'" CARD 11 ELECTRIC EEL "~ ___________________________________ G~R~O~U~P~4:~F~IS~H~~ ... ORDER ~ Cypriniformes

.,. FAMILY ~ Gymnotidae

.,. GENUS & SPECIES ~ Electrophorus electricus

The sinister-looking electric eel inhabits the dark depths of rivers and creeks. It is capable of producing a sao-volt shock that is

powerful enough to stun a horse.

KEY FACTS

SIZES Length: Up to 8 ft. Weight: 100 lb .

BREEDING

The electric eel's breeding habits are not known. The young are thought to hatch from eggs but even this is uncertain.

LIFESTYLE Habit: Solitary. Diet: Mainly small fish, also frogs. Young eels also eat invertebrates. Lifespan: The lifespan of the electric eel is not known. Range of the electric eel.

DISTRIBUTION RELATED SPECIES Although it looks like an eel, the electric eel is not a true eel, but a specially adapted fish related to carp and catfish .

Native to South America-found throughout the rivers of the Guyanas, the Orinoco river system, and the waters of the middle and lower Amazon basin.

CONSERVATION

Although it is eaten in South America, the electric eel has little value as a commercial food fish . Increased river pollu­tion presents the major threat to its survival.

THE EEL'S ELECTRICITY

The electric eel's electriCity-generating organs are in its long tail. They are made up of columns of wafer-thin electroplates-10,000 in all-and each produce a small charge. When activated, they produce brief bursts or pulses. At low voltage, the waves of electricity act like a form of radar. If the electric eel senses a fish passing by, however, it will increase the voltage to stun its prey.

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Electroplates (top) . Branches of nerve fibers (above) act as "chargers" within each plate.

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Frequently exceeding six feet in length,

the olive-brown electric eel has a long,

thick body and a broad, blunt head. The fish's

electricity-generating organs are situated in its

long tail, which accounts for more than

three-quarters of its total body length.

HABITS

The electric eel is an unusual fish because it is extremely inactive. It spends most of its time motionless.

The water it lives in is often poor in oxygen, so the eel comes to the surface occasion­ally for air. It swims by slowly moving its long and powerful

anal fin, which runs the length

of its body. Visibility in the murky water

is minimal, so the eel uses its electricity-generating organs to navigate in its surroundings.

Below: An electric eel at the water's surface gulps in air to obtain oxygen.

FOOD & FEEDING Young electric eels eat bottom­dwell ing invertebrates, but as eels grow, fish become their main source of food. The size of the prey depends on the eel's size.

The eel detects moving prey with its electric sensors. Even if the prey is still, the eel can de-

tect its presence. Its sensors are able to detect the weak electric impulses sent through

the muscles of fish as they breathe. When the electric eel senses that prey is nearby, it produces a series of high­voltage waves which stun or kill any fish within range.

~ BREEDING Almost nothing is known about the breeding habits of the electric eel. It is possible that it uses its electricity-generating organs to provide and receive information about the sex,

age, and mating receptiveness of other eels.

The electric eel disappears

Left: Almost blind, the electric eel catches prey using electric pulses.

Right: Male and female electric eels look identical.

DID YOU KNOW?

• The electric eel is the most lethal of all electric fish and is capable of producing a charge of 500-600 volts. Its head is positively charged and its tail

is negatively charged.

• Torpedo rays and electric catfish also produce electric

from its habitat at certain

times of the year and later returns with young electric eels no more than 4 inches

long. The young, called fry, are believed to hatch from eggs, but it is not known for certain. Where the electric eel breeds is another mystery.

charges. • Electric eels have been used for medical experi­ments, in particular in the treatment of rheumatism.

• Its electricity-generating organs account for at least half of the eel's weight.

"'" CARD 12 GREAT WHITE SHARK ~~--------------------------------------~ ... ORDER ~ Selachii

... FAMILY ~ Isuridae

... GENUS & SPECIES ~ Carcharodon carcharias

The great white shark is found in the warmer oceans throughout the world. It eats most types of fish and warm-blooded animals and

is the most deadly of the man-eating sharks.

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KEY FACTS

SIZES Length: Averages 10-20 ft. Weight: Averages 2,500 lb.

BREEDING Little is known of the great white shark's breeding habits. The female is thought to give birth to a single live pup; still, no pregnant white shark has ever been captured.

LIFESTYLE Habit: Solitary. Must move continuously. Diet: Almost any fish or warm­blooded creature it can catch. Lifespan: Believed to be 30-40

years.

RELATED SPECIES The whale shark (Rhincodontypus), over 60 ft. long, is considered the largest fish. The second largest, also a shark, is the basking shark

(Cetorhinus maximus).

• Range of the great white shark.

DISTRIBUTION In oceans worldwide, but mainly warm or temperate seas. Still, specimens have been found in the cooler waters off Nova Scotia, Iceland, and southern Australia.

CONSERVATION Because the great white shark is always on the move, it is impossible to monitor its numbers, and no population figures are available. It is thought to be rare.

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The great white shark is a solitary

animal and joins with other sharks only

to feed on a large kill. It must swim

continuously throughout its life to allow

enough oxygen to enter

its bloodstream.

~ FOOD &: HUNTING The great white shark preys on most ocean-going animals . It regularly eats such fish as tuna, marlin, and broadbill sword­fish, as well as sea lions, seals, and dolphins.

After eating large prey, the shark can survive for a month without eating again. The great white may feed when­ever prey is available, not just when the shark is hungry. Still, as its metabolic (body process) rate increases, especially in warmer waters, it eats more.

Most great white sharks hunt alone. But groups of sharks, attracted by blood

released from a kill, often gather to feed on dead prey.

The great white shark lo­cates its prey with its sharp sense of smell. Within its rostrum, or snout, are thou­sands of tiny holes that make up the shark's main nerve center. Thus, the great white is able to detect even the smallest amounts of blood in the water.

The great white also finds prey by echolocation, releas­ing sound waves that bounce back to the shark and enable it to determine an animal's exact location. Above: The shark's sensitive snout

is its nerve center. Right: The great white shark's body is massive and very strong.

~ GREAT WHITE SHARK &: MAN The great white shark has been responsible for many of the shark attacks on people. Its role in these attacks has been con­firmed by positive identifica­tion of great white shark tooth fragments recovered from damaged surfboards and boats.

The great white shark is con­§ sidered a prize catch by sport :§ fishermen. The shark is easily ~ recognized by its high, triangu­~ lar dorsal fin and crescent-a >. ro I-

~ left: A great white shark takes a lure from a boat. '

shaped tail. Although the great white

shark is killed for sport, it is not hunted for its meat. Be­cause the shark expels urine through its tissues and out of its body through its skin, its meat cannot be eaten.

Remarkably little is known about the great white shark. Attempts to study it in its natural habitat have failed because it is constantly on the move. It has also been impossible to keep the shark in captivity, so little study has been done.

r ~~ SPECIAL ~ ADAPTATION The great white shark has tri­angular teeth that grow as long as t hree inches. Serrated edges enable the shark to g rip its prey firmly . Like all sharks, the great white replaces lost teeth : a previously unused tooth emerges to replace the missing tooth .

Scientists believe that when a great white shark exceeds a certain length-to-weight ratio, it abruptly retreats to the ocean depths, where it remains for the rest of its life.

It is also believed that great white sharks, like blue marlin and wrasse, change sex when they reach a

DID YOU KNOW? • The great white shark is able to detect a single drop of blood in more than a million gallons of water.

• The great white shark must swim at a minimum speed of

certain size: the males be­come females . The reason for the sex change is not known, but it may ensure that all larger sharks give birth. This would increase their chances of producing healthy off­spring. The majority of the larger sharks caught have been female.

two miles an hour, 24 hours a day, to get enough oxygen into its bloodstream.

• If a great white shark is dragged backward, it drowns in minutes .

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"'CARD 13 CLOWNFISH \(~ ___________________________________ G_R_O_U_P_4_:_F_IS_H __ ~

~ ORDER Perciformes

FAMILY Pomacentridae

GENUS Amphiprion

The brilliantly colored clownfish gets its name from its distinctive black and white markings.

KEY FACTS SIZES

Length: 2-5 in., according to

species.

BREEDING Spawning season: Year round in

tropical waters.

Eggs: Laid in large batches.

Hatching time: 4-5 da,{s.

LIFESTYLE

Habit: Usually live in pairs within an anemone.

Diet: Leftovers from fish consumed by anemone; algae.

Lifespan: 3-5 years in captivity.

RELATED SPECIES Clownfish belong to the same

family of damselfish. They include

the common A. percu/a, the two­

banded A. akindynos, the black A.

me/anopus, the black-banded A.

ephippus, the white-maned A.

perideroin, and the Red Sea variety

A. bicinctus.

Range of the clownfish.

DISTRIBUTION Species are found in the Red Sea, the Indian Ocean and the

tropical Pacific Ocean. A. percu/a is particularly comm?n on

Australia's Great Barrier Reef.

CONSERVATION Having come under threat from the aquarium trade, many

governments are restricting the removal of the fish from their

natural environments.

CLOWNFISH AND THE SEA ANEMONE

The clownfish and the sea anemone have a symbiotic (or mutually beneficial) relationship. The clownfish attracts predators to the anemone in which it lives. The predator fish in turn become the prey of the anemone.

The clownfish also chases away certain fish that are harmful to the anemone. such as the butterfly fish . This fish preys on the anemone. biting off the ends of its tentacles.

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brightly colored fish called damselfish.

These inshore reef dwellers have

developed a curious and potentially

deadly relationship with

the sea anemone.

DID YOU KNOW? • The most common anem­one to act as host to the

clownfish is the large stoichac­tis species.

• If the slimy mucus covering

is wiped off a clownfish before it returns to its host anemone, it will be stung or even killed by the anemone's tentacles.

~ SPECIALADAPTATIONS It was once believed that the

clownfish had a natural immu­nity to the anemone's sting. However, studies have shown that this immunity must be

developed. The initial sting of an anem­

one causes the clownfish to secrete a slimy mucus which

covers its body and protects it

from further contact with the poisonous discharge of the

anemone's tentacles. This protective covering

protects the clownfish from its host anemone species, but it

can still be stung and killed by any other species of anemone against which it has not devel­

oped an immunity.

~ FOOD &: FEEDING The clownfish has a symbiotic, or mutually beneficial, relationship with the sea anemone. It catches most of its food by cooperating with its host anemone. The clownfish will leave the safety of the anemone's tentacles

and swim out among the nearby reef. Its brilliant colors attract larger fish, who, lured by the thought of a meal, follow it back to the anemone and are stung by the anem­

one's tentacles. The anemone then consumes the fish, and the clownfish feeds on the remains.

In addition to other fish, the

clownfish also feeds on planktonic crustaceans and

algae that live in or grow on the reef. The clownfish also eats away debris and nibbles off the dead tentacles of its host anemone.

Right: The blackish yellow two­banded variety, A. akindynos, swims among the sea anemones, feeding on planktonic crustaceans and algae.

~ BREEDING Clownfish lay their eggs in

batches on the clear coral or

rock adjacent to the anem­

one, or at the base of the

anemone's tentacles. The

male guards the eggs until

they hatch 4-5 days later. In

some species of clownfish,

the male cares for the young

until they reach sexual ma­

turity, at which time they

leave to find their own host

anemone.

Left: The Red Sea species, A. bicinctus, is bright yellow­orange with two white bars-one behind the eye, the other across the middle.

Right: Most clownfish spawn on coral near their host anemone or within the anemone itself.

reefs for thousands of years.

But more recently, they have become extremely popular as saltwater aquarium fish. The

brightly colored species command a high price in

Europe and the United States. Collectors, realizing the

demand, have destroyed many reefs in search of prime speci­mens, often damaging or killing the host anemones in

the process.

. Fortunately, many local governments have imposed restrictions on the number of

clownfish that can be taken from their habitats and the

means by which they can be taken. And, because clownfish are a big attraction with snorkelers and scuba divers, the tourist industry has an interest in protecting them and

ensuring that they be allowed to live and breed safely on the reef.

ANGELFISH

ORDER Perciformes

FAMILY Pomacanthidae

GROUP 4 : FISH GENUS & SPECIES Pomacanthus

Angelfish are among the most colorful of marine animals. Coral reefs, found in tropical seas around the world,

are their natural habitat.

KEY FACTS

SIZES Length: Up to 2 ft. but usually

much smaller.

BREEDING Little is known about the breeding

habits of angelfish in the wild, and

they do not breed well in captivity.

Probably spawn as pairs, produc­

ing hundreds of eggs.

LIFESTYLE Habit: Active by day, either

solitary, in pairs, or in small groups.

Diet: Algae, worms, shellfish, and

sponges.

Lifespan: Unknown in wild .

RELATED SPECIES There are 74 angelfish species.

Their closest relatives are the

similar butterflyfish (family

Chaetodontidae), including the

forceps fish Forcipiger /ongirostris.

Range of the angelfish.

DISTRIBUTION

Angelfish are found throughout the world in tropical and

subtropical shallow seas, usually on coral reefs.

CONSERVATION

Despite collection for aquaria, angelfish are in no direct

danger from man . However, in areas such as the Caribbean,

pollution and coastal development pose a considerable

threat to their coral reef habitat.

COLORFUL ANGELFISH VARIETIES

Pterophyllum: Freshwater ornamental species bred for its long fins.

Blue-lipped: Flat­bodied with black fin; eats plant material.

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Blue : Body, fins , and gills edged with blue; plant­eating.

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Angelfish are a favorite subject of underwater

photographers, but little is actually known about their

behavior. In many ways they are unique,

changing their color, pattert'~and even their sex-

as they mature.

~ HABITAT The angelfish is so brilliantly colored it seems unlikely that it could escape the attention of predators. Some people have assumed that the colorful angelfish in home aquariums are a special breed-that angelfish in the wild are drab and dull­colored. But in fact all angelfish have bright colors and distinct markings.

Angelfish are found on coral reefs in tropical and subtropical seas throughout the world. Of the seventy­four different species of angelfish, the blue-lipped, emperor, and blue angelfish are among the most colorful (see back cover).

Above: Angelfish Holacanthus berrnudensis ona Florida reef.

DID YOU KNOW?

• The markings on some young angelfish look like

Arabic script. In Zanzibar, an angelfish was spotted that supposedly had "There is no God but Allah" written on one side, and "A warning sent from Allah" on the other.

• Some angelfish have markings near their fins that resemble eyes, called eyespots, that confuse predators and keep them away from the fish's head .

• In some species of angel­fish, such as the emperor angelfish, the young fish have different markings than the adults .

Right: A blue-girdled angelfish Euxiphipops navarchus.

~ BREEDING One of the most unusual things about reef-dwelling fish is the way many species, including certain angelfish, change sex as they grow. Most often it is the mature females who change into fully function­ing males. In some species, the change in sex is automatic; in others, the change is circum-

~ BEHAVIOR On the rich feeding grounds of the reef, most angelfish can find enough food within a relatively small area. Singly or in groups, fish will often jealously defend their feeding grounds against others of the same species. They flaunt themselves so that the intrud­ers recognize their distinctive markings and retreat without a confrontation.

Some angelfish, such as the blue-and-gold dwarf angel­

fish, Centropyge bic%r, claim territory within a small, algae­rich area of the reef. They live in family groups dominated by a single male. Other family groups are kept out of the territory-partly by the ag­gressive behavior of the male

stantial. A static group consists of a

single male and his harem of females. The largest and old­est female, however, changes sex and takes over his position once he dies, defending the group and fertilizing the eggs.

Little is known about the spawning behavior of angel-

and partly because of the warning indicated by the group's bright coloration.

It has been suggested that the bright markings of many angelfish act as camouflage, enabling them to blend in with their surroundings. But according to most scuba divers, an angelfish is visible for many yards through the clear water.

Since its bright coloration does not protect it from predators in all cases, the angelfish is also able to slip into tight crevices out of reach of its predators. Its deep, flattened body has de­veloped partly as an adapta­tion allowing it to squeeze into narrow spaces.

fish. The spawning (producing or depositing eggs) of most reef fishes takes place above the reef. The male and female dash toward the ocean surface, shed the eggs and sperm, then dive back to the shelter of the coral. The fertilized eggs float off in the currents, away from reef

~ FOOD &: FEEDING Many species, such as the dwarf angelfish, are primarily plant eaters. They scrape algae off rocks with fine, brushlike teeth. This activity also helps keep the algae in check.

Larger species such as the emperor angelfish Pomacan­

thus imperator, eat shrimp, worms, and shellfish. They have strong, beaklike jaws with which to crush prey. Some an-

predators. The larvae that hatch from the

eggs may drift off into the open sea, either to die or to settle on another reef. Only a small proportion survive to maturity.

Below: The blue angelfish Porn acanthus sernicirculatus.

gelfish species have protrud­ing mouths which allow them to probe for food in crevices between the corals.

Occasionally, an angelfish will eat parts of a coral polyp -one of the tiny, anemone­like colonial animals that are part of the reef-and seems to be unaffected by the stinging cells in the polyp's

tentacles.

CICHLID

ORDER Perciformes

FAMILY Cichlidae

GENUS Various

Popular as tropical aquarium fish, cichlids are famous for their courtship displays and their devotion to their young. But in

the wild, the cichlids have some even more unusual habits.

KEY FACTS

SIZES Length: 4-12 in ., but some predatory species up to 21/2 ft.

BREEDING Spawning season: Varies according to species and location . No. of eggs: Up to several hundred. Hatching period: 3-5 days.

LIFESTYLE Habit: Form schools until the males adopt breeding territories. The territories are later aban­doned and the schools reform. Diet: Varies according to species.

RELATED SPECIES Cichlids are members of the vast Perciformes order of perch like fish, relatives of the mud-skippers and the fighting fish.

Range of the cichlid .

DISTRIBUTION Except for two species found on the coasts of south India and Sri Lanka, cichlids are freshwater inhabitants of lakes and rivers in Africa and tropical Central and South America .

CONSERVATION Pollution, water management schemes, and the introduct ion of new species threaten their often specialized habitats. Collection for aquariums does little harm to their numbers.

SOME DIFFERENT SPECIES OF CICHLID

Te/amaloehromis rittalus: A "crevice dweller," its narrow body is adapted to search ing for food in the crevices between rocks.

Lapidoehromis vellieans: A carnivorous bottom­dweller, its narrow, sharp teeth pull shrimp and aquatic insects out of the crevices in the seabed. Large eyes help identify prey.

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Hap/oehromis maerosloma: One of many species of predator that use vicious tactics such as biting scales, or even chunks, off other fish .

An/onoeara nyssae: A mouth-brooder-once the eggs are laid and the male has released sperm into a pit, the female gathers the eggs and sperm into her mouth for fertilization.

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Cichlid species are constantly

evolving. Over millions of years, the

cichlids of East Africa have evolved into a

huge range of more than 600 different species

with every conceivable lifestyle. Yet they all share

a loyalty to their partners and young-

this is characteristic of their family.

~ HABITAT Nearly all the 1,000 species of cichlid fish live in lakes and rivers in Central and South America and Africa, and more than half occur in East Africa's great lakes.

There have been many climatic changes affecting these lakes over millions of years. The water levels have decreased several times, exposing ridges on lake beds and forming many smaller lakes. It is likely that many

species of cichlid evolved to survive the special conditions of the isolated pools.

The cichlid has little com­petition from other fish in these lakes, so it has diver­sified into a variety of closely related but distinct species to fill every niche in the eco­system. Nearly 300 species of the family Haplochromis live in Lake Victoria-and each species has its own feeding and breeding habits.

~ SPAWNING Territorial when breeding, the male claims a small section of the lake bed. Boundary dis­putes between territorial neighboring males are settled by threats. Glowing with heightened color, the male will patrol the area with fins bristling, ready to attack any intruder. Soon the males respect each other's bound­aries and neither one will pass through the other's.

For a nest, the male cichlid cleans large stones to receive eggs or digs a breeding pit in

Left: The bright colors of many cichlid species make them popular aquarium fish.

DID YOU KNOW? • Mating cichlids often stay together longer than neces­sary to raise young-this is a unique bond among fish .

• Some cichlids have devel­oped into predators of their mouth-brooding relatives, harassing the parent fish until it coughs up its brood

the gravel, pushing the soil to the boundary to make a shallow protective wall. Then he attracts a mate with a graceful and vibrant color display.

The parents take turns guarding the fertilized eggs, fanning them constantly with their fins to keep water flowing through the clutch . This oxygenates the eggs and helps prevent infection. When the fry are newly hatched, the parents guard them closely. At first the fry lie in the nest cavity, but they soon move around as the parents watch carefully. At night a parent

of eggs or fry. • The cichlid Haplochromis livingstonii preys on scaveng­ing fish by pretending to be dead. The scavenger is lured by the prospect of a meal, and when it comes close enough, the cichlid eats the would-be predator.

often gathers them up in its mouth to protect them.

Some female cichlids use their mouths as nests, gath­ering and holding the eggs and sperm there to fuse and develop into fry.

~ FOOD &: FEEDING Isolated in lakes, various cich­lids have evolved in different ways to survive on a variety of food sources.

The more placid cichlids only eat vegetation. Some have rows of small rasping teeth for scraping algae off rocks; others have bladelike teeth for shearing through the stems of water plants. Some

Left: Male cichlids use their strong jaws and lips to defend their territory.

Above: The Below: fry of species Cichlids use that are not breeding pits mouth- or slabs of brooders feed specially on their par- cleaned stones ents'mucus to receive the secretions. eggs.

cichlid species filter micro­scopic plants from the water by using their gills as strainers.

Carnivorous species use their protruding, needlelike teeth as tweezers to pluck shrimp and aquatic insects out of crevices. In contrast, another species has flattened teeth that crush the shells of mussels and snails. Predatory cichlids have large mouths and strong, pointed teeth to catch and eat other fish.

CARD 16 WELS CATFISH

ORDER Siluriformes

.... FAMILY ~ Siluridae

GENUS fir SPECIES Silurus glanis

The freshwater Wels catfish nightly patrols the weed beds and the rim of its murky lake or river home.

It is a danger to all unsuspecting smaller fish.

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KEY FACTS

SIZES

Length: Averages 5 ft., but can

grow to 16 ft. • Weight: About 200 lb.; largest

over 700 lb.

BREEDING

Sexual maturity: 4-5 years.

Spawning season: May to July.

No. of eggs laid: 100,000-370,000.

LIFESTYLE

Habit: Solitary; nocturnal.

Diet: Fish, small mammals,

reptiles, and birds.

Lifespan: Up to 15 years .

RELATED SPECIES

The only other species found in

Europe, Silurus aristotelis, is found

in southern Greece. It can reach a

length of 6 ft . and weigh as much

as 350 lb.

Range of the Wels catfish.

DISTRIBUTION

Once con fined mainly to eastern Europe, the Wels catfish's

range now extends into western Europe and England. It is

also found in brackish waters of the Baltic and Caspian seas.

CONSERVATION

The Wels catfish is not an endangered species.

FEATURES OF THE WELS CATFISH Body: Broad at head; flattens toward back. Usually a brown-green color.

Tail lin

: Scaleless (the reason these catfish are sometimes called "naked" catfish).

Head: Flat with broad mouth; many tiny teeth form brushlike pads that grip and hold food in the fish's large jaws.

Dorsal fin

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The huge Wels catfish feeds

mainly on live fish. It also eats

small mammals, amphibians, and birds

that might be in the water. But catfish

sometimes scavenge for carrion,

so sport fishermen use animal meat as bait.

~ BREEDING The Wels catfish spawns from May to July, depositing its eggs under weed beds. First, the male digs a shallow hole

Right: Of the thousands of eggs laid, only a small number will survive to maturity.

with his nose, then the female lays her eggs in the hole. She can produce from 100,000 to 370,000 eggs,

~ FOOD & HUNTING On its nightly hunting trips the adult catfish stalks and catches live fish, including the young of other catfish. It uses its long­est pair of whiskerlike barbels (feelers) to forage along the muddy bottom for small inver­tebrates.

depending on her size. The male guards the eggs for

two to four days, until the young hatch. Then the black

Fish is the Wels catfish's basic diet, though it also eats water voles, ducklings, frogs, and crayfish. Sometimes it will surface to gulp down swimming amphibians, birds, and even small mammals in the water.

tadpole-shaped fry (young fish) fend for themselves. They feed mainly on tiny invertebrates.

Right: Close­up of catfish head showing the barbels, or feelers, on its top and bottom jaws.

Left: The Wels catfish, sometimes called the European catfish, is popular with fishermen.

~CATFISH & MAN In Eastern Europe catfish are an important commercial fish. They are caught in nets, in large traps, or even on baited lines.

In some areas the fish are successfully farmed because they are content to live in an artificial environment where food is readily available. Un­der these favorable condi­tions they grow rapidly and reach a marketable size quickly. Their meat is eaten fresh, salted, or smoked.

Catfish are also a popular sport fish in several European countries.

~ HABITS The Wels catfish feeds mainly at night. It rests during the day in the shelter of over­hanging or weedy banks, or on the muddy bottom of deeper water in slow rivers and muddy lakes.

It prefers to spend its time in an almost static position. It never jumps, although it sometimes rolls just under the surface.

A loner, the catfish establishes and defends its territory. However, food-rich waters can support several catfish in the same area.

DID YOU KNOW? • In Asia "walking" catfish have lunglike organs that let them breathe on land. They can pull themselves along on land with their fins .

• There are more than 2,000 species of catfish, from 30 families . They vary in size from smaller than a half inch to 16 feet.

• Only two families of marine catfish exist: Plotosidae and Aridae. The Aridae male carries the fertilized eggs in his mouth for as long as two months and does not eat during this time.

COMMON STURGEON

ORDER Acipenseriformes

.... FAMILY ~ Acipenseridae

""" CARD 17

GROUP 4: FISH GENUS & SPECIES Acipenser sturio

The common sturgeon has changed very little since the age of the dinosaurs. At that time its ancestors were

among the most abundant fish in the seas.

KEY FACTS

SIZES Length: Male, 3-5 ft. Female, 4-7 ft. Can reach over 11 ft.

Weight: Up to 600 lb.

BREEDING Sexual maturity: Male, 7-9 years.

Female, 8-14 years . Spawning season: May to June. Eggs: Up to 2.5 million. Hatching time: 3-7 days.

LIFESTYLE Habit: Migratory. Bottom living. Diet: Crustaceans, polychaete worms, mollusks, and small fish. lifespan: 100 years or more.

RELATED SPECIES Closest relative: Acipenser

oxyrhynchus, in the northwest Atlantic. Other relatives: A. fulves­

cens, lake sturgeon; Huso huso,

beluga; and H. dauricus, kaluga.

Range of the common sturgeon.

DISTRIBUTION

The adult common sturgeon is found in the Black Sea and its associated rivers, the northern Mediterranean, and the northeast Atlantic coast from Morocco to Norway.

CONSERVATION

Fishing, pollution, and obstructions across spawning rivers

have greatly reduced the sturgeon's population. It has become rare within all but the eastern portion of its range.

LlFECYClE AND FEATURES OF THE COMMON STURGEON

1 Roe (eggs): In early summer a female spawns more than two million roe, each less than a tenth of an inch long . They stick to the river bed and hatch in three to seven days.

Barbels: Sensitive feelers below the snout detect prey on the river or sea bed. The mouth then extends like a tube to scoop up prey.

2 'fhe newly hatched larva is about a third of an inch long . It feeds from an attached yolk sac.

3 Within six months to a year the fry (young fish) develops a primitive mouth and barbels (see below).

Scutes: Rows of bony plates, called scutes, lie along the sturgeon's back, flanks, and belly. The scutes may once have protected the sturgeon's ancestors from predators.

~

e

e

4 The sturgeon develops in fresh water for three years before swim­ming to the sea, where it stays until it becomes sexually mature.

The common sturgeon is one

of the largest fish to use rivers and

lakes for breeding grounds. Some

sturgeons grow to several yards in length

and may outlive humans. Widespread

commercial fishing has left few of

these older and larger specimens.

~ HABITS

The common sturgeon is a bottom-dwelling fish, spend­ing much of its time inshore, where the seabed is 50 to 150 feet deep. It is the only European sturgeon that can live in full salt water as well as in the brackish (mixed salt and fresh) water of estuaries. After spawning in fresh water, some

adult sturgeons remain near the mouths of their breeding rivers, while others travel more than 600 miles throughout the seas of their range.

Pollution and the dams and

weirs that obstruct spawning rivers have taken their toll on

the sturgeon population. While the common sturgeon remains fairly numerous in the Black Sea between Turkey and the Soviet Union, it is now a rare visitor to the northern European coast. Only a few are caught in British waters, for example. In southwestern Europe the sturgeon is concentrated in just a few places, such as around the French Gironde estuary and the mouth of the Guadalquivir River in Spain .

Right: Sturgeons now rarely reach the size of specimens found in the days before overfishing.

Left: The mouth of the common sturgeon can project outward to form a sucking tube that scoops up prey from the sea­or riverbed. The touch­sensitive barbels under its snout help it to detect the prey.

DID YOU KNOW? • In some areas, such as the Gironde estuary in France,

young sturgeons grow faster than average. There, the young fish reach about 15

linChes in their first year.

• Sturgeons were once so plentiful in North America that dishes of caviar were

~ BREEDING In March or April, adult com­mon sturgeons enter river mouths and begin swimming upstream. Some fish remain in the lower sections of the rivers, but others make their way 300 or more miles inland. In the past, when the rivers were more habitable, the common sturgeon spawned as far as 600 miles from the sea.

Spawning occurs in May and June. Each female produces a vast number of eggs-up to 2.5 million . The sticky roe

provided free in bars.

• In the Black and Caspian seas the beluga have been known to reach 16 feet in

length.

• More than 12,000 tons of sturgeon are caught every year in the Black and

Caspian seas.

(eggs) adhere to stones or plants on the river bed, and the adult returns to the sea .

The eggs hatch in three to seven days, depending on water temperature. The larvae, abou,t a third of an inch long at first, grow stead­ily-to about four inches in the first year. They continue to develop in fresh water for up to three years before

leaving for the sea, where they remain until mature enough to spawn.

~ FOOD &: FEEDING

The sturgeon forages for food on the seabed, using its long, shovel-shaped snout to root around in the mud and sand. Four sensitive barbels (feelers) under its snout feel for edible

morsels. For its size, the common

sturgeon feeds on fairly small

prey: mainly invertebrates

~ STURGEON &: MAN Commercial fishing increas­ingly threatens the common sturgeon. Fishermen hunt the sturgeon for both its flesh and its roe, which is proc­

essed to become caviar. After the roe is taken from

the body of a mature female, it is soaked in brine, then pressed, packed in contain­ers, and exported as a lUXUry food. Commercial fishing is

still a major industry in the Soviet Union and around the Black and Caspian seas.

such as mollusks, worms, and

shrimp. A larger adult will also eat small fish such as gobies and sand eels. During its spawning trips up rivers, the sturgeon does not eat at all.

The fry (young fish) devel­oping in the rivers feed on freshwater prey, such as insect

larvae and aquatic worms.

CARP

ORDER Cypriniformes

FAMILY Cyprinidae

CARD 18

K GROUP 4: FISH ~ .; .. ~

GENUS &: SPECIES Cyprinus carpio

The carp is a highly adaptable freshwater fish. It was once found only in Asia, but it is now common throughout much of the world.

KEY FACTS

SIZES Length: Average 30 in.

Weight: Average 20 lb., but in

rare instances females can reach

90 lb.

BREEDING

Sexual maturity: 2-3 years.

Spawning: April to July.

No. of eggs: Up to 2,000,000

from a 20-lb. fish . Hatching period: 6-10 days.

LIFESTYLE Habit: Extremely cautious; lives

in small schools. Diet: Worms, shrimps, water

snails, freshwater mussels, aquatic

insects, nymphs, some vegetable

matter. lifespan: 20-25 years in the wild.

RELATED SPECIES

There are about 2,500 species of

Cypriniformes. Goldfish and roach

are in the same order.

FEATURES OF THE CARP

Carp avoid clear, fast-flowing waters and shady or cold areas. Instead, they prefer shallow, sun­lit waters with plentiful mu and plant growth on the botto .

©MCMXCI IMP BV/I MP INC WILDLIFE FACT FILETM

• Range of the carp.

DISTRIBUTION

Originally native to Japan, China, and Central Asia, the carp

has been introduced into most of Europe and North America,

as well as in parts of Africa, Australia, and New Zealand.

CONSERVATION

Carp breed so successfully wherever they have been intro­

duced that they have reached plaguelike proportions in some

countries, destroying stocks of pike and trout.

PRINTFn IN II S A 01hO~00141 PAr.KFT 14

Most carp are plain colored

and have greenish brown sides and

blue backs. But the valued and

exotic koi carp that are bred in Japan are

brilliantly colored in contrast to their

common carp relatives.

~BREEDING Carp mate in shallow water from April to june. A single 20-pound female can lay up to 2,000,000 eggs. She us­ually places them on the leaves of aquatic plants.

The fry (young fish) hatch

~ FOOD &: FEEDING Carp use the four barbels

(threadlike growths that function as organs of touch) located around their mouths to find food in the soft mud of the riverbed. They eat worms, shrimp, water snails, freshwater mussels, aquatic insects, nymphs, and water lilies and other plant matter.

Occasionally carp rise to the water's surface to feed on aquatic insects. Carp make a characteristic slurping noise

Right: A bottom-feeding fish, the carp uses the four barbels, or touch organs, around its mouth to feel in the mud for worms and other prey.

within 6 tol 0 days, and they tend to remain in shallow water near the riverbank. At this stage the young are ex­tremely vulnerable to attack from most other fish, includ­ing their parents.

as they ingest air and water along with their prey.

Carp do not have true teeth. Instead, they use their throats like grinders to crush the shells of water snails and mussels. The carp then eject the shell fragments and swallow the flesh.

Right: Carp prefer the food-rich, muddy shallows of slow-moving waters and lay their eggs there in early summer after mating near the surface.

~HABITAT Carp live mainly in large riv­ers, although they can also be found in most fresh waterways. They prefer shallow, slow­moving water in areas that have an abundance of aquatic plant life.

Carp live in small groups

DID YOU KNOW?

• The age of a carp can be determined by counting the rings on its scales; each ring indicates a spawning year. • In the Soviet Union, carp have been selectively cross­bred to grow at a faster rate; they gain 9 pounds a year.

• japanese carp breeders claim that some koi, a type of carp, are 200 years old .

rather than in schools. They spend much of the time lurking in the weeds at the bottom of riverbeds. On hot afternoons they rise to the surface to bask in the sun. At night they emerge from the weeds to search for food.

• Carp were introduced into central Africa to provide food for European expatriates.

• In Eastern Europe, carp are often served as the traditional main course at Christmas dinner.

• At the palace of Versailles in France, carp have been taught to pull bell ropes to indicate that they are hungry.

~ CARP&:MAN Of all fish, the carp has had the longest association with man. It has long been used for food, as an ornament, and as sport for fishermen. Aris­totle made the earliest known reference to them in 550 B.C. Since that time carp have been introduced to countries throughout the world.

Carp have been selectively bred as ornamental fish for

Left: On a hot day, carp may be seen at the surface of the water, basking in the sunlight.

thousands of years. The japanese have bred the carp most successfully. They pro­duce a variety known as the koi carp. The koi are brilliantly colored fish and may be black and red, pure white, white with a red mark on the head, black and white, black and orange, or blue. They are con­sidered to be extremely valuable.

ANGLER

""'---------... ORDER ... FAMILY "1IIIIIIII Lophiiformes "1IIIIIIII Lophiidae

GROUP 4: FISH GENUS &: SPECIES Lophius piscatorius

The angler is one of the ugliest fish in the sea, and one of the most efficient predators, since it relies on

its victim's curiosity to lure it to its doom.

KEY FACTS --~-----~------- -~.---~--~~----------------------------------------------

SIZES Length: Up to 6 ft. Weight: Up to 90 lb.

BREEDING Spawning: Spring and early

summer. No. of eggs: Unknown, but probably over a million, enclosed

in a single egg mass.

LIFESTYLE Habit: Solitary, bottom-dwelling. Diet: Smaller fish that feed near

the seabed. Lifespan: Unknown.

RELATED SPECIES

There are 215 species of angler, found mostly in warm waters and including deep-sea anglers such as the Atlantic football fish, Himant%phus groen/andicus.

FEATURES OF THE ANGLER

Range of the angler.

DISTRIBUTION

Coastal waters off Europe and northwest Africa (including the Mediterranean) from six feet to a quarter mile below the low tide line.

CONSERVATION

Although occasionally caught and sold in fish markets, the angler is not regarded as an important commercial species, and is in no danger of extinction .

Fish lure: Tipped with a flap of skin and wiggled to make it look like a small fish. The lure has evolved from the dorsal

Camouflage: Irregular fleshy flaps break the outline of the angler and ?

help hide the fish when it is lying ,on the bottom. Its coloring also hetps it blend in with the seabed .

,Body: The rear part of the body is almost never used and thus has atrophied (shrunk in size). The huge head and mouth replace the need ' for the fish to move at great speed when catching its prey.

©MCMXCIIMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A. 0160200221 PACKET 22

The angler has perfected the art of ambush.

It lies motionless on the seabed, half-buried

in mud and sand, and lures passing fish

into its cavernous mouth with the aid of

a specially adapted fin on top of its head,

which it uses like a fishing rod.

~ HABITS Unlike other fish, the angler does not expend a lot of energy chasing its prey. Instead, this fish lurks in am­bush, without twitching a muscle, and gulps down its victims when they swim too close. Its success at catching prey depends upon its good camouflage as well as its perfect timing.

The angler's body is perfect-

Iy adapted to life on the seabed, where it spends nearly all its time waiting for prey. It is fringed and flat­tened, with small flaps of skin that look like strands of sea­weed. These mask its outline and make the angler almost invisible as it lies motionless and half-buried in the sand.

The angler spends much of its life immobile and requires

~ BREEDING In spring and early summer anglers stir from the seabed and swim into deep water. In the north Atlantic they move into waters over a mile deep, but instead of following the ocean floor they stay near the surface to spawn (breed).

The eggs are laid in great

little oxygen, so it has relatively small gills and gill openings. It also has little need for pow­erful swimming muscles; as a result, the hind part of the angler's body is shrunken­the fish is little more than a vast mouth with fins. The largest of the angler's fins are the fleshy pectorals, which the angler uses to propel itself across the ocean floor.

numbers, encased within a huge ribbonlike sheet of jelly, which may be as much as 30 feet in length and six feet in width . The sheet drifts on sur­face currents until the young are ready to hatch.

When the angler fish larvae first hatch, they swim near

Left: The angler consumes virtually anything that comes close.

Right: The angler's enor­mous mouth gives it maxi­mum suction when capturing its prey.

~ FOOD & FEEDING The angler owes its name to its technique of "fishing" for its prey. Just above its mouth is a lure, a long rod tipped with a fleshy flap of skin. It uses this lure as bait to attract its prey. As the angler moves the rod slowly through the water, the flap of skin on the end wriggles like a worm.

Mesmerized by the twitching

DID YOU KNOW? • Anglers are greedy fish, and those caught in trawl nets usually have full stom­achs because they have gorged themselves on other fish in the net before being hauled out of the water. • The flesh of the angler

the surface, feeding on tiny sea life; when they reach two to three inches long they drift down to the seabed to live.

Male and female anglers look alike, but in some deep­sea species, the male is tiny compared to the female .

lure, the fish swims closer, un­aware of the well-camouflaged angler. The angler manipulates the lure to maneuver its victim into position directly above its mouth. Then, with a snap, the fish is gone.

The angler's strike is faster than the eye can follow. It does not leap at its prey, but simply opens its cavernous

tastes like shrimp. Fish mar­kets often sell the tail of the angler, and cut off the head to avoid scaring customers. • Although anglers usually feed on the bottom, they oc­casionally surface, as evi­denced by an angler that

Anglers breed in a very unusual way. Instead of fertil ­izing the eggs after they are laid, the male attaches him­self to the female's body and becomes fused to her. He is nourished by her blood­stream while she uses his sperm to fertilize her eggs.

mouth so rapidly that a great volume of water floods in, taking the victim with it. Needle-sharp teeth inside the angler's mouth make escape impossible. As the water clears, the angler swallows its meal and settles down to wait for another unwary fish to swim close to its hiding place on the seabed.

was once found choked to death on a seagull. • Deep-sea anglers attract their prey in the same way as their shallow-water relatives, but because the ocean depths are dark, they have luminous lures.

NORTHERN PIKE

The pike's drab coloring and good vision are adaptations to life as an underwater predator. It is well camouflaged as it hides in the

weeds, and it can spot prey as for as SO feet away.

KEY FACTS

SIZES

Length: Females, up to 5 ft. Males are smaller. Weight: Males, rarely more than

11 lb. Females, up to 55 lb.

BREEDING

Spawning season: March and

April. No. of eggs: 40,000-500,000. Hatching time: 2-3 weeks.

LIFESTYLE

Habit: Predatory; ambushes prey rather than hunting actively. Diet: Mainly other small fish. Will also eat young coots and ducks. Lifespan: Average 7-10 years.

RELATED SPECIES

Relatives of the pike include the muskellunge, Esox masquinongy; grass pickerel, E. americanus; and chain pickerel, E. niger, from North Americai and black-spotted pike, E. reicherti, from the Soviet Union.

THE PIKE'S TEETH

The pike's long jaw houses a mouthful of sharp teeth , designed to grip the most slippery of fish.

the upper jaw, there are umerous small teeth-found

even on the roof of the mouth -which point backwards and make escape impossible. The strong teeth in the lower jaw grow straight.

©MCMXCI IMP BV/IMP INC WILDLIFE FACT FILETM

"Range of the northern pike.

DISTRIBUTION

Throughout Great Britain, except for Hebrides, Orkney, and Shetland, and throughout Europe except for Spain and

Portugal. Related species are found in the United States and parts of Asia and the Soviet Union.

CONSERVATION

Pike have few natural enemies, but numbers are kept balanced by sport fishing and their own cannibalism.

lower jaw teeth are longer and straighter than the

/ top teeth.

PRINTED IN U.S.A

Upper jaw teeth slope backwards so prey cannot escape.

0160200111 PACKET 11

Although it is one of Europe's most predatory fish,

the pike is not an active hunter. Instead it prefers to hide

in the weeds at the bottom of a lake or stream,

waiting for prey to swim by.

~ FOOD &: HUNTING The pike preys mainly on different types of carp, although it will eat most other fish as well, including roach, rudd, and bream. It also eats frogs, swimming voles, rats, and small water birds such as mallard duck­lings, moorhens, and coots.

A young pike differs from a mature pike in that it actively pursues its prey. It feeds on water fleas, worms, and young fish. As it gets older, it catches prey by remaining motionless, waiting for an unsuspecting victim to swim within range. Its dorsal and anal fins are

~ HABITAT Pike are found primarily in lakes, rivers, and reservoirs. They prefer deep, calm, or slow-moving water where the weeds are fairly dense. They

positioned far back on its body, which makes it capable of rapid acceleration.

Prey is detected by sight and a northern pike can spot a po­tential meal 50 feet away. It is thought that vibrations in the water may also help lead the pike to its prey.

usually hide in these weeds, away from the main current.

The fish's coloration varies according to the waters it inhabits. The most vividly

Far right: Fins placed far back on the body help the pike to mo\'e; quickly.

Below: Shoals of smaller fish are common victims of the pike.

DID YOU KNOW? • A pike can swallow large fish because its mouth is wide and because the prey passes directly into its long, straight intestine. Still, it takes three to five days for its di­gestion to be completed. • A pike's brain accounts for

colored specimens are found in clear water. Their mottled green scales allow them to blend in with weeds and reed stems.

Left: Pike wait on the river bottom to ambush prey.

Below: The pike's eyes are well placed for hunting.

less than one thousandth of its total body weight.

• Although the pike is a fairly indiscriminate feeder, it does not prey on sticklebacks be­cause of their sharp spines.

• The pike has highly acidic digest ive juices which can

~BREEDING Pike generally spawn in late March or early April in reed beds or in shallow streams. The number of eggs pro­duced depends on the size of the fish. The larger the fish, the more eggs it produces.

The eggs remain on or just aboye the bottom of the lake or stream until they hatch two to three weeks later. Larvae feed off the yolk sac for 10 days, until it is completely ab­sorbed. The young pike are then ready to hunt for prey.

The pike's voracious appetite ~ has long put it at odds with ~ man. Fish farmers net it be-~ cause it eats trout and salmon;

~ gamekeepers kill it because it ~ eats ducklings. Anglers regard ~ it as a prize, however, and pike cc

fishing is now a major sport.

even corrode metal.

• A pike said to have been caught in 1497 was alleged to have been 270 years old . This was proven false when it was discovered that the skele­ton was assembled from the vertebrae of other fish .

i o I D .;; (1J

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