the shape of the anal fin. The Bronze Whaler, Dusky Whaler and Silky Shark are all large, dark-coloured sharks with no obvious fin markings. Most large whalers just get lumped under the name “bronzy” by Australians! Top to bottom: Blacktip Reef Shark; Dusky Whaler. Both species belong to the whaler shark family.
SEX AND THE SINGLE SHARK Sharks face some serious problems when it’s time to breed. Unlike bony fishes, sharks rely on internal fertilisation, and the male must insert one of his claspers into the female’s genital opening to transfer sperm. With no hands to hold onto the female, and being practically weightless in a three-dimensional watery world, this is not an easy process. The only way a male can hold on is with his teeth. Male sharks usually bite the female on the flank or pectoral fin prior to mating, then hold on tight. Love bites are an important part of the courtship ritual. Left: A group of whaler sharks cruising just beyond the surf zone.
Text: Tony Ayling. Uncredited photography: Steve Parish
Humans are not part of the normal diet of these dangerous whaler sharks, so what do they usually eat? Tiger Sharks have been likened to swimming garbage bins. These sharks range from close inshore out to the open ocean and will eat anything from crabs to turtles, sea snakes to carrion, and sea birds to other sharks. Anything that dies in the sea is fair game. Tiger Sharks sniff out dead whales and will feast upon the carcass for weeks — no matter how putrid it becomes. Bull Sharks are common in shallow coastal waters ( including harbours and rivers ) and also have a varied diet. They regularly feed on turtles, birds, dolphins, crustaceans, squid and molluscs but prefer other sharks, rays and fishes. As its name suggests, the Oceanic Whitetip lives in the open oceans of the world and rarely strays over the continental shelf. These sharks feed mainly on pelagic fishes and squid, but they will take advantage of other feeding opportunities ( such as dead whales and other carrion ) if they are presented.
BULL SHARKS are common in estuaries and rivers. They are the only sharks that can spend their entire lives in freshwater. A population of these sharks lives in Lake Nicaragua in Central America where they never enter saltwater. HOW DANGEROUS ARE SHARKS? On average, less than one person a year is killed by sharks in Australia. This compares with one death from crocodile attacks, two from bee stings, two from lightning strikes, two from surfboard accidents, nine from scuba diving accidents, 320 from drowning, and 2500 deaths from motor vehicle accidents. Each year more people are killed by domestic pets than are killed by sharks!
HOW DANGEROUS ARE THEY? The majority of sharks are completely harmless if we behave appropriately and treat them sensibly. Hundreds of thousands of Australians spend time in the ocean every year and yet very few attacks occur. Of the worldwide fatalities recorded over the past 100 years ( in the International Shark Attack File ), 63 human deaths have been attributed to the White Shark, 28 to the Tiger Shark, 23 to the Bull Shark, one to the Oceanic Whitetip, and only fifteen more to all other species of shark combined.
SHARK NETS and baited drumlines, which protect beaches in NSW and Qld, kill sharks faster than they can be replaced. The populations of many sharks are declining due to this and other forms of shark fishing.
RON & VALERIE TAYLOR
29 species in Australia; 49 species worldwide. HABITAT: Pelagic or near reefs in tropical and warm temperate regions.
Above, left to right: Tiger Shark; Bull Shark; Oceanic Whitetip. These three large whaler shark species are confirmed man-eaters.
RON & VALERIE TAYLOR
Conservation Watch
LEFT TO RIGHT: RON & VALERIE TAYLOR
Class: Chondrichthyes ( sharks and rays ) Order: Carcharhiniformes Family: Carcharhinidae
RON & VALERIE TAYLOR
SHARK: RON & VALERIE TAYLOR
KILLER OR VICTIM? For each person killed by a shark in Australia, there are more than 10,000 tonnes of sharks and rays killed by us! Worldwide it is estimated that more than 100 million sharks are killed each year in fishing operations. Some shark species now face extinction.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
Chondrichthyes
LEFT TO RIGHT: RON & VALERIE TAYLOR
Chondrichthyes
Whaler sharks
Conservation Watch 5 species in Australia; 22 species worldwide. HABITAT: Sandy bottoms on the continental shelf, usually in the shallows.
— filter-feeding giants
Class: Chondrichthyes ( sharks and rays ) Order: Rajiformes Family: Myliobatidae
Class: Chondrichthyes ( sharks and rays ) Order: Rajiformes Family: Mobulidae
Eagle rays differ from stingrays in having a distinct head and a wider body disc that forms elongated “wings” curving slightly backward. These graceful rays appear to fly through the water by flapping these wings. Both wings rise and fall together in contrast to the opposing waves that move stingrays.
Manta Rays, along with the closely related devil rays, are the giants of the ray clan. These huge filter-feeders often measure 4 m across their outspread wings, and there are reliable records of Mantas over 6 m across. They have no barb on their short, whip-like tails and are harmless to humans.
LIKE STINGRAYS, all eagle rays have at least one venomous, daggerlike spine at the base of the tail. Although these are relatively smaller than stingray barbs, eagle rays should also be treated with caution. DIVERS OCCASIONALLY see schools of over 100 Whitespotted Eagle Rays swimming together — a breathtaking sight with their spotted backs, pure-white bellies, long tails and graceful flight. THE WHITESPOTTED Eagle Ray is found worldwide in tropical and subtropical waters. MISTAKEN IDENTITY? As is the case for many fish groups, the naming of eagle rays is constantly evolving. Scientists suspect that the Southern Eagle Ray is actually the same species as the New Zealand Eagle Ray. If this proves to be the case, its scientific name will change to Myliobatis tenuicaudatus.
Text: Tony Ayling. Uncredited photography: Steve Parish
Of the five species of eagle ray found in Australian waters, only two are common. In tropical waters, the large Whitespotted Eagle Ray ( Aetobatis narinari ) is an extremely active swimmer and only comes down to the bottom to feed on the molluscs that make up the bulk of its diet. This species may grow to a width of more than 3 m and, if the tail is undamaged, can reach an overall length of 9 m. They are often seen in schools swimming near the surface and make regular leaps completely clear of the water, falling back with an impressive splash.
the FACTS! HOW BIG DO MANTAS GET? As with all large sharks and rays, there is some debate about the maximum size of Manta Rays. Reliable records up to 6 m are known, with a 5 m wide individual weighed at 1.4 tonnes. Mantas 9.1 m across have been reported but this probably results from exaggeration by an excited observer — “Wow, it was at least 30 ft across!” Convert this wild estimate to metric and 9.1 m sounds almost official.
Mantas feed on plankton, which is filtered from water forced through the open mouth Above: A Manta Ray uses its cephallic lobes to and out through the huge, distended gill help funnel water into the mouth when feeding. slits by stiff gill rakers in front of the gills. Mantas often feed along current lines where plankton are concentrated and can be seen making repeated vertical rolls through patches of dense plankton. Large Mantas also eat small fishes and have been known to join in shark feeding frenzies on bait fish.
WORKING TOGETHER
HOW MUCH DO WE KNOW ABOUT MANTAS?
Eagle rays gather in the mating season, and several males often cooperate to mate with one female. Some males grasp the female’s fins to slow her down until one male grasps the side of her wing in his mouth and flips around so the pair are belly to belly. The male inserts a clasper in the female’s genital opening and mating takes place for about a minute. Each female may mate with up to four males in quick succession. A year later, two to four pups ( each about 20–30 cm across ) are born.
It is very difficult to study large, rare animals like Manta Rays. They are difficult to collect, and there is the moral issue of killing such a huge, long-lived and beautiful creature just so we can get a small amount of data. Modern benign research techniques ( such as tissue probes, satellite tags and photo identification files ) have recently been applied to Mantas as well as large sharks, turtles, whales and dolphins. A few details are emerging on Manta ecology but we still have a long way to go. Mantas are found throughout tropical and warm temperate regions but appear to have a limited migration range in most areas.
Above: Male eagle rays often work together to mate with females.
4 species in Australia; about 10 species worldwide. HABITAT: Open water, usually over the continental shelf but also oceanic.
Manta Rays are all wings and mouth. The hugely expanded, swept-back pectoral fin wings dominate the body, with a thin, almost invisible tail hanging off the back and a very wide mouth set on the front of the head. Long, rounded flaps ( known as “cephalic lobes” ), which are forward extensions of the pectoral fins, protrude from the front of the head on each side of the mouth. These flaps help to funnel water into the Manta’s gaping mouth when it is feeding. In order to reduce drag, these flaps are furled ( like a flag ) to form a straight horn when not in use.
RON & VALERIE TAYLOR
The Southern Eagle Ray ( Myliobatis australis, above inset ) is found from southern Queensland to just north of Perth. The behaviour of this species is very different to its tropical relative, and these rays spend most of the time resting on the bottom. They feed mainly on molluscs, which are crushed with their powerful plate-like teeth. The meat is carefully separated from the shell fragments before it is swallowed. Eagle rays leave piles of shell fragments in their preferred feeding spots!
Above: Unlike undulating stingrays, eagle rays “fly” through the water.
BOB HALSTEAD/OCEANWIDE IMAGES
AN EAGLE RAY feeding in the sand uses its snout and the beats of its wings to dig a hole. Sand is cleared away by blowing water through the mouth and gill slits to expose the molluscs, sea urchins and worms that the ray crushes and eats. A feeding ray is soon hidden from view in a sand storm of its own making.
Conservation Watch
HARMLESS PLANKTON-FEEDERS
ACTIVE SWIMMERS
the FACTS!
Chondrichthyes
— graceful undersea fliers
Manta Rays
Right: Manta Rays are difficult to study, despite being one of the largest fishes in the sea.
THERE ARE HARPOON fisheries for Manta Rays in a number of regions ( such as the Philippines, Indonesia, India, Sri Lanka and Africa ), and in these areas catches are declining dramatically as numbers are reduced. The Manta Ray is listed as threatened on the World Conservation Union ( IUCN ) Red List. MANTA RAYS usually give birth to a single pup every two years. The pups are about 1.3 m across at birth! ALTHOUGH MANTAS are capable of crossing oceans, studies suggest they rarely do. Many areas have small resident populations. In other locations, Mantas make regular seasonal migrations between preferred feeding sites.
RON & VALERIE TAYLOR
Chondrichthyes
Eagle rays
HOW LONG DO MANTAS LIVE? We do not know for sure, but they may live for at least twenty years. Females mature at about ten years when they are 4–4.5 m across.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
62 species in Australia; 150–200 species worldwide. HABITAT: Usually in holes on coral or rocky reefs.
Class: Osteichthyes ( bony fishes ) Order: Anguilliformes Family: Muraenidae
Class: Osteichthyes ( bony fishes ) Order: Anguilliformes Family: Ophichthidae
With their strong, muscular bodies, staring eyes and large mouths full of long, needle-sharp teeth, moray eels are fearsome-looking creatures. During the day, moray eels are usually found with their heads poking from holes, cracks or caves in rocky or coral reefs, but they often emerge to hunt at night.
Snake eels are predatory eels that have adapted to living in sand. A snake eel’s tail makes up more than half its body and has a finless, hard-pointed tip that enables the eel to burrow rapidly backward into sand or mud. The head is similarly shaped so these eels can “swim” forward or backward through the sand!
COUCH POTATO
the FACTS!
All eels are lurking predators that use their sinuous shape to hunt in reef cracks that cannot be reached by other hunters. Moray eels have no scales, but have tough, mucus-covered skin. A single, continuous fin runs from behind the head, around the tail and up the underside of the body. Eels move by passing undulations down their body, a method that is not very rapid or efficient compared with normal fish swimming. Morays have a gill opening that has been reduced to a small hole on the side of the body ( behind the head ) and must constantly open and close the Above: During the day, morays can be seen with their heads poking from holes in the reef. mouth to pump water over the gills. They come out at night to forage. Because morays have a very sedentary lifestyle — the ultimate couch potato! — they have low oxygen requirements and small gills. Although morays will feed during the day, they hunt mainly at night and eat a variety of fishes, octopus, squid, crabs and shrimps. Food is swallowed whole, but large items may be broken up by passing a tight knot down the body.
HOW BIG ARE MORAY EELS? Moray eels range in size as adults from less than 20 cm for some dwarf morays to more than 2.5 m for the Giant Moray ( Gymnothorax javanicus ). SOME MORAYS change colour as they grow. The beautiful Ribbon Eel ( Rhinomuraena quaesita ) is black with a yellow dorsal fin when young, but changes to bright blue with a yellow fin when it matures as a male. It then changes colour to a yellow body with white fins when it changes sex to become a female. THE SPECTACULAR Ribbon Eel ( below ) appears to mimic a harmless filter-feeding ascidian. Unwary fishes may not realise it is a predatory eel until it is too late!
Text: Tony Ayling. Uncredited photography: Steve Parish
Osteichthyes 43 species in Australia; 250+ species worldwide. HABITAT: Burrowing in sand in tropical and temperate regions.
the FACTS!
Snake eels are rarely seen. They usually spend daylight hours buried in the sand with just their eyes and the tip of the snout showing. The firm body is almost round in cross-section and the long, low dorsal and anal fins end well short of the tip of the tail. Snake eels have a larger gill opening than moray eels, and they also have a pair of small pectoral fins that are absent in morays. They have smooth, tough skin ( with no scales ) and a large mouth with an array of needle-sharp teeth. Most of the many snake eel species have a pattern of brown, yellow or orange spots or stripes. The few temperate species are more uniform in colour.
THE SERPENT EEL, found around southern Australia and growing to a length of 2.5 m, is one of the world’s longest eel species. ARE SNAKE EELS DANGEROUS? A fully grown Serpent Eel is a very powerful animal with large jaws and sharp teeth and should be treated with caution. However, they are not usually aggressive. A FEW SPECIES OF BOLDLY black-and-white striped snake eel are often seen swimming in the open during the day ( below ). It is thought that these snake eels are mimicking sea snakes in order to protect themselves from predation.
WHERE DO SNAKE EELS LIVE? Because they are seldom seen, we know very little about snake eels, and many species are known from only one or two specimens. Most species are less than 1 m long when fully grown. Only a few species live in temperate waters, including the Shorthead Worm Eel ( Scolecenchelys breviceps ) that is found in estuaries around southern Australia and New Zealand. Most snake eels are found in tropical waters, around coral reefs and seagrass beds, or over offshore sandy bottoms.
RON & VALERIE TAYLOR
Right: A Starry Moray ventures from its lair.
RON & VALERIE TAYLOR
RON & VALERIE TAYLOR
ARE MORAY EELS DANGEROUS? Morays have powerful jaws full of sharp teeth and can inflict a severe bite if they are provoked or excited. Morays are not usually aggressive, but some attacks have inflicted serious injuries. No fatalities have been recorded.
Conservation Watch
SECRETIVE LIFESTYLE
IS THAT A MALE OR A FEMALE? Moray eels have several different mating systems. Some species are gonochoristic ( individuals are either male or female and stay the same sex through their adult life ). A few morays are simultaneous hermaphrodites ( each individual is both a male and a female ), but most morays are protandric hermaphrodites that mature first as a male and then later change sex to become a female. Courting morays gape their mouths at each other, then entwine their bodies before releasing eggs and sperm that fertilise in the water and drift off as part of the plankton.
Above: Snake eels are usually well buried in sand or mud and are rarely seen during the day.
GARDEN EELS belong to the same fish group as snake eels and are closely related to conger eels. Garden eels live permanently in burrows in sandy areas, usually in large colonies. They are plankton-feeders, stretching up from their burrows like a forest of question marks ( left ), bobbing and weaving as they pluck individual plankton from the water. When danger approaches, they withdraw slowly into the sand until they are completely hidden in their burrows. Garden eels are usually found on sand patches around reefs in tropical seas and several species are found around northern Australia. They are long and thin ( 40–80 cm ), with large eyes near the tip of the snout.
TONY AYLING
Conservation Watch
— reversing sand-burrowers
RON & VALERIE TAYLOR
— needle-toothed hunters
Snake eels
RON & VALERIE TAYLOR
Osteichthyes
Moray eels
LITTLE IS KNOWN about snake eel breeding. It is thought that they release eggs and sperm into the water and have a leptocephalus larval form with a long larval life like other eels. Unfortunately few details are available.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
Conservation Watch 92 species in Australia; about 270 species worldwide. HABITAT: Bottom-living in shallow water on all bottom types.
the FACTS! FEMALE PIPEFISHES and seahorses are usually more colourful than the males. They also initiate courtship — an unusual trait in fishes. THE LARGEST PIPEFISH is the 65 cm long Brushtail Pipefish ( Leptoichthys fistularius ). This species lives in seagrass meadows around southern Australia. A FEW PIPEFISHES, including the tiny Braun’s Pughead Pipefish ( Bulbonaricus brauni ), have no fins and move along the bottom like snakes. MOST OF THE brightly coloured flagtail pipefishes get some of their food by cleaning parasites off other fishes. IT IS THE MALE pipefishes and seadragons that get pregnant! Females lay their eggs in the male’s brood pouch, or stick them into spongy skin on the underside of his abdomen ( below ). The “pregnancy” lasts 3–8 weeks and the young are born as miniature versions of the adults.
— tube-nosed & seldom seen
— armoured plankton-slurpers
Class: Osteichthyes ( bony fishes ) Order: Syngnathiformes Family: Syngnathidae
Class: Osteichthyes ( bony fishes ) Order: Syngnathiformes Family: Syngnathidae
The family name of the pipefishes and seahorses, Syngnathidae, means “fused jaw” and refers to the long, tubular jaw with the tiny, terminal, trapdoor mouth. These fishes are all small and secretive, with elongate, stiff bodies armoured with bony plates and rings.
Seahorses have an arched neck and an elongate, downward-facing head and are named for their resemblance to a miniature horse. They have a large belly and a long prehensile tail that they curl tightly around bottom growths to anchor themselves against currents and tides. All seahorses are very well camouflaged.
SYNGNATHIDAE GROUPS There are four groups in this family. The biggest group is the true pipefishes with about 235 species worldwide. The flagtail pipefishes include about 22 colourful tropical species ( with distinctive fan-like tails ) that swim more actively above the bottom. The third group includes the spectacular seadragons and the prehensile-tailed pipehorses that resemble a cross between a pipefish and a seahorse. Finally, there are the amazing seahorses.
SPECTACULAR SEADRAGONS The endemic seadragons of southern Australia are the most spectacular of the pipefishes. The Common Seadragon ( Phyllopteryx taeniolatus ), with its simple, paddle-shaped skin appendages, grows to about 45 cm long and is brightly coloured in purple and yellow. Males brood 250–300 eggs during the summer months, and these are embedded in soft skin under the tail. Leafy Seadragons ( Phycodurus eques , above ) have many branched, leafy skin growths that camouflage them perfectly among seaweeds, making them very hard to find. Many divers rate seeing a Leafy Seadragon as the highlight of any dive.
GHOSTPIPEFISHES are close relatives of the pipefishes and seahorses that are included in the family Solenostomidae. They have a tubed mouth similar to the true pipefishes but have much larger, fan-like fins. Their skin is densely covered in filamentous skin growths that help to camouflage them against the bottom. Male ghostpipefishes are about half the size of females and have smaller fins. When it comes to parental duties, it is the large females that brood the eggs. They enclose them in a pouch formed by hooking together their large pelvic fins. Right: Male Ornate Ghostpipefish ( at left of picture ) are much smaller than the females.
Text: Tony Ayling. Uncredited photography: Steve Parish
LOCAL CAMOUFLAGE Seahorses can change their colour to blend in with their chosen home, and many species are covered by filamentous skin growths to make their camouflage more effective. They normally rest in a vertical position but turn more horizontally when they want to move some distance, using undulations of the dorsal fin to swim. Pectoral fin beats also help with movement. These fishes swim very slowly and they must rely on camouflage to avoid predators. Above: Seahorses can change colour to blend in However, their armoured body is no with their surroundings. deterrent for a large predatory fish that sees through their disguise; a determined predator simply swallows the seahorse whole. Most species look similar — small differences in shape and spine arrangement are the only distinguishing features. Each species is limited to a relatively short stretch of coastline of only 1000–2000 km. Adults usually range from 10–15 cm in size.
MALE BROODING POUCH Seahorses have a more enclosed brood pouch than the pipefishes. Male seahorses have a distensible sack on their abdomen with a round opening at the top, which can be closed ( right ). During the breeding season, males inflate their pouches to convince females that they would make a good “mother”. A receptive female approaches the male of her choice and raises her head to acknowledge his success. She then uses a tubular ovipositor to lay up to 300 eggs in the male’s pouch. Sperm is waiting in the pouch to fertilise the eggs, which then take about 25 days to develop. Tiny seahorses emerge from the pouch over a period of a few hours. In many species, the young immediately swim up to the surface ( to start a brief pelagic phase ), but others begin life immediately on the bottom near their parents.
Osteichthyes
Seahorses
RON & VALERIE TAYLOR
Osteichthyes Above: Pipefishes are able to conceal themselves perfectly in weedy habitats.
Pipefishes
Conservation Watch 28 species in Australia; about 60 species worldwide. HABITAT: Bottom-living in shallow water on all bottom types.
the FACTS! THE POTBELLY SEAHORSE ( Hippocampus bleekeri ) is common around Victoria, Tasmania and South Australia. It is the largest of the seahorses, growing to a height of 35 cm. IN RECENT YEARS several species of brightly coloured, tiny seahorses have been found clinging to soft corals and gorgonians in tropical waters. These pygmy seahorses grow to a height of only 2.5 cm and are so small and well camouflaged that they are almost impossible to see. Two species are known to occur in Australia and it is highly likely that more await discovery. YOUNG SEAHORSES in their pelagic phase are often found clinging to floating bits of seaweed and seagrass with their prehensile tails. Sometimes dozens of tiny seahorses anchor themselves to a single small piece of weed. If there is nothing better, they will cling to each other. HOW MANY SPECIES? Many seahorse species are very similar in appearance, and fish taxonomists are still not sure how many species there are. New species are being described frequently and an overview of the whole family is urgently needed. It is important to know the total number of species in order to protect these creatures. Many seahorses are collected for the aquarium trade and for use in traditional medicine.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
— bewitching babies Class: Osteichthyes ( bony fishes ) Order: Perciformes Family: Ephippidae
Above: A school of small Longfin Batfishes.
— coral-picking beauties Class: Osteichthyes ( bony fishes ) Order: Perciformes Family: Chaetodontidae
With their large plate-like bodies and spectacular juvenile colour patterns, batfishes are an unmistakable group of fishes. Changes in colour, body shape, fin height and fin shape as an individual fish grows are more pronounced in batfishes than in any other group of fishes.
Conservation Watch 8 species in Australia; 12 species worldwide. HABITAT: Coral reefs.
the FACTS! BATFISHES range in length from 40–60 cm as adults and are nearly as high as they are long.
When most people think of tropical seas, visions of these beautiful, brightly coloured fishes flitting among coral gardens spring to mind. Butterflyfishes are almost symbolic of coral reefs. Although these small fishes are a convenient bite-size for most predators, they happily swim around in the open during daylight hours.
SPINY PROTECTION
Left: With their black and orange colours, young Longfin Batfishes mimic toxic flatworms.
RECENT STUDIES have shown that batfishes eat a remarkable amount of large seaweeds on fringing reefs. Scientists have speculated that batfish-grazing may remove algae on degraded reefs and allow corals to re-establish.
RON & VALERIE TAYLOR
RON & VALERIE TAYLOR
Below: Juvenile Roundface Batfishes have extremely long fins that become rounder and more proportioned as they age.
YOUNG ROUNDFACE BATFISH often have an extended pelagic life, and juveniles aggregate under havens of floating seaweed.
YOUNG MIMICS RON & VALERIE TAYLOR
BATFISHES DO NOT change sex but scientists know very little else about their breeding habits.
RON & VALERIE TAYLOR
Both young and adult batfishes are rarely seen feeding during the day, and it may be that they feed at night or during dawn and dusk periods. These fishes have small, brush-like, three-pronged teeth and feed on a variety of food items. These include sea jellies and other gelatinous plankton animals, benthic invertebrates
Text: Tony Ayling. Uncredited photography: Steve Parish
and seaweeds. They will also eat prawns, crabs and small fishes when possible. Batfishes had a reputation for hanging around under moored boats and eating unsavoury items flushed from toilets, but boats fitted with holding tanks have put a stop to that! Adult batfishes are often seen in tightly packed schools during the day and are frequently curious and unafraid around divers.
RON & VALERIE TAYLOR
STRANGE FEEDING HABITS
RON & VALERIE TAYLOR
Batfishes have a round, laterally compressed body, a blunt forehead and a relatively small mouth. Young juveniles have long, flowing dorsal, anal and pelvic fins that are up to twice as long as the body. These fins shrink in relative size as the fishes grow. In adults these fins are only about a third of the size of the fish’s body. Adult batfishes are rather similar in appearance and colour pattern, but the young fishes gain some predation protection by mimicking a variety of inedible objects and are all dramatically different. Young Longfin Batfish ( Platax pinnatus ) live on coral reefs and are black with a bright orange border to mimic toxic flatworms. Young Round Batfish ( Platax orbicularis ) live in inshore areas and mimic dead leaves in shape, colour and behaviour.
JUVENILE HUMPHEAD BATFISH ( Platax batavianus, below ) mimic feather star arms and often hide close to feather stars.
Osteichthyes
Butterflyfishes
RON & VALERIE TAYLOR
RON & VALERIE TAYLOR
Osteichthyes
Batfishes
Above, top to bottom: Blackback Butterflyfish; Ornate Butterflyfish; Meyer’s Butterflyfish. There are more than 50 butterflyfish species in Australian waters. However, because many species feed on coral mucus, these fish are at the mercy of natural disasters that kill coral ( such as coral bleaching and Crown-of-Thorns Sea Star outbreaks ).
These bright jewels of the reef have disc-shaped bodies, and each species has a different bright-coloured, high-contrast colour pattern. Butterflyfishes have strong bones and solid, sharp dorsal, anal and pelvic fin spines. If a predator comes too close, these fishes erect their spines in a warning that suggests they would make a difficult and dangerous mouthful. Their bright poster colours help advertise this. Many butterflyfishes feed only on coral mucus, which is scraped from the surface of living corals with fine, comb-like teeth. This normally gives them easy access to a huge food resource, but resident butterflyfishes are doomed if most of the corals on a reef die from coral bleaching or Crown-of-Thorns Sea Star grazing.
PAIRED FOR LIFE Most butterflyfishes live in permanent male–female pairs that travel and feed close together and are usually less than 1 m apart! These pairs spawn together most days during the spring and summer breeding season — either at first light in the morning or just after sunset in the evening. Courting couples swim a short distance up off the bottom and release small clouds of eggs and sperm that fertilise and drift off with the current. The developing larvae spend about 40 days in the pelagic environment before they seek out a reef on which to live. If larvae do not find a reef at the proper time, they can delay settlement for several weeks.
Top: Saddle Butterflyfish Above, inset : Longnose Butterflyfish
Conservation Watch 54 species in Australia; about 130 species worldwide. HABITAT: Coral reefs.
the FACTS! BUTTERFLYFISHES are usually small, growing to a length of 10–20 cm as adults. Like humans, once they reach adult size they stop growing. A RECENT STUDY using chemical tags on young Vagabond Butterflyfish ( Chaetodon vagabundus ) on a single small reef found that 60% of the larvae that settled on that reef 40 days later were the offspring of local adults. HOW FAR DO PELAGIC LARVAE TRAVEL? Although many larvae make it back to their home reef, others travel thousands of kilometres during their month-long pelagic phase. This lets them colonise reefs far away. PENNANTFISHES are an unusual chaetodontid group including six species in the genus Heniochus that have a prominent pennant on the front of their dorsal fin. THE WESTERN TALMA is Australia’s only temperate butterflyfish species.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
Hawkfishes
— colourful clowns
— on the lookout
Above: Pink Anemonefish
Class: Osteichthyes ( bony fishes ) Order: Perciformes Family: Pomacentridae
Class: Osteichthyes ( bony fishes ) Order: Perciformes Family: Cirrhitidae
Conservation Watch
Anemonefishes are a specialised subfamily of damselfishes that have adapted to a unique lifestyle. Anemonefishes have distinctive colour patterns and gain protection from predators by living nestled among the stinging tentacles of large coral reef anemones.
Hawkfishes are small, bottom-living coral reef fishes that spend most of their time perched on a conspicuous lookout point in their territory. These colourful fishes have distinctive clusters of cirri on the tip of each dorsal fin spine, which look a lot like pom-poms.
13 species in Australia; about 30 species worldwide. HABITAT: Coral reefs.
the FACTS!
IN RECENT YEARS large numbers of anemonefishes have been successfully raised from fertilised eggs obtained from captive females using aquaculture techniques. This has reduced the collecting of wild individuals. THE THREESPOT HUMBUG ( Dascyllus trimaculatus ) often shares anemone protection with the true anemonefishes. This fish doesn’t touch the anemone tentacles, but hovers close above it. As it grows larger, it strays further from the anemone. MOST ANEMONEFISHES are less than 12 cm long but the Spine-cheek Clownfish ( Premnas biaculeatus ) grows to a maximum length of about 16 cm.
QUEEN OF THE CLAN
Anemonefishes constantly rub the anemone’s mucus all over their skin so that the anemone thinks the fish is just another part of itself. Anemonefishes only venture from their home anemone to graze on nearby algae or feed on plankton close above the anemone.
Because of their restricted habitat, anemonefishes have an unusual breeding arrangement. Each anemone is usually home to a pair of adults and several smaller, immature individuals. The largest adult is always the female, and she is in charge of her mate and the smaller fishes. As long as the adults are alive, the smaller fishes will not grow or become mature. If the large female dies or is eaten, the male of the pair immediately becomes the female and grows. The largest of the immature fish also begins to grow rapidly, quickly becoming a mature male. In spring and summer the female lays several batches of eggs close to the edge of her anemone. The parents guard these eggs until they hatch ( about a week later ).
One disadvantage of the anemonefish’s way of life is that its habitat is severely limited. Each species of anemonefish can live among only one or two anemone species and must find the right species before they can settle. Because of their limited distribution, they often show colour variations from one region to another. Below: Clown Anemonefish Below, inset: Pink Anemonefish
Above: Ringeye Hawkfish
Conservation Watch 12 species in Australia; 35 species worldwide. HABITAT: Bottom-living on coral reefs.
the FACTS! Above: Longnose Hawkfish
ADAPTED FOR LYING ABOUT Hawkfishes live a mainly solitary lifestyle and guard a territory from other fish of their species. Males sometimes maintain a loose, harem-like control over several neighbouring female territories but spend most of the time in their own home. Hawkfishes have elongate, thickened rays on their pelvic and pectoral fins, which are used to prop themselves upright when resting among the coral. Within its territory, each hawkfish has several preferred lookouts on high coral colonies. Here they keep watch for shrimps and small fishes that make up their diet. A few hawkfishes have adapted to life in the turbulent surge zone of the wave-battered reef front. These species are more robust and have a broad sloping forehead and angled pectoral fins. The wave surge deflects upward from forehead and fins, forcing the resting fish firmly against the bottom, helping to maintain its perch. When the surge reverses direction, these fishes quickly spin around so they are once again facing into the racing water. Left: A Splendid Hawkfish using its strong pectoral fins to “perch” on coral.
Below: Saddleback Anemonefish with eggs ( on right ).
MORE SEX-CHANGE ARTISTS Hawkfishes are protogynous hermaphrodites, starting life as a female and later changing sex to become a male. Males seek out their females every evening during the spring breeding season, either meeting them in the female’s territory or in an adjacent neutral patch of reef. After the male’s courting displays excite the female enough, the couple rise up a few metres into open water and spawn small puffs of eggs and sperm that mingle, drift off with the current and begin an extended larval life. Most hawkfishes are widely distributed throughout the Indo-Pacific.
LEFT & RIGHT: RON & VALERIE TAYLOR
TONY AYLING
SINCE THE RELEASE of the film Finding Nemo, Eastern Clown Anemonefish ( Amphiprion percula, below ) have been highly sought by fish collectors. This species was never common but they have now become rare in many localities.
Large anemones use the venomous nematocysts ( stinging cells ) on their tentacles to trap and immobilise the planktonic animals and small fishes that they feed on. How can anemonefishes nestle among these stinging tentacles without being stung? The answer is simple — anemones do not sting themselves if one tentacle brushes against another, because they recognise the other tentacle from the layer of mucus on it.
RON & VALERIE TAYLOR
HOW DO THEY LIVE?
Text: Tony Ayling. Uncredited photography: Steve Parish
Osteichthyes
Osteichthyes
Anemonefishes
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
THE LYRETAIL HAWKFISH ( Cyprinocirrhites polyactis ) has adopted a more open water lifestyle, living in groups that feed on planktonic crustaceans, and looking and behaving very much like a fairy basslet. THE BEAUTIFUL Longnose Hawkfish ( Oxycirrhites typus ) lives only on gorgonians and black coral trees in deep water. It specialises in stalking the small crustaceans that also live on its home. A SURGE-DWELLING hawkfish from the Galapagos Islands grows over 50 cm in length, but the largest Australian species is the Ornate Hawkfish ( Paracirrhites hemistictus ), which grows to about 29 cm. HOBBYISTS KEEPING Longnose Hawkfishes in aquariums have frequently reported egg-laying behaviour in this species. In the wild they are pelagic spawners like all other hawkfishes. THE RED AND BLACK Flame Hawkfish ( Neocirrhites armatus , below ) is very fussy in its habitat choice, living deep among the branches of only one or two species of live corals in exposed front reef habitats.
Class: Osteichthyes ( bony fishes ) Order: Pleuronectiformes Families: Soleidae & Plueronectidae
Conservation Watch 147 species in Australia; around 400 species worldwide. HABITAT: Sand and mud bottoms.
Triggerfishes are a distinctive group of tropical fishes that are named for the strong, lockable spine on top of the head. This is actually a highly modified first dorsal fin spine and it can be locked upright by the small second spine. This spine makes triggerfishes an unappetising prospect for potential predators.
RIGHT SIDE OR LEFT SIDE? Different flatfish families usually have the eyes consistently on either the right or the left side of the head. Soles are normally right-eyed.
SOME SPECIES OF SOLE and flounder are fished commercially in Australia, and they are generally regarded as a fine table fish. MANY FLATFISHES are very similar and are difficult to identify from photographs.
Text: Tony Ayling. Uncredited photography: Steve Parish
Conservation Watch 21 species in Australia; about 40 species worldwide. HABITAT: Coral reefs.
the FACTS!
RIGID BODY Above: Southern Peacock Sole
STRANGE TRANSFORMATION All flounders and soles have normal-shaped larvae that swim upright and have an eye on each side of the head. As the larvae get ready to metamorphose and begin bottom life, one eye migrates over the top of the head so that both eyes are on one side ( and twisting the skull in the process ). The newly settled young flatfish then lies on its side on the bottom so that both eyes are on the upper surface. The upper side retains normal colouration and the lower side becomes white. The mouth flattens and becomes distorted, and the body becomes “wider” and flatter. Soles and flounders have an amazing ability to change colour to match their surroundings.
UNDULATIONS Soles swim by passing waves down the fins and body and appear to undulate their way across the bottom. When disturbed, they will swim rapidly for a short distance then abruptly stop and apparently disappear as they blend in with their surroundings. This camouflage is so effective that these fishes can be hard to see even when you know where they are. Soles have separate sexes and probably migrate to offshore breeding grounds in the winter where they gather in groups to spawn. TONY AYLING
THE COCKATOO FLOUNDER ( Samaris cristatus ) has about a dozen very elongated, stark-white fin rays on its head that are normally kept inconspicuously folded. When danger threatens, these rays are flicked out ( like a cockatoo’s crest ) to frighten off potential predators.
Above: Clown Triggerfish
Above, left to right: Redtooth Triggerfish; Hawaiian Triggerfish; Orangestripe Triggerfish.
THE SOLE GENUS Pardachirus has toxin glands along the dorsal and anal fin bases and produces a milky poison that can stun would-be predators.
YOUNG OF THE SMALL Thickray Sole ( Aesopia cornuta ) have brightly coloured fins and appear to mimic toxic flatworms to discourage predators.
Class: Osteichthyes ( bony fishes ) Order: Tetraodontiformes Family: Balistidae
The family Soleidae is one of a group of nine similar families of flattened fishes commonly known as flounders and soles, which includes about 147 species in Australia. All these fishes are laterally flattened and swim on their side on the bottom, which requires one eye to migrate to the upper surface of the fish.
the FACTS!
SOME SPECIES OF FLOUNDER prefer neither the right side nor the left side, and the eyes may be on either side of the head.
— locking head spines
RON & VALERIE TAYLOR
Above: Mottled patterns help soles and flounders blend in perfectly with their surroundings on the bottom.
Osteichthyes
— flat fishes, weird eyes
Triggerfishes
Triggerfishes have a firm, diamond-shaped body and a flag-like, triangular tail. On the lower body the pelvic bone can be swivelled down, pulling out a flap of skin immediately below the dorsal trigger. Mirror-image soft dorsal and anal fins are present on the hind part of the body. These fishes do not swim using their tail fin but hold their body rigid and move by passing undulations down their dorsal and anal fins. This method of locomotion is remarkably effective, and a triggerfish in a hurry can swim very rapidly indeed! Triggerfishes have small mouths with powerful, lever-action jaws and close-set, chisel-like cutting teeth. This arrangement is suited to several feeding techniques. Some species are invertebrate-grazers, nipping encrusting growths from the bottom or crushing hard-shelled species, while others feed on large planktonic animals such as sea jellies. The huge Titan Triggerfish ( Balistoides viridescens ) uses its powerful jaws to break up pieces of living coral, digging down into branching colonies to get at invertebrates and small fishes hiding within.
WHEN LARGE TRIGGERFISHES are nest-guarding they may deliver painful attacks on divers that stray into their territory. Bites may draw blood but are not usually serious. HOW BIG ARE TRIGGERFISHES? Most triggerfishes are 20–75 cm long when fully grown. Males are usually slightly larger than females. TONY AYLING
Osteichthyes
Soles & flounders
Above: Triggerfishes guard their nest areas fiercely and have been known to attack divers.
FIERCE NEST-GUARDERS Most female triggerfishes guard territories within a much larger male territory. During the summer breeding season, each female prepares a nesting chamber on a sandy patch in her territory. She lays tens to hundreds of thousands of eggs within the chamber, which the harem male fertilises. Females constantly fan eggs to keep them oxygenated and fiercely defend their nests.
MANY HAREMIC FISHES are sex-changers but triggerfishes are born as male or female and do not change sex. WHEN THEY FEEL THREATENED, triggerfishes slide into carefully selected hiding holes in their territory and erect their triggers. This jams them firmly in their hiding hole. SOME TRIGGERFISHES, such as the Redtooth Triggerfish ( Odonus niger ), have adopted a pelagic lifestyle and live in schools well above the bottom, feeding on plankton.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au
Glossary
Glossary
— a key to survival
BARBELS Slender, fleshy feelers near the mouths of some fishes.
MOLLUSC An invertebrate animal with a soft body and, usually, a hard shell.
SEDENTARY Refers to animals that seldom move.
A rapidly increasing world population and increasing affluence has led to a greatly increased demand for seafood — two factors that are not good for fish populations. The ever-increasing worldwide fish catch has affected all fishes, but sharks and rays are particularly sensitive to strong fishing pressure. The demand for shark fins over recent decades has led to huge increases in the world’s shark catch, and many species are now chronically overfished. It has been estimated that fisheries kill more than 100 million sharks every year. Sadly, many of these sharks are killed as by-catch in the offshore tuna long-line fishery! Sharks and rays are not big breeders, giving birth to only a small number of large young every 2–3 years. To spread back into heavily fished areas, young sharks must swim under their own power and overfishing can easily cause local extinction. Most targeted shark fisheries have collapsed within only a decade of starting up.
BENTHIC Living on the bottom.
NOCTURNAL Active at night.
CAMOUFLAGE Protective colouration that blends with background.
MEMBRANE Thin connective tissue.
SEDIMENT Matter that settles on the bottom of a liquid, e.g. the silt and organic matter on the sea floor.
Bony fishes are not as susceptible to overfishing as sharks because they spawn hundreds of thousands or even millions of eggs each year, and have a planktonic larval stage; however, the history of fisheries around the world is littered with examples of overfishing and the collapse of key fisheries. The Atlantic Cod on the Grand Banks off Newfoundland ( USA ) has been reduced to about one hundredth of the original population by drastic overfishing. Fish species like the Orange Roughy, which do not mature until they are 30 years old and live for over 100 years, are particularly prone to overfishing. Many seahorses and pipefishes only produce a few hundred young each year, and these fishes also have a low sustainable catch level.
DORSAL ( FINS ) On the back.
No marine fish species has yet been driven to extinction by human fishing efforts, but three species of Australian fishes are listed by the government as “vulnerable to extinction” and another thirteen are said to be “nearly vulnerable to extinction”, including Barramundi Cod, Queensland Groper, Humphead Maori Wrasse, the Leafy Seadragon and Eastern Blue Grouper. We are fortunate in Australia — we have well-managed fisheries. However, many heavily fished species have suffered “size overfishing” with a high proportion of the larger individuals having been killed ( leaving only small fishes in the population ). Chronic overfishing is now common in marine fisheries and many have collapsed over the past 100 years. Recent studies have suggested that in all major fisheries for predatory fishes, fishers have now caught 90 out of every 100 fish that were present before fishing began!
EXTINCT When all individuals of a species cease to exist.
INCREASING FISHING PRESSURE
CONTINENTAL SHELF That part of a continent that lies under shallow seas. CLASPERS Male organs used to transmit sperm during mating. COMMENSALISM A relationship between two species whereby one benefits without harming the other. DIURNAL An animal that is active during the day.
ELECTRORECEPTION The ability to receive and make use of electrical impulses. ELONGATE Drawn out or long. EMBRYO Animal in developmental stage between conception and birth. ENDEMIC Occurring in one place/ location only.
GENUS The classification of a group of organisms that share many characteristics; a genus may contain one or more species. HABITAT Place where a particular animal or plant lives or grows. Area where a species is able to survive. TONY AYLING
Conservation
Conservation
HAREM A group of females that breed with and are protected by a single male. HERBIVORE Animal that eats plants. INCUBATE To keep eggs warm so they develop and hatch.
Right, top to bottom: Leafy Seadragon; Humphead Maori Wrasse; Barramundi Cod. Compared with many other countries in the world, Australia has managed its fisheries well. Protecting species from overfishing is vital to the health of the world’s oceans.
Text: Tony Ayling. Uncredited photography: Steve Parish
INVERTEBRATE An animal without a backbone. LARVA ( LARVAE ) Young form of an animal before it becomes an adult.
MIMIC To copy the looks and behaviour of another animal. MUCUS A slimy substance produced by some animals. OMNIVORE An animal that eats both plants and animals. OVIPAROUS Egg-producing animals ( whereby young hatch outside mother’s body ). OVOVIVIPAROUS Egg-producing animals ( whereby young hatch inside mother’s body ). PECTORAL ( FINS ) On the sides. PELAGIC Belonging to the open oceans. Oceanic. PELVIC ( FINS ) On the belly. PLACENTA Vascular sac connecting the circulatory system of an unborn animal to that of its mother. PLANKTON Plants and animals that drift in ocean currents ( usually microscopic ). PLANKTIVORE An animal that eats plankton. PREDATOR An animal that hunts and eats animals. PREHENSILE Able to grip. PROTANDRIC HERMAPHRODITES Animals that mature firstly as males, but then later change sex to become females.
SPAWN To release eggs or sperm into the water. SPECIES A group of organisms that can breed to produce fertile offspring with similar characteristics. SYMBIOSIS A close relationship between two different species. TAXONOMY The science of classifying ( describing and naming ) plants and animals. TEMPERATE Of medium temperature. TERRESTRIAL Living on land. TERRITORY Area occupied and defended by an individual or group. TOXIC Poisonous. UNDULATION A wave-like movement using alternate sides of the body. UTERINE CANNIBALISM Unborn young that feed on other eggs/embryos inside the womb. UTERUS A muscular pelvic organ where the young develop inside some female animals. Also called a womb. VERTEBRATES Animals with backbones. Includes fish, amphibians, reptiles, birds, mammals. VIVIPAROUS Gives birth to live young. XANTHIC A yellow colour form.
PROTOGYNOUS HERMAPHRODITES Animals that mature firstly as females, but then later change sex to become males. SCAVENGER An animal that eats dead animals.
From Steve Parish Publishing’s Amazing Facts: Marine Fishes ~ www.steveparish.com.au