SUNFISH

ORDER Perciformes

FAMILY Centrarchidae

GROUP 4: FISH

GENERA Lepomis, Elassoma, etc.

Sunfish are some of the most familiar freshwater fish. They belong to a family that was originally found only in North America but

has now been introduced in Europe and other parts of the world.

KEY FACTS

SIZE

Length: 1 ~-15 in ., depending on

the species.

BREEDING

Sexual maturity: Usually 2 years.

Breeding season: Late spring to

early summer.

No. of eggs: Many thousand.

Hatching time: 2-10 days, de­

pending on the species as well

as the temperature.

LIFESTYLE

Habit: Mainly solitary. Territorial

during the breeding season.

Diet: Insect larvae, crustaceans,

and other small aquatic animals.

Lifespan: 7-8 years.

RELATED SPECIES

The family Centrarchidae contains 32

species of sunfish, crappie, and bass.

They are native only in North Ameri­

ca, but some have been introduced

in other parts of the world.

FEATURES OF SUNFI SH

Bluegill , Lepomis macrochirus: Can be identified by the large dark spot at the rear of its dorsal fin. The breeding male has an orange­red breast and blue on his head and back.

Ear flap: Has a black mark in most sunfish species. The coloring is used for display.

~. MCMXCII IMP BV/IMP INC WILDLIFE FACT FILE'"

Range of sunfish.

DISTRIBUTION

Found in most freshwater areas in the eastern half of North

America, from southern Canada to the Gulf Coast, and in

California's Central Valley.

CONSERVATION

Sunfish are abundant in freshwater habitats throughout their

range, except in places w here industrial pollution has destroyed

the envi ronment.

PRINTED IN U.S.A.

Dorsal fin: Characterized by many stout spines, espe­

cially toward the front.

Pumpkinseed, Lepomis gibbosus: Distinguished by its larg.e size and Ule wavy blue lines on the side of the male's face.

0160200931 PACKET 93

Sunfish are abundant in most freshwater habitats in

eastern North America. The common names of different

species do not always include the word sunfish. Two

familiar sunfish are the pumpkinseed and the bluegill.

The warmouth and the flier are two other sunfish.

~ HABITS Sunfish occur throughout the

eastern half of North America

in weedy ponds, slow-moving

streams, and marshes. A few

species have specialized require­

ments. For example, the black­

banded sunfish lives only in very

acid water in East Coast pine bar­rens (sandy plains with pines).

During most of the year, sun­

fish forage by themselves for

crustaceans and insects. But in

late spring, during the breed­

ing season, several species form

what seem to be nesting colo­

nies, with the males crowding

together in suitably warm, shal­

low water. During the long pe-

riod of inactivity that comes

with winter, a few species gath­

er in small schools.

A number of sunfish species

are fairly brightly colored dur­

ing the breeding season. The

males are usually more colorful

than the females, and they use

their hues to warn rivals away

while creating and defending

their nesting territories. The fe­

males have no need for bright

colors. They visit the nests only

briefly to lay eggs, showing no

further interest in the raising of

their young. Unlike the aggres­

sive males, the females seldom

engage in any sort of combat.

~ FOOD &; FEEDING All species of sunfish feed most-

lyon aquatic insects and crus­

taceans. Many vary their diet

with mollusks and small fish of

other species. At the height of

summer, when oxygen levels in

the water are low and animal

life is scarce, a number of sun­

fish supplement their diet with

the leaves and juicy stems of

aquatic plants.

Left: The female bluegill and non­breeding male lack the bright colors of the breeding male.

DID YOU KNOW? • The Everglades pygmy sun­fish is the smallest member of

the sunfish family. It is never

more than one and one-half

inches long.

• The redear sunfish is very fond of snails and has special

teeth for crushing them. As a

result, many people call this

fish the "shellcracker."

• The black-banded sunfish is not only native to the East but

also common in much of that

area. But when streams and

The pumpkinseed and some

other sunfish may prey on the

young of their own species. The

result of this cannibalism is that

there are often fewer adults in

a pond. But because these sun­

fish have already eaten many of

the fish that might have com­

peted with them for food, they

are usually well fed and larger

than other sunfish species. They

lay more eggs than they might

otherwise. Enough young sur­

vive to maintain the population.

ponds need restocking, the

new fish are imported from

Germany, where this sunfish

is an introduced species.

• The Sacramento perch is the only member of the sunfish

family not found in eastern

North America. It is native to

California's Central Valley.

• Because they are attractive and easy to keep in captivity,

sunfish- especially brightly

colored species-are popular

aquarium fish .

~ BREEDING When the water starts to warm

up in the spring, the male blue­

gill, like most male sunfish, pre­

pares a nest in shallow water

near the shore. He uses his tail

to fan away dead plant matter.

After he has exposed a saucer­

shaped area of sand that is two

to three feet in diameter, he is

ready for the visit of females.

A single female may deposit

as many as 38,000 eggs, and

frequently more than one fe­

male lays her eggs in a nest.

The male fertilizes the eggs be­

fore they drop into the sand.

Left: The pump­kinseed is larger than the bluegill and is less likely to be found in open water. It prefers to stay in weed patches or near underwater logs. It has wavy blue lines with orang ish patches and a bright red or orange spot on the back of its ear flap.

Left: The redear sunfish is wide­spread in the South. It is simi­lar to the blue­gill but can be distinguished by the reddish or orangish patch on its ear flap. One of the local names for this fish is "stump­knocker. II

The bluegill's eggs hatch in

less than a week, but the eggs

of some other species may take

up to 10 days. The male guards

the small fry (young) for a few

days before they drift away to

begin life on their own.

Pygmy sunfish-tiny, colorful

species that live in swamps and

marshes in the Southeast-do

not have the strength to sweep

away dead vegetation for their

nests. Instead, the male uses this

material to build a nest. He then

guards his nest and eggs much

as his larger relatives do.

~ li~ NATUREWATCH It is easiest to see sunfish dur­

ing their breeding season in

late spring or early summer.

At this time the male guards

his nest in the shallow water

of a slow-moving stream or

pond. The nest is usually a

circular area of white or yel­

low sand swept clean of de­

bris. If you watch the nest

long enough, its owner will

appear, ready to drive away

fish that might eat the eggs.

"" CARD 42 AMERICAN PADDLEFISH

ORDER Acipenseriformes

FAMILY Po/yodontidae

GROUP 4: FI SH

GENUS & SPECIES Po/yodon spathu/a

The American paddlefish was thought to be a shark when it was discovered in the 18th century. This strange freshwater fish has a

paddle-shaped snout that is about one-third its total length.

KEY FACTS

~ SIZES

Length: Up to 7 feet.

Weight: Up to 200 pounds.

~ BREEDING

Sexual maturity: 7-8 years.

Breeding season: February to May.

No. of eggs: Several hundred.

Hatching time: 5-10 days.

(5) LIFESTYLE

Habit: Solitary except during the

egg-laying season.

Diet: Insect larvae, planktonic crus-

taceans, and various other small

aquatic animals.

Lifespan: Up to 30 years.

~ RELATED SPECIES

The only other member of the fami-

ly Po/yodontidae is the Chinese stur-

geon, Psephurus g/adius, which lives

in the Yangtze River.

DISTRIBUTION

Found in the drainage systems of the M ississippi and Missouri

rivers, ranging west as far as Montana and south to the Gulf

Coast of Texas, Louisiana, Mississippi, and Alabama.

CONSERVATION

The American paddlefish is declining in most of its range be­

cause of fishing and the effects of dams, the channelization of

rivers, silting, and pollution.

FEATURES OF THE AMERICAN PADDlEFISH

Gill cover: As its name suggests, this large flap covers the gills. It extends from behind the eyes ......... iIIIIC;~E~~_'Y" back into a point.

Tail : The primitive nature of the paddle­fish is evident in the way the backbone extends into the upper lobe of the tail. In most modern fish, the backbone does not go into the tail.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A.

snout that gives the fish its name may be 2 feet or more in length. It is covered with hundreds of taste buds, and these sense organs may help the fish find food .

0160200891 PACKET 89

The paddlefish is found only in deep water in the interior ... ~ BREEDING

of the United States. It is one of the most ancient fish,

having survived from the Age of Dinosaurs. But today

its existence is threatened by overfishing, pollution,

silting, and other consequences of human activities.

~ HABITS The American paddlefish is an

ancient, smooth-skinned rela­

tive of sturgeons. It lives in the

drainage basins of the Missis­

sippi and Missouri rivers and

their tributaries-in the central

United States from the Great

Lakes south to the Gulf Coast.

The paddlefish prefers deep,

slow-moving, and fairly clear

water with gravel on the bot­

tom. In addition to rivers, it is

found in bayous, lakes, and res­

ervoirs. Within its range, this

fish is fairly common in places

where the water is clean. But in

many areas it is threatened by

pollution from industrial chem­

icals and household sewage. In

some places its movement to

and from its breeding grounds

is blocked by dams. Paddlefish

have declined most drastically

in areas where silt has covered

the gravel beds that they need

for spawning.

The paddlefish is also called

the spoonbill and the spoonbill

cat. It is clearly distinguished by

its long, paddle-shaped snout,

but scientists are not sure about

the function of this projection.

It is covered with taste buds, so

it may help the fish in locating

its food.

Above: As the American paddlefish swims along with its huge mouth open water-carrying oxygen and food-rushes in over its gills.

Right: The paddlefish prefers clear water and disappears if there is too much silt.

During most of the year, pad­

dlefish are solitary. But in the

spring-from February in the

South to as late as May in the

North-these fish gather over

gravel beds in deep water. The

females release their eggs, and

the males fertilize them. The

eggs then sink into the gravel,

where they adhere to the first

thing they touch.

Within five to ten days, the

eggs hatch. The young quickly

I )<iJ NATUREWATCH

The paddlefish is rarely seen.

It is difficult to find because

it inhabits deep rivers and

bayous. However, once in

a while, near the surface of

a calm pool, you may spot this strange creature swim­

ming in large circles, with

its mouth w ide open. It has

come up from cooler, deep­

er waters to gather some of

the many small planktonic

animals that flourish in the

warmth of sunlight.

start swimming about, search­

ing for tiny animals to eat.

The transparent young pad­

cllefish does not show any sign

of the paddle-shaped snout at

first, but this distinctive feature

begins to appear within two or

three weeks. If there is a good

supply of food, the young fish

develops rapidly. It may reach a

length of about one foot in its

first year and grow to two feet

in its second year.

~ FOOD &: FEEDING The paddlefish is a filter feeder.

It moves around with its huge

mouth wide open in order to

strain tiny swimming and float­

ing crustaceans and the larvae

of aquatic insects from the wa­

ter. While the fish is swimming,

its gills are held open. Its long

"gill rakers" catch anything that

flows past. Before long, the pad­

dlefish has gathered a throat

full of food. It pauses, swallows

DID YOU KNOW? • The paddlefish lays its eggs on the bottom of deep rivers.

As a result, scientists did not

find its young and begin to

study them until 1933.

• The paddlefish has a skele­ton made of cartilage rather

than bone. Because of this, it

was thought to be a variety of

freshwater shark when it was

discovered in the 1700s.

• The paddlefish may reach

what it has collected, and then

begins foraging again.

Other fish are not part of the

adult paddlefish's normal diet.

Occasionally, however, they are

taken in by accident. They are

then swallowed along with all

the other food the paddlefish

has strained out of the water.

Below: The gill cover of the paddle­fish provides protection for its gills, which are very delicate.

seven feet in length. Its closest

relative, the Chinese sturgeon,

is much larger. According to

unauthenticated reports, this

fish may reach more than 20

feet in length.

• When a paddlefish hatches, it has teeth. The young fish at

first preys on other fish, using

its teeth. But it eventually loses

its teeth and becomes a fi lter­

feeding adult.

JOHN DORY

ORDER Zeiformes

FAMILY Zeidae

GROUP 4: FISH GENUS &: SPECIES Zeus faber

The John Dory's rather grumpy expression comes from its upward-slanting lower jaw. This jaw is actually the fish 's greatest asset because it can extend forward to gulp up unsuspecting prey.

KEY FACTS

SIZES

Length: Average, 10-16 in. Female

can reach 28 in. Larva, )4 in .

Weight: Average, 5-7 lb. Female

can reach 18 lb.

BREEDING

Spawning season: March to May

in the Mediterranean Sea. Varies in

other waters.

LIFESTYLE

Habit: Sol itary or in small schools.

Mainly an inshore fish, sometimes

found close to the seabed in shal­

low water.

Diet: Small fish as well as marine

invertebrates.

RELATED SPECIES

Of the 10 species of dory in the

family Zeidae, only the John Dory

inhabits European waters. The Pa­

cific John Dory, Z. japonicus, is a

close relative.

Range of the John Dory.

DISTRIBUTION

Eastern Atlantic waters, from the coasts of Norway and Scot­

land, to the Mediterranean and Black seas, and south along

the coast of Africa as far as the Cape of Good Hope.

CONSERVATION

Although fished in northern Europe and the Mediterranean,

the John Dory is not in danger of serious depletion. It is quite

rare in the heavily polluted North Sea, however.

FEATURES OF THE JOHN DORY

Coloring: The main color varies considerably from fish to fish . Usually dark yellow or olive brown , of­ten with lighter yellow or white mottling or with wavy lines and a metallic sheen . The large blotch on each side varies from dark yellow to dark brown with a light, often golden, circle around it.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Fin rays: Long, stiff spines in dorsal and posterior anal fins .

movement, the fish can open its mouth wide and swing its lower jaw forward to engulf prey.

PRINTED IN U.S.A.

Body: A flattened, oval shape with a

double set of large spiny scales along

the back and under-side. When the fish

is stalking prey, this oval shape is an advantage

as it presents a thin out­line if seen

head-on.

---.J 0160200811 PACKET 81

The John Dory is found in the Mediterranean Sea

and Atlantic waters off the coasts of Europe and Africa

as far south as the Cape of Good Hope. There are many

stories about this colorful, somewhat grotesque-looking

fish. Some of these tales are legends about the John Dory's

unusual name. Others are myths about the origin of the

large, round spot on each side of the fish 5 body.

~ HABITS The john Dory generally lives

close to the shore, at depths of

30 to 160 feet. In shallow water

it may live near the seabed, but

in deeper water it stays near the

~ FOOD &: HUNTING The john Dory feeds on small

fish like sand smelts, sardines,

sprats, and young herring. It

also eats cuttlefish and squid.

Although it swims slowly, the

john Dory is an efficient preda­

tor. Because of its laterally flat­

tened shape, this fish is able to

weave in and out of the reeds,

surface. This fish is not a strong

swimmer, and it moves slowly

among rocks and weeds. It is

usually solitary but sometimes

joins a small school.

stalking its prey without being

spotted from the front. Then,

with a quick jerk, it speeds for­

ward, opens its protruding jaws,

and engulfs its victim, drawing

it in with an inflow of water.

This strategy of slow stalking

and sudden movement is usu­

ally successful.

~ BREEDING The john Dory breeds during

the spring in the Mediterranean

Sea and during the summer in

more northern waters. It rarely

breeds in the parts of its range

that are farther north than the

Irish Sea; instead, it migrates

south to warmer waters.

The female does not attach

her eggs to a rock as many fish

do. Instead, the eggs float freely

on the waves. Each egg is kept

Left: The pattern of wavy lines on the John Dory's body camouflages the fish against rocks.

Right: The long, spiny rays in the John Dory's dorsal fin look almost like stiff feathers.

I DID YOU KNOW? • According to legend, Saint

Peter once took a gold coin

from the mouth of a john Do­

ry to give to the tax collector.

The dark spots on each side

of the fish are said to repre­

sent the apostle's fingerprints.

The john Dory is sometimes

called Saint Peter's fish as a

result of this story.

buoyant by a tiny bubble of oil

inside it. After hatching, the lar­

vae drift in open water and feed

on plankton.

A young fish usually leaves the

area where it hatched but comes

back yearly to spawn. As the fish

ages, however, it tends to re­

main near its spawning ground.

Right: With only its bulging eyes sticking out, the John Dory is hard to spot head-on.

II "Dory" is derived from the

French name for this fish, do­ree (meaning "golden"). The

English called it the dory until

the 1 700s, when a French pi­

rate nicknamed john Dory be­

gan attacking English ships at

sea. Fishermen were soon call­

ing the fish the john Dory, and

the name stuck.

~ CHARACTERISTICS The john Dory belongs to a very

large group of fish called spiny­

finned fish. Most fish have rays (structures like bones) in their

fins to provide strength. Spiny­

finned fish have very strong fin

rays called spines. Some of these

fish also have spines running

along the body.

Nine or ten long, heavy, fan­

like spines emerge from armored

scales at the base of the john Do­

ry's dorsal fin . There are three or

four similar spines in the posteri-

Left: The John Dory's lower jaw is hinged, so it can swing forward.

or anal fin. A double set of large,

spiny scales runs around the bel­

ly and back, making the fish hard

to attack.

The john Dory appears oval­

shaped when viewed from the

side. But from the front, this tall,

narrow fish looks like a thin strip

with large eyes bulging out at

the sides. Its body has a metal­

lic sheen and a dark blotch sur­

rounded by a pale ring on each

side. The fish has a large head

and an upward-slanting lower

jaw, which it can open wide

and extend far forward.

PUFFER FISH

ORDER Tetraodontiformes

FAMILY Tetraodontidae

GROUP 4: FISH

Puffer fish have an unusual but effective defense against their enemies. They inflate themselves with water or air like balloons

so that they become almost impossible to swallow.

KEY FACTS

SIZE

Length: Largest (the smooth

puffer), over 3 feet.

BREEDING

Eggs: Released along with sperm

near seabed.

Larva: Free-swimming in open wa­

ter for up to 3 months.

LIFESTYLE

Habit: Solitary. Usually slow swim­

mers in sheltered fresh, brackish,

or salt water.

Diet: Hard-shelled crustaceans and

mollusks; also worms and corals.

RELATED SPECIES

There are more than 100 species of

puffer fish in the family Tetraodon­

tidae. Other groups in the order

Tetraodontiformes include the por­

cupine fish, trigger fish, box fish,

cowfish, and oceanic sunfish.

Range of puffer fish .

DISTRIBUTION

Found throughout the world in tropical fresh and salty waters .

Puffer fish live primarily on coral reefs but may be swept into

temperate waters by ocean currents.

CONSERVATION

Although they are regarded as a table delicacy in Japan, puffer

fish have very little economic value and are not threatened by

direct exploitation.

THREE SPECIES OF PUFFER FISH

Oceanic puffer fish: One of the faster-swimming species. Dark blue on top. gray underneath, with black spots on sides. Tiny spines buried in

Skin: Tough and often prickly.

the th roat and belly. Lives near the su"r ~-~~~=~!!'~;=! face of warm seas worldwide. ....

Band-tail puffer fish : Dark brown on top , pale below, with large dark blotches. Slender,

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILE'M PRINTED IN U.S.A

and anal fins set fairly far back on the body. Puffer fish do not have

pelvic fins.

Marbled puffer fish (inflated): Marbled brown

on top with pale belly.

0160200981 PACKET 98

Puffer fish are the enemies of coral reefs, because they have

extremely powerful jaws that are capable of crunching

through the rocky coral heads and devouring the soft

polyps within. These fish are apparently immune to the

venom that is contained in the stinging tentacles of corals.

In fact, a puffer fish possesses its own poison-which

is one of the most virulent of all natural toxins.

~ HABITS Puffer fish are found throughout

the tropics in oceans as well as

in fresh and brackish water. Be­

cause they are poor swimmers,

most species live in coastal shal­

lows among weed beds or coral

reefs that provide shelter from

strong currents.

Most fish propel themselves

through sinuous body and tail

movements. But a puffer fish

sculls through the water, wav­

ing its large dorsal and anal fins

from side to side. It steers with

its tail and paddles with the pec­

toral fins near its head.

Although not fast, this meth­

od provides great maneuver-

ability. With a flick of its fins, a

puffer fish can move up, down,

forward, or backward, slipping

into a rock crevice at any sign of

danger. If no cover is available, it

resorts to the defense tactic that

gives it its name.

At the slightest alarm, a puffer

fish blows itself up by drawing

water into a sac that is joined to

its stomach and retaining the

water with muscular valves. If it

is pulled out of the water, it fills

the sac with air. Even if a preda­

tor manages to swallow a puf­

fer fish, its triumph is short-lived,

since the puffer possesses a le­

thal nerve poison.

~ BREED I NG Many puffer fish are very territo­

rial. Each male stakes a claim on

an area of the reef and defends

it vigorously against fish of the

same species. The female may

defend a smaller territory, but

this may be contained within a

male's domain. In this way one

male may control and breed

with several females .

The male and female release

sperm and eggs near the sea­

bed . They rely on currents to

Left: Instead of fleeing from a pred­ator, a puffer fish gulps water and inflates itself in defense.

I DID YOU KNOW? • A puffer fish has the same

poison as the blue-ringed oc­

topus, one of the most dead­

ly marine animals. Despite

this, puffer fish flesh is a deli­

cacy in Japan known as fugu. The cook is specially trained

in removing the poisonous

parts, but cases of fatal fugu

poisoning occur.

•

bring them together for fertiliza­

tion. Some species attach the

fertilized eggs to rocks . Others

- like the common puffer fish, a

Southeast Asian freshwater spe­

cies-have the males guard the

fertilized eggs until they hatch.

The tiny larval fish that hatches

from the egg is able to inflate its

body in defense almost as soon

as it emerges. It swims into open

water, drifting for several weeks

before settling on a reef.

Right: Many puffer fish have bright warning colors, clearly advertising that they are poisonous.

• The oceanic puffer fish is a

stronger swimmer than most

puffers and can attack fast­

moving prey such as squid .

But currents may still sweep it

north into European waters.

• Puffer fish that are inflated

with air are often attacked by

birds as they float on the sur­

face of the water.

~ FOOD &: FEEDING The family name of puffer fish­

Tetraodontidae-means "four­

toothed ." These fish's teeth are

fused into four plates, two in the

upper jaw and two in the lower.

Each plate has a sharp edge and

anvil-like crushing surface. The

combination allows puffer fish

to bite through hard substances

such as shell, bone, and rock.

Puffer fish's primary prey are

hard-shelled animals that live on

the seabed, including mollusks,

crustaceans like crabs, and echi­

noderms such as sea urchins.

Left: Most puffer fish are too slow to catch swimming prey, but they may feed on drifting injured fish .

Left: The four tooth plates that make up a puffer fish 5 "beak" are very tough. The fish can gnaw its way through shell, bone, or even coral rock to find food.

These creatures rely on their ar­

mor for protection, and many

are not very mobile. They can­

not escape even a slow-moving

puffer fish, which can crunch

through their shells.

A puffer fish can also devour

a coral reef, gnawing through

the hard coral rock and the soft,

anemonelike polyps. Using its

grindstone teeth, it pulverizes

chunks of coral, reducing the

coral to a sandy pulp--which it

then swallows. After digesting

the edible bits, the puffer fish

ejects the rest. It appears to be

immune to the venom released

by the coral's stinging cells.

LESSER SPOTTED DOGFISH

ORDER Carchariniformes

FAMILY Scyliorhinidae

GROUP 4: FISH GENUS & SPECIES Scy/iorhinus caniculus

The lesser spotted dogfish is a harmless bottom-living shark that feeds on easy prey such as crabs and whelks. It tracks

them down with the aid of its highly developed senses.

KEY FACTS

SIZES

Length: Usually 2-2~ ft. Some­

times 3~ ft. Weight: Up to 4 lb.

BREEDING

Sexual maturity: At a length of

about 20 in.

Mating season: Mainly fall.

Fertilization: Internal.

Eggs: 18-20, each contained in a

horny protective capsule.

Development time: 5-11 months.

LIFESTYLE

Habit: Mainly bottom-dwelling.

Solitary or in schools.

Diet: Small, slow-moving seabed

animals, especially mollusks and

crustaceans.

RELATED SPECIES

There are about 60 species in the

dogfish family worldwide. Close

relatives include the swell shark,

Cephaloscyl/ium ventricosum.

Range of the lesser spotted dogfish.

DISTRIBUTION

Found in coastal waters of the eastern Atlantic from Scandi­

navia to northwestern Africa, including the North Sea, Irish

Sea, English Channel, and Mediterranean.

CONSERVATION

The lesser spotted dogfish is common throughout its range

and is not thought to be threatened.

1 HOW THE LESSER SPOTTED DOGFISH MATES

Female: Once mating is complete, she will swim into shallow water to begin laying eggs.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Male: When mating, he coils his body around the female and inserts one of his claspers (reproductive or-gans) into her cloaca (genital open­ing). He injects sperm via the clasper so that internal fertilization can occur.

PRINTED IN U.S.A.

Skin: Covered with thou­sands of tiny toothlike scales called dermal

0160200861 PACKET 86

The lesser spotted dogfish seems to have changed very little

over millions of years. This is probably because it was so

well suited to its way of life that further evolution was not

necessary. This dogfish possesses an acute sense of smell

as well as a unique system of electrical sensors--features

that enable it to detect prey with deadly accuracy.

~ HABITS The lesser spotted dogfish is a primitive small shark. This dog­fish has changed very little since the Mesozoic era over 65 million years ago. Other sharks evolved into specialized forms, but this species kept the form and prob­ably the habits of its ancestors.

Many sharks are swift ocean hunters, but this fish swims very slowly along the seabed, sniff­ing for food among rocks and weeds. It is most common in shallow water down to 500 feet,

and it frequently comes inshore to feast on the rich food supplies near the low tidemark. Young dogfish tend to live closer to the shore, and newly hatched fish are even found in rock pools, stranded by the receding tide.

The lesser spotted dogfish is common throughout European waters. It frequently swims in schools, often of one sex.

Right: The lesser spotted dogfish is the most common shark species in European waters.

~ BREEDING To breed, most fish eject huge numbers of eggs or sperm in­to the water and rely on chance to bring them together. Only a very small fraction of the fertil­ized eggs develop into mature fish . In contrast, the lesser spot­ted dogfish produces only 18 to 20 fertilized eggs and goes to great lengths to ensure that both eggs and young survive.

During mating, the male uses one of his claspers (reproductive organs) to inject sperm into the female's cloaca (genital open­ing). This ensures that the eggs are properly fertilized. The mat­ing act involves much maneu­vering by the male as he coils

Left: The lesser spotted dogfish uses its keen sense of smell to find prey on the seabed.

DID YOU KNOW? • The filaments on the lesser spotted dogfish's egg capsule may be up to three feet long when extended. But they curl up to less than six inches. • As the dogfish embryo de­velops, it makes swimming movements inside its capsule.

his long body around his mate. Following a gestation of sev­

eral weeks, the female produces her eggs, each contained in a rectangular capsule with coiled filaments extending from each corner. The filaments get en­tangled in seaweed, anchoring the capsule for 5 to 11 months, while the embryo develops in­side. During this time, the em­bryo obtains nourishment from the large yolk sac.

When it hatches, the young dogfish is approximately four inches long and almost fully de­veloped, but it still carries the remains of the yolk sac. Before long it can hunt for itself.

Right: The embryo can be seen through the capsule's translucent walls. It feeds off the large egg yolk.

This pumps water-and thus oxygen-through the perme­able walls of the capsule. • This dogfish's skin is cov­ered with thousands of tiny toothlike structures called der­mal denticles. They make the skin rough like sandpaper.

121 NATUREWATCH The egg capsules of the lesser spotted dogfish often wash up on the beach. Known as mer­maid's purses, they are pale brown, flexible, and almost clear when fresh . They darken and get more fragile with age.

~ FOOD & FEEDING The lesser spotted dogfish gen­erally feeds on the seabed. It searches for slow-moving prey such as crabs, shrimp, bottom­dwelling fish, marine worms, and sea snails. Although most sharks have sharp teeth, this species has small, thick teeth that are specially adapted for crushing the shells of mollusks and crustaceans.

Like all sharks, the lesser spot­ted dogfish has an acute sense of smell. This sense is especially

The egg capsules produced by different members of the dogfish family vary. The egg capsule of the nursehound is four inches long, for example, twice as long as the capsule of the lesser spotted dogfish.

valuable in the shallow waters that the fish prefers, where the currents and waves stir up sedi­ment from the bottom, making the water almost opaque.

This dogfish also has electri­cal sensors on its snout. At very short distances, they can detect the minute voltages generated by the nervous systems of prey animals. So even if the water is cloudy and the scent trail poor, the dogfish can find prey with its electrical sensors.

PORCUPINE FISH

ORDER Tetraodontiformes

FAMILY Diodontidae

GENERA Diodon, Chilomycterus, etc.

Porcupine fish are slow-swimming inhabitants of the coral seas. They defend themselves from their enemies by their startling

ability to turn themselves into balls of bristling spines.

KEY FACTS

SIZES Length: Usually about 1 ft. Can

reach up to 3 ft. Spines: Up to 2 in.

BREEDING

Details are unknown, but the fish

probably shed eggs and sperm in

open water. The eggs hatch into

well-developed young.

LIFESTYLE

Habit: Solitary. Usually inhabit

coral reefs.

Diet: Mollusks, hard corals, and

marine worms.

RELATED SPECIES

There are about 15 species of por­

cupine fish, including the spotted

porcupine fish, Diodon hystrix; the

balloonfish, D. holocanthus; and

the bridled burrfish, Chilomycterus

antennatus. All are closely related

to the 118 or so puffer fish species

in the family Tetraodontidae.

Range of porcupine fish .

DISTRIBUTION

Found throughout the world in tropical waters. They live main­

lyon coral reefs but are sometimes swept into temperate wa­

ters by ocean currents.

CONSERVATION

Although some species are regarded as a food delicacy in Ja­

pan, porcupine fish have very little economic value. They are

not threatened by direct exploitation.

DEFENSES OF PORCUPINE FISH

Bridled burrfish, Chilomycterus antennatus, is shown here.

Deflated: When in no danger, the fish swims with its spines relaxed and flat against its body.

Coloration: Most species are pale with dark markings.

Inflated: When disturbed, the fish pumps its stomach full of water until it reaches full capacity.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Spines: Modified scales. Fixed in some species

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and movable in others.

Fins: Small and weak. Porcu­pine fish are poor swimmers

and cannot swim against cur­rents. However, they are agile

and can maneuver into any position while hovering

in one spot.

Head: Blunt and rounded . Beaklike mouth contains a

solid tooth plate in each jaw that can bite through coral

rock and mollusk shells.

0160200841 PACKET 84

Swimming along weakly with their spines relaxed, porcupine

fish may look like easy prey to large marine predators. But

looks can be quite deceptive. Porcupine fish are actually

extremely dangerous. Even formidable hunters such as

sharks and barracudas have been found dead with

puffed-up porcupine fish stuck in their throats.

~ HABITS Porcupine fish are natives of

the coral seas, although they

can be found in warm waters

worldwide. These fish are weak

swimmers, so if one strays into

a strong ocean current, it may

be swept along for quite a dis­

tance. Sometimes it even turns

up on the coast of Europe, far

from its tropical home.

Its poor swimming ability al­

so means that a porcupine fish

cannot flee from attack. Instead,

it uses the same defense meth­

od as a puffer fish. It inflates it­

self into a floating sphere that

is covered by fearsome spines.

Up to two inches long, these

spines bristle just like the quills

on a porcupine.

The spines make porcupine

fish almost impossible to swal­

low. Even if a predator succeeds

in devouring one of these fish,

the internal damage inflicted

by the spines is often fatal.

In addition to its spines, a

porcupine fish possesses pow­

erful toxins in its skin and liver.

These poisons help protect it

from predators.

Right: When swimming in safe wa­ters, a porcupine fish's spines lie flat against its body.

DID YOU KNOW? • The inflated skins of porcu­pine fish are dried and sold as

curios in the Far East. Some

I are turned into grotesque lan­

terns with electric light bulbs

on the inside.

• On some Pacific islands the dried skins of porcupine fish

~ BREEDING The spawning habits of porcu­

pine fish have never been stud­

ied, but they probably resemble

those of puffer fish. These close

relatives eject eggs and sperm

into the water in large quantities

and rely on close proximity to

bring about fertilization.

The eggs of puffer fish hatch

on the seabed. The tiny but well­

developed young are able to in­

flate their bodies almost as soon

as they emerge.

Left: Even a partially inflated por­cupine fish is a difficult target for a marine predator.

Right: Porcupine fish puff up by swallowing water until they be­come perfect spheres.

were once used for making

war helmets.

• The spines of porcupine fish are actually highly modified

scales. They have "roots" that

interlock at the base, forming

a flexible armor that is similar

to spiny chain mail.

Left: One of the 15 or so species of porcupine fish is the bal­loonfish or spiny puffer fish. This spe­cies is marked with distinctive

black patches.

~ FOOD & FEEDING Porcupine fish are among the

few fish that feed on coral, un­

deterred by its hard limestone

armor. They nip off its branches

and then crush the coral to a

gritty pulp before swallowing.

Porcupine fish digest the cor­

al's soft, edible parts, but the

pulverized limestone may ac­

cumulate in their stomachs be­

fore being ejected. One fish had

a pound of crushed coral rock

in its digestive system when it

was caught.

These fish also eat mollusks

like oysters and clams, crunch­

ing the thick shells with ease.

HAMMERHEAD SHARK

ORDER Carcharhiniformes

FAMILY Carcharhinidae

GENUS Sphyrna

GROUP 4: FISH

Hammerhead sharks are named for the unusual shape of their heads. These predators hunt fish by smell and taste as well as

by sensing tiny electrical changes produced by their prey.

SIZES

Length: Average, 13 ft. But some

species can grow to 20 ft. Weight: 1 ton .

BREEDING

Sexual maturity: Thought to be

10-15 years.

Mating season: Probably spring

and early summer.

Gestation: Up to 20 months.

No. of young: Up to 40.

LIFESTYLE

Habit: Feeds alone at night. lives

in schools during the day.

Diet: Fish and invertebrates.

lifespan: Thought to be 30 years

or more.

RELATED SPECIES

There are 8 species of hammer­

head shark in the genus Sphyrna.

They include the great hammer­

head, the scalloped shark, and the

smooth hammerhead.

Range of hammerhead sharks.

DISTRIBUTION

Found in oceans all over the world except for very cold regions.

Hammerhead sharks are rarely found where water temperatures

are below 68° F.

CONSERVATION

It is difficult to establish any population figures for hammerhead

sharks because they are migratory. However, these fish are not

thought to be endangered.

FEATURES OF HAMMERHEAD SHARKS

(

Great hammer­head, Sphyrna mokkarran: Forward edge of hammer is straight in the adult.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Scalloped ham­merhead, Sphyrna /ewini: Small sec­ond dorsal fin, black tips on pectoral fins. Scalloped head.

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/ '

Head: T-shaped. Eyes located at hammer tips, with nostrils set

slightly farther in.

(

Smooth hammer­head, Sphyrna zygaena: Over 12 feet long. Head lacks central in­dentation.

0160200961 PACKET 96

Hammerhead sharks are generally about 73 feet long.

However, some species can grow as long as 20 feet. The

flattened heads of these strange-looking fish are thought

to act like natural hydrofoils, stopping the sharks from

pitching and rolling from side to side as they swim.

~ HABITS Like most sharks, hammerheads keep moving in order to breathe because they cannot draw water over their gills. They create a cur­rent over their gills by moving forward. As water flows through them, the gills extract oxygen.

Some sharks spend most of their lives lurking in the depths, but hammerheads regularly sur­face. Their head shape may help them rise through the water.

Hammerhead sharks feed only

at night. During the day, when they are at rest, they tend to form schools of up to 100 indi­viduals, most of them females.

The eight species live world­wide, but the scalloped ham­merhead is the most common. All the species migrate in large schools twice a year. At the be­ginning of summer, they move from the equator to cooler wa­ters. They make the return jour­ney when winter sets in.

DID YOU KNOW? • The cells of a hammerhead shark's retina contain guanine -a silvery substance that may help it to distinguish shapes in dim light.

• Hammerhead sharks have

~ FOOD & HUNTING Although hammerhead sharks swim in schools during the day, they hunt alone at night. They feed primarily on invertebrates and fish, with a preference for stingrays. These sharks use their strong teeth to tear larger prey apart but do not chew. Instead, they swallow big chunks of food whole and break them down in their stomachs.

With its eyes set at either end of its elongated head, a ham­merhead shark has fairly poor vision. This might seem a disad­vantage for a predator. But this shape may increase a hammer­head's senses of smell and taste and its electrosensitivity.

Left: In some parts of the world, hammerheads are killed for their meat and liver oi/.

Right: If a hammerhead shark is threatened, it uses its sharp teeth to defend itself.

been reported to devour their own species.

• There is no single accepted theory to explain the charac­teristic head shape of a ham­merhead shark.

Hammerhead sharks complete their mating in summer. The fe­males carry the soft-shelled eggs internally. The embryos are ini­tially nourished by the egg yolk and later by the mother, since the yolk sac connects directly to her bloodstream.

Depending on the size of the female, there can be up to 40

Left: The scal/oped hammerhead is easier to distinguish than many of the other species.

Left: The eyes ofahammer­head shark are positioned at opposite ends of its flattened head.

pups (young) in a litter. Before they are born, the pups have soft teeth that cannot damage the egg. The "hammer" flaps on their heads are folded back to streamline them for birth.

When a pup is born, its egg tears open and the umbilical cord, connecting the pup to the yolk sac, breaks. The pup comes out headfirst. It has a scar on its underside much like the navel ofa mammal.