FLYING FISH GROUP 4: FISH

... ORDER ~ FAMILY ~ Cyprinodontiformes "'1IIIIIIII Exocoetidae

GENERA Exocoetus, Thoracopterus, Fodiator, etc.

Flying fish have an extraordinary way of escaping from enemies. They accelerate across the ocean surface like a seaplane, then

spread their fins and glide above the water to safety.

KEY FACTS

SIZES Length: Up to 18 in. (California

flying fish) . Weight: Up to 1 ~ lb.

BREEDING Mating season: Spring and early summer in warm and temperate waters. Eggs: Free-floating in oceanic species. Filaments on eggs of shallow sea species catch in floating vegetation or debris.

LIFESTYLE Habit: Sociable, but does not swim in tightly organized schools. Diet: Small planktonic animals, including the larvae of other fish.

lifespan: Unknowri.

RELATED SPECIES There are about 48 species of flying fish of various genera worldwide. The most closely related species are the tropical halfbeaks and the needlefish.

FEATURES OF FLYING FISH Tail: Enlarged , powerful lower lobe. Used to build up momen­tum that allows fish to clear the water.

Fins: Large pectoral fins fold back along body when swim­ming and spread out rigidly when "flying." Pelvic fins are also large in

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Range of flying fish .

DISTRIBUTION

Flying fish occur in theyopical zones of all the major oceans. The Atlantic flying fish often moves into northern waters

around Europe and North America in late summer and leaves when the water cools in early winter.

CONSERVATION Although the California flying fish has some commercial

value as bait for game fishing, no species is in direct danger.

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HOW A FLYING FISH GLIDES THROUGH THE AIR

1. Approaches surface of the water at an angle, vibrating tail to build up momentum.

2. Spreads fins and glides for several feet.

3. As a flying fish loses momen­tum, it may touch its tail down in the water, regaining propulsion to continue its flight.

0160200441 PACKET 44

Flying fish live mainly in tropical oceans, where

they are favorite targets of predators such as tunas,

sharks, and seabirds. Their celebrated skill in the

air often helps them escape underwater attackers.

But their prowess at "flying" may carry them away

from one enemy, only to deliver them into the

jaws of an airborne predator.

~ HABITS While feeding in surface wa-ters, flying fish are targets for tuna and bonito, which hunt in packs in warm seas. To es­cape these predators, flying fish leap out of the water and glide over the ocean surface.

Their "wings" are large pec­

toral fins and, in some species, pelvic fins. The fins are usual­ly folded back along the fish's flanks. But when it "flies," the fish holds its fins out stiffly, like airplane wings.

As it propels itself through the water, a flying fish builds up momentum until it can glide through the air.

As it breaks the surface, the fish speeds up by vibrating

the lower lobe of its tail fin in the water. Then it spreads its "wings" and glides clear of the waves for several seconds before touching down.

The average "flight" lasts two to three seconds, but longer flights are common, sometimes lasting 10 seconds and covering over 30 feet. While flying is an ideal way of escaping from predatory tuna, it puts the fish in jeop­ardy from ocean birds such as the albatross and frigate bird, which snatch flying fish as they leap from the water.

Right: Flying fish are most common in tropical waters, despite the scarcity of food.

~ BREEDING In the Mediterranean, the At-lantic flying fish spawns from May to July. The eggs are cov­ered with fine threads, or fila­ments, that anchor them to floating objects so they do not sink to the seabed.

All coastal species of flying fish have similar eggs. But the eggs of open sea species have much

Left: By flicking its tail back into the water, a flying fish can con­tinue its flight for some time.

DID YOU KNOW? • When accelerating for take­off, a flying fish vibrates its tail at a rate of over 50 beats per second.

• A record flight of 42 sec­onds covered 2,000 feet.

• Some marine predators, like dolphins, outwit a flying fish by swimming along its

shorter filaments that act like parachutes, slowing down the eggs as they sink in the water. The eggs hatch while sinking, and the larvae drift back to the surface to feed on plankton.

Unlike their parents, young flying fish are often brightly colored, with shorter pelvic and pectoral fins and a long barbel trailing from the chin. In one species the barbel is longer than the body of the young fish .

path at high speed. When the fish reenters the water, the predator is waiting for it.

• Flying fish have been found on ship decks over 30 feet above sea level. They may reach this height by taking off into the wind and being swept up by air currents.

Above: A flying fish uses both pectoral and pelvic fins to power its "flight."

Left: A flying fish clears the water easily as it glides, escaping underwater enemies.

~ FOOD & FEEDING Most flying fish live in the warm oceans of the tropics, where they eat zooplankton -tiny floating animals such as copepods and the larvae of crabs and fish.

Flying fish gather in areas where currents carry nutrients up to the surface waters. The nutrients are eaten by zoo­plankton, which in turn are eaten by flying fish.

Flying fish feed in the upper parts of the ocean, where plankton is densest. They strain water through their gill rakers to filter out edible par­ticles. Larger plankton eaters such as whale sharks may join the flying"fish when feeding.

BASKING SHARK

ORDER Lamniformes

FAMILY Cetorhinidae

GROUP 4: FISH GENUS &: SPECIES Cetorhinus maximus

The basking shark may look more fearsome than its smaller, more fierce relatives. But despite its cavernous mouth and huge

dorsal fin, it is a placid, harmless giant.

KEY FACTS

SIZES Length: Averages 25-30 ft. Weight: 4-4Y.1 tons.

BREEDING Sexual maturity: 2-4 years. Mating season: Spring in the North Atlantic . Gestation: May last 3 years. No. of young: 1, occasionally 2.

LIFESTYLE Habit: Occurs singly, in small groups, or in schools. Slow­moving; often appears at the surface. Diet: Plankton. lifespan: Not known.

RELATED SPECIES The basking shark is in a family by itself. But it is related to thresher sharks and mackerel sharks.

Range of the basking shark.

DISTRIBUTION

Found in temperate waters in both the northern and southern hemispheres.

CONSERVATION

The basking shark is thought to be low in numbers, but there are no accurate details about population figures. There is some concern that fishing may be reducing the basking shark's feeding areas.

SPECIAL ADAPTATIONS OF THE BASKING SHARK

Gill rakers: Sticky, mucous­covered bristles trap food.

Filament: Thin layers of orange-red flesh that absorb

en from the water.

Feeding: Water, oxygen, and plankton are sucked into the mouth and filtered through the gill rakers. The rakers trap the food but allow the water and carbon dioxide out through the five gill slits on each side of the mouth.

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

Gill rakers

Filament

0160200401 PACKET 40

cruising near the surface of temperate oceans

with its giant mouth wide open.

Despite its huge size-up to 30 feet-it feeds

only on tiny sea creatures that it filters

from the water.

~ FOOD & FEEDING Sharks are renowned as fierce predators. Yet the two largest species, the basking shark and the whale shark, have a com­pletely different feeding be­havior. Like manta rays and great baleen whales, they sustain their enormous bulk by swallowing great quantities of plankton-tiny ocean creatures that include fish eggs, cope­pods, and arrow worms.

By cruising gently through the ocean with its great mouth

yawning open, the basking shark draws in tons of water. The water passes out through five wide gill slits on each side of the shark's neck after it has been strained through rows of gill rakers. Thousands of these mucous-covered bristlelike structures lie next to the gills. Each is about four inches long. When the basking shark opens its mouth, the gill rakers spring up to form dense fringes that trap the tiniest prey.

The basking shark is known for cruising slowly. It rarely swims faster than three miles an hour and is often seen at the sur­face of the water. It is named for its habit of lying still-its back breaking the surface and its great dorsal fin protrud­ing-as if it were basking in the sun. Although they are often seen alone or in twos and threes, basking sharks sometimes gather in schools of 50 or even more than 100

individuals. Basking sharks are seen

most often in summer, when temperate waters are rich in plankton. In winter this food supply dwindles, and it is thought that the sharks can­not take in enough plankton to remain active. Instead, they may retreat to deeper water or

DID YOU KNOW? • The basking shark is the second-largest fish in the world after the whale shark.

• The largest basking sharks on record include a 39-foot specimen trapped in a net off southeast Canada in 1851, another 39-foot shark caught off Portugal in 1865, and a 45-foot giant caught off Norway in the 1890s.

• Cruising at about 2 knots, a basking shark can filter 1,000 tons of seawater through its mouth in an hour.

l eft: The basking shark is a gentle giant of the ocean.

Front cover inset: The basking shark's wide, gaping mouth acts like an enormous sieve.

possibly the sea floor. There they lie still and stop feeding . Their metabolic rate drops, and they rely on deep currents to bring oxygen to their gills. In European waters basking sharks appear to shed their gill rakers in winter, making feeding impossible. By spring, when plankton starts to flour­ish again, they have acquired new gill rakers.

~ NATUREWATCH Basking sharks are summer visitors to both the Atlantic and Pacific shores of North America, in coastal and offshore waters. They start to appear in late April and early May, when marine copepods, a staple food, are

• There are reports of basking sharks leaping completely out of the water. They may have been trying to drive off parasites, such as lamprey, attached to their bodies.

• Basking sharks have never been major fishing prey. But some have been fished off Ireland, Scotland, and Norway. The liver from a single shark can weigh 1,500 pounds and yields valuable oil.

~ BREEDING Little is known about the breeding behavior of the basking shark. It IS known, however, that egg pro­duction is strikingly different from that of most sharks.

Sharks generally produce a small number of large eggs. But a female basking shark

may produce six million eggs that are 0.02 to 0.2 inches in diameter. Fertilization is in­ternal, and the young seem to develop inside the moth­er's body, as in most sharks. Why the female produces such a huge number of eggs is unclear. It may be that the

abundant near the surface. By the end of November,

the basking sharks have dis­appeared, probably to deep water for a long winter fast.

The tall dorsal fin and the sheer size of a basking shark make it easy to recognize.

Above: To nourish its huge body, the basking shark spends a large amount of time feeding near the surface of the water.

mass of unfertilized eggs provides nourishment for the developing embryos.

The end result is only one or two offspring. At birth, basking sharks are already about five feet long. Im­mature sharks can grow up to 15 feet. At this stage the

sharks have long, fleshy snouts, with a curved hook at the tip. Basking sharks generally reach sexual ma­turity when they are 15 to 20 feet long.

Below: A system of gill rakers en­sures that no food escapes the basking shark's mouth.

"" CARD 33 RUDD ~~ ___________________________________ G_R_O_U_P_4_:_F_IS_H __ ~ .. ORDER ... FAMILY .. GENUS &: SPECIES ~ Cypriniformes ~ Cyprinidae ~ Scardinius erythrophthalmus

The rudd is a resilient, adaptable fish that thrives under the most difficult of conditions. It often appears as if by magic in the

seemingly barren waters of newly flooded quarries.

KEY FACTS

SIZES

Length: Average, 6-12 in.

Weight: Average, 1 lb .

BREEDING

Sexual maturity: 2-3 years.

Spawning: April to June.

Eggs: ~o in., round. They stick to

vegetation .

Hatching period: 8-15 days.

LIFESTYLE

Habit: Surface-feeders. Swim in

small schools.

Diet: Crustaceans, aquatic insects,

flying insects that land on water,

some plant matter.

lifespan: Up to 10 years.

RELATED SPECIES

A member of the carp family, its

nearest relative is the very similar

roach, Rutilus ruti/us.

HOW THE RUDD FEEDS

Range of the rudd.

DISTRIBUTION

Basically a European species, the rudd is found from Ireland

and southern England through France, Italy, and Greece to

western Siberia and north to Sweden.

CONSERVATION

The rudd is not threatened, either directly or indirectly. It is a

very resilient fish and can survive in waters with relatively high

levels of organic pollution.

Surface feeding: The rudd 's sharply angled mouth allows it to feed on in­sect larvae that float on the surface of the water.

Spawning: Between April and June the rudd lays sticky, mucus-covered eggs that float downstream and be­come attached to water plants.

position of its mouth, the rudd can take food from the bottom

. only when swim­ming vertically.

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The rudd is a small surface-feeding member

of the carp family. Like all of its relatives, it can survive

in large, slow rivers and lowland lakes that contain

little oxygen and are often polluted with fertilizers.

In these waters, the rudd is a major predator of

insects and other small aquatic animals.

Basically a still-water fish, the

rudd is found in lowland lakes,

ponds, and river backwaters. It

is especially common in man­

made lakes and channels such

as flooded gravel pits and drain­

age ditches. These waters are

usually rich in plant nutrients

like nitrogen and phosphorus

that come from decaying plants

and animals or from fertilizers

washed off of adjoining farm­

land. The plant nutrients pro­

mote lush growths of water

plants on which the rudd feeds.

As a result, these neglected,

overgrown waters often teem

with rudd.

The abundant plant nutrients

also help to create clouds of mi­

croscopic floating algae. When

the algae die and rot, the de­

caying action of organisms like

bacteria can use up a great deal

of oxygen in the water. While

many fish become ill or die in

such conditions, the rudd is

able to feed and thrive.

The rudd can also survive in

waters where the food supply is

inadequate for most fish. Small,

depleted lakes in soft-water areas

often harbor large schools of ap­

parently half-grown rudd, whose

growth has been stunted by

poor nutrition.

~ FOOD & FEEDING Although the rudd eats some

plants, it feeds mainly on insects

and small aquatic crustaceans

such as freshwater plankton.

The rudd usually feeds in mid­

water or near the surface. On

hot summer days large schools

of rudd can be seen just be­

neath the surface preying on

Left: The rudd can be identified by its protruding lower jaw.

~ ENEMIES In lowland lakes the rudd preys

on insects and other small wa­

ter animals. In turn, it is preyed

on by larger fish such as perch

and pike. Rudd are most vulner­

able when young. While barely

mobile, a large proportion of

young, called fry, are eaten by

other fish. When they grow big­

ger, rudd are harder to catch.

Since they are surface feeders,

rudd are easily seen from above

by fish-eating birds such as the

heron. The rudd that colonize

gravel pits provide a steady

source of food for the great

crested grebe. Small rudd in

river backwaters often fall prey

to kingfishers.

Fishermen often catch rudd,

which rise to their bait. Since

rudd are not usually eaten,

however, most of the fish are

thrown back.

small floating insects such as

mosquito larvae. In summer

large rudd are a major threat to

the young fish that feed on the

tiny planktonic animals swarm­

ing beneath the surface of rich

lowland lakes.

The rudd's steeply angled

mouth is ideal for snapping up

flies that fall into the water, but

it is ill suited for feeding on the

~ BREEDING & GROWTH From April to June rudd move

into shallow waters to spawn,

often congregating in large

schools around submerged

plants. The fish may be seen

rolling at the surface as the

males weave through the

schools, fertilizing the eggs.

The transparent eggs become

attached to water plants, which

helps prevent them from being

eaten by predators (including

other rudd) or being swept

away into unsuitable waters.

The eggs hatch in 8 to 15

days, depending on the water

bottom. Like all its relatives in

the carp family, the rudd lacks

teeth in its jaws. Instead, it has

bony knobs mounted on bones

on each side of its throat. It

grinds these knobs against a

hard, horny pad in the roof of

its throat to crunch up insects.

Below: Rudd thrive in warm water and often congregate at water out­lets near power stations.

temperature. The emerging lar­

vae look like tiny, transparent

fry. Each larva has a yolk sac

with nutrients that sustain it

during its first days of life. The

tiny fish then begins to feed on

microscopic floating animals.

At a year old, the young fish

DID YOU KNOW? • Rudd found in isolated

gravel pits may arrive as

eggs, stuck to the feet of

birds that fly in from lakes.

• Spawning rudd often

get mixed up with roach

and bream, and many

eggs develop into hybrids

that share the characteris­

tics of both parents.

are about three inches long

and begin eating plant food.

They soon start eating insects.

If food is abundant, they may

grow up to 18 inches long. But

since most rudd live in poor

conditions, the mature fish are

usually much smaller.

STICKLEBACK GROUP 4: FISH

... ORDER ~ Gasterosteiformes

... FAMILY ~ Gasterosteidae

... GENERA & SPECIES ~ Gasterosteus aculeatus, etc.

Sticklebacks are named for their dorsal spines, which may offer some protection from predators. In the breeding season the males

become brightly colored and care for the young.

KEY FACTS SIZE

Length: Usually 2 in. Rarelyex­

ceeds 4 in., but 15-spined stickle-

back can reach 8 in.

BREEDING

Sexual maturity: At end of first

year (3-spined stickleback).

Mating season: Spring to summer.

No. of young: Each nest of the 3-

spined stickleback yields approxi­

mately 100 young.

LIFESTYLE

Habit: Lives in loose schools except

in the breeding season, when the

male is territorial.

Diet: Aquatic invertebrates; occa­

sionally waterweeds.

Lifespan: 3-spined species lives to

3 years.

RELATED SPECIES

There are 5 species of stickleback in

5 genera.

STICKLEBACKS' NESTS

Nine-spined stickleback: The male makes a rounded nest from algae and weeds in vegetation near the riverbed or seabed. He binds the materials together with a sticky substance from his kidneys.

Female: Lays eggs, but male cares for eggs and young when they hatch.

Three-spined stickleback: The male makes a moundlike nest from weeds in a hollow on the riverbed or seabed.

•

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Range of the three-spined stickleback.

DISTRIBUTION

The five stickleback species can be found in fresh and coastal

waters throughout the Northern Hemisphere.

CONSERVATION

All sticklebacks suffer from the pollution and draining of their

habitats. Although some species are restricted in their distribu­

tion, none are seriously threatened.

'--_~-=-':' ___ Throat: Nine­spined stickle­back's throat deepens from brown to black during breeding.

~ __________ ~ __ Belly: Three-

PRINTED IN U.S.A.

spined stickle­back lures a female to the nest with his

' . bright red belly and blue eyes.

0160200641 PACKET 64

Sticklebacks are some of the most familiar fish of the ~ ~ BREEDING

Northern Hemisphere. They are able to live in fresh water Sticklebacks breed from late

as well as salt water, and some species occur in both

kinds of habitats. These adaptable fish can be found

in even the smallest ponds and ditches.

~ HABITAT Sticklebacks can be found in a wide range of watery habitats, from ditches and the edges of lakes to the sea. Only one spe­cies, the fifteen-spined stickle­back, is never found in fresh water and spends its life at sea.

The most familiar species is the three-spined stickleback. It occurs in most of the Northern Hemisphere, living in streams, rock pools, and ditches. It usu-

ally stays near the shore, but it is sometimes found at the sur­face in the open sea.

Sticklebacks often live in loose schools, except in the breeding season, when males become fiercely territorial. All sticklebacks have spines that may provide some protection from preda­tors, but they still fall prey to water shrews, otters, larger fish, and certain water birds.

March to early August, when food for the young is plentiful. Some species migrate from the sea to breeding grounds in riv­ers and streams. Those that do not migrate breed where they spend the rest of the year.

In most species, the male takes on bright coloring and becomes very territorial during breeding. He builds a nest on the bottom or among water­weeds and then entices fe­males to enter this nest.

The females lay their eggs in the nest, and the male fertilizes them. He guards the eggs and the young when they hatch, tending them for a few weeks until they are independent.

Above: 5tickleback eggs three days after fertilization .

Above right: A young stickle­back with its yolk sac.

Right: A male stickleback cares for his week-old young.

~ FOOD & FEEDING

Sticklebacks have a varied diet. They feed primarily on small aquatic animals such as insect larvae, crustaceans, small mol­lusks, and worms. They also eat young fish and fish eggs, includ­ing other sticklebacks' eggs.

Sticklebacks hunt at night, watching for the movement of prey. They need good light for hunting and probably feed only when the moon is bright.

When sticklebacks spot a potential meal, they chase it if necessary and seize it by sud­denly pushing their jaws open. The jaws are protractile (stretch­ing out away from the mouth). After the prey is sucked in, the fish grabs it with small, needle­sharp teeth.

When one stickleback finds food, others rush to join it, be­cause there may be more food in the area.

left: A three-spined male tends his nest of woven weeds.

Below: A male stimulates his mate to lay eggs in the nest.

DID YOU KNOW? • Sticklebacks are caught for uses other than food. They are made into oil and animal feed and may be used as fertilizer. • Freshwater sticklebacks are usually smooth, but many sticklebacks living in salt water have thin, bony plates on their sides. • Sticklebacks can be pests. In the Black Sea region of Europe, the three-spined stickleback eats the young of fish that are caught for human consumption. It also competes with these fish for food. • Sticklebacks that spend time in both fresh and salt water must deal with dif­ferences in water salinity. They do this by maintain­ing a certain concentration of salt in their body fluids -a function carried out by their gills and kidneys.

VIPERFISH

ORDER Stomiiformes

FAMILY Chauliodontidae

GENUS Chauliodus

Viperfish live more than a thousand feet below the surface of the ocean. These deadly predators are well adapted for hunting

other fish in the dark waters of the ocean depths.

KEY FACTS

SIZES

Length: Up to 1 ft.

BREEDING

The breeding habits of viperfish are

not known. They are thought to

produce large quantities of eggs

that hatch into larvae before be­

coming adults.

LlFESTLYE

Habit: Solitary, slow-swimming

predators, usually found at depths

of 1,300-2,600 ft.

Range of viperfish. Diet: Various deep-water fish,

some of which may be as large

as viperfish. DISTRIBUTION

RELATED SPECIES

The family Chauliodontidae con­

tains 6 species of viperfish in the

single genus Chauliodus. Sloane's

viperfish, C. s/oani, is the largest

viperfish . C. danae, C. minimus, and

C. pammelas are other members of

the same family.

Viperfish have been found in all temperate and tropical oceans.

Sloane's viperfish prefers the richer waters away from the rela­

tively barren midocean.

HOW VIPERFISH HUNT

CONSERVATION

Because they live in remote ocean depths and have no com­

mercial value, viperfish are probably safe from the influence

of humans.

Left: At rest, the jaws of a viperfish are usually closed. But they can be opened wide to swal­low large prey.

Left: A viper­fish has a light at the tip of its mobile dorsal fin ray, which it uses to at­tract the atten­tion of its fish prey.

Fish are scarce in the ocean depths, but viperfish can hunt and catch prey as large as themselves.

Below: This viperfish has caught a large fish and forced it halfway into its mouth. It holds the fish with the teeth in its palate to prevent es­cape. The jaws are raised upward, hinged on the front part of the backbone.

The viperfish expands its throat and

swallows the fish quickly.

During this difficult process, the viper­fish 's gills are pulled downward and

backward and are exposed . Blood circulation and breathing are impeded.

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A viperfish is a threatening-looking luminous creature

that has an expandable stomach/ huge jaws/ and

long/ sharp teeth. This typical predator of the ocean

depths is capable of trapping and engulfing almost

any animal it encounters in the deep/ dark seas. By

unhinging its jaws and expanding its throat/ a viperfish

can even swallow and kill prey as large as itself.

~HABITAT Light cannot penetrate ocean

waters below a certain depth. The different colors of the spec­

trum that make up white sun­light are filtered out at different

rates as they pass through the dense salt water. Red light waves are absorbed first, fol­

lowed by the oranges, yellows,

and greens until, at about 650 feet below the surface, only the blue light remains.

The blue twilight gets dimmer with increasing depth and fades

completely at about 3,000 feet in the clearest water. Below this

depth, all is inky darkness. Viperfish inhabit the blue twi-

light area. Fish are very scarce

at these depths because there is little for them to feed on. All

life ultimately depends on the plankton (tiny plants and ani- '

mals) that drift down from the higher depths.

At night the plankton move

upward to feed on organisms that live on the water surface. They are followed by small

deep-water fish, such as bristle­mouths, that prey on them.

These fish return to the ocean depths at dawn, their stomachs

full of plankton, and are then eaten in turn by larger preda­tors like viperfish.

DID YOU KNOW? • A viperfish's eyes are be­lieved to be up to 30 times more sensitive to dim light

than a human's eyes.

• More than 98 percent of the energy that is fed to a viperfish's luminous organs

is converted to light. A do­mestic light blub converts

~ BREEDING Although divers have observed viperfish from deep-water sub­mersible crafts, the breeding

behavior and other habits of these fish remain a mystery. It

is likely that viperfish produce large quantities of eggs that hatch into tiny larvae before

developing into adults.

Left: A viperfish can use the "bait" on the end of its dorsal fin ray to lure fish.

Right: A viperfish's body is covered with a thick, watery layer enclosed by a thin skin.

only three percent of the electrical energy into light.

• If touched, a viperfish's body is lit by pulses of light.

• A viperfish's light organs are modified glands. Sloane's

viperfish has over 1,500

compound light organs on its body.

rr~~ . ~ SPECIAL ADAPTATIONS Most fish that live in the dimly

lit deep ocean waters have

luminous organs. A viperfish has lights around its eyes, a bright fin ray lure, and rows of

photophores (glowing organs) along its flanks and belly that

give off a subdued blue glow.

~ FOOD & HUNTING Viperfish hunt mainly by sight,

relying on their big eyes to pick up the movements of fish

that swim through the deep­sea gloom. Each eye has a

light-producing organ directly beneath it that shines upward

into the eye, improving its sen­sitivity to light. Other light or­

gans above and in front of the eyes act as spotlights, shining

on the prey as the viperfish moves in for the kill.

Active hunting is one way

to find prey. But in the ocean

Left: Viperfish sometimes catch large prey but more often kill small hatchetfish.

This light matches the glim­

mer of blue light that filters down from the surface, so a viperfish does not cast a shad­

ow on the water below. This "camouflage" conceals it from

larger predators approaching

from the depths below.

depths, where food is scarce, a viperfish makes use of anoth­

er method as well. The second ray of its dorsal fin is very long,

with a bright lure on the tip. A viperfish rests in the water

with the lure dangling in front of its mouth to attract poten­

tial victims. When a fish is caught in a

viperfish's mouth, there is no escape. The stiletto-shaped

teeth of the upper jaw are designed to stab prey and hold

it fast. A viperfish can open its mouth wide and unhinge the lower jaw from the body to

accommodate large prey.

TETRA

... CLASS ~ Osteichthyes

ORDER Charociformes

FAMILY Charocidae

GROUP 4: FISH

Tetras are small freshwater fish that feed in large schools, mainly in the slow-flowing, silted rivers of Central and South America.

Some of these fish glow with iridescent color.

KEY FACTS

SIZE

Length: Mostly 1 ~-2~ in ., but the

glass tetra grows to 8 in.

BREEDING

Sexual maturity: 1-2 years.

Eggs: 100-300, laid in batches.

Hatching time: 1 -5 days.

LIFESTYLE

Habit: Found in schools in midwater.

Diet: Varied. Eat small animals, in­

sects, carrion, and plant matter.

Lifespan: 3-4 years.

RELATED SPECIES

The 841 fish species in the family

Charocidae are found in Central and

South America and Africa. Relatives

include the flying hatchetfish of the

family Gasteropelecidae and the pi­

ranha, Serrosalmus nattereri. Also

related is the family Lebiasinidae,

which includes the tube-mouth

pencil fish.

Range of tetras.

DISTRIBUTION

Most tetra species are found in the rivers of Central and South

America, but a few species live in Africa.

CONSERVATION

Although tetras are popular aquarium fish, captive breeding

fulfills most of the demand and keeps collection from the wild

to a minimum in most cases. Tetras that are less easy to breed

in captivity are at greater risk.

BREEDING HABITS OF THE SPLASHING TETRA ~ ,

Leaps up to lay her eggs on a low leaf, where they are safe from predators. The sticky eggs adhere to the leaf by surface tension.

3. Male: Re­mains near the eggs, continually leaping up to splash them with water and keep them moist until they hatch.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

2. Male: Leaps up to shed sperm on the eggs, fertilizing them. The male may fertilize up to 200 eggs in this way.

4. Young: Hatch after 3 days and drop i.nto the wa­ter. The male's parental duties are then over.

PRINTED IN U.S.A. 0160200561 PACKET 56

Tetras are small, tropical relatives of the carp that

were once classified in the genus Tetragonopterus.

Although scientists no longer use this genus name,

these freshwater fish are still popularly referred to

by an abbreviated version of this term-tetra.

Because of their vivid colors, tetras are popular

in aquariums, and they breed well in captivity.

~COlORATION Many tetras are so vividly col-ored that it is hard to imagine how they survive in the wild.

The cardinal tetra, for example,

has bright red flanks topped by a broad streak of electric blue

that extends from head to tail. The diamond tetra sparkles with iridescent green and gold,

while the glowlight tetra ap­pears to have a red-hot rod running down its translucent

green body. These dramatic colors have

a function. In the tropical riv­ers and lakes where most tetras

are found, the waters may be

colored green by microscopic

plants, milky white by clay par­ticles, or deep brown by the peat formed from decompos­ing forest leaves. Visibility is fre­

quently poor, and the tetras' bright colors act as navigation lights, enabling individuals to

stay in contact with each other. Rather than exposing the fish

to danger, the glittering colors may help protect them by bringing them together and providing safety in numbers.

Right: The neon tetra gets its name from the luminous stripes that line its sides.

~ FOOD &: FEEDING Tetras live in loose schools among plants in the middle layer of still or slow-flowing water. Although some tetra

species eat only plant matter, most tetras are omnivorous

opportunists-eating anything small and edible that does not devour it first.

In the tropical rivers where

they live, tetras find a rich sup­ply of food . In addition to plant matter, they eat insect larvae and worms from the river bot-

Left: In the wild the young black tetra is social, but it becomes more solitary with age.

tom and insects from the sur­face. They even eat animals that are caught in rising floodwaters.

Tetras' readiness to consume

almost anything can produce problems with captive fish. Many species kept in captivity even devour their own eggs and young . It is not known

whether this happens in the wild, but the tendency is prob­ably exaggerated in an aquari­

um, where there is often no other food available.

Right: Because tetras have a very wide food base, they rarely go hungry.

Left: The Congo tetra is one of the few species found in Africa. Tetras are of great interest to biol­ogists because they adapt readily to new conditions and habitats.

DID YOU KNOW? • The cave characin is a com­pletely blind tetra that lives in underground streams in Mexico. It uses its senses of

smell and touch to find its way around.

• Wild tetras are hardly ever caught for the pet trade be­

cause the popular species breed well in captivity.

~ BREEDING Some male tetras become very animated during the breeding season. A male black tetra, for

example, circles a female with his fins spread out. He zigzags in front and drives her in and

out of vegetation. Most female tetras scatter their

eggs at random in batches of a

dozen. The transparent, slightly sticky eggs cling to plants. After laying several batches of eggs, the female abandons them. The

male smothers the eggs with sperm to fertilize them, and they hatch in two or three days. The hatchlings feed on micro-

• The brilliant colors of many tetras are "interference colors" caused by refraction of light. When the fish moves out of

the light, the colors blink off, so the fish blends into its back­

ground. The bright reds of the cardinal and neon tetras, on the other hand, are caused

by pigment.

scopic water plants and animals. The splashing tetra has more

unusual breeding habits. By

laying its eggs on plant leaves hanging over the water, this species may reduce the risk of

its eggs being eaten before they hatch. The female leaps out of the water and clings briefly to the leaf while shed­

ding her eggs. The male fol­lows suit to fertilize them. The

male then sprays the eggs with water in order to keep them damp. When the eggs hatch, the young fish fall into the wa­ter and swim away.

~ CARD 37

REEF SHARK \(~ ___________________________________ G_R_O_U_P_4_:_F_IS_H __ ~

CLASS ~ Chondrichthyes ORDER Pleurotremata

FAMILY Carcharhinidae

Moving stealthily through tropical coral reefs, reef sharks are highly efficient killers. These creatures have little to fear except larger

predators of their own kind and the ever-present threat of humans.

KEY FACTS

SIZE

Length: Varies, from 5 ft. in the

black-tip reef shark to 16 ft. in the

tiger shark.

LIFESTYLE

Habit: Active predators by day

and night.

Diet: Mainly fish, crustaceans,

cuttlefish, and octopuses.

BREEDING

Sexual maturity: Approximately 2

years, depending on growth rate

and size.

Breeding season: Summer.

Gestation: 8-12 months, depend­

ing on species.

No. of young: About 14; fully

formed when born.

RELATED SPECIES

There are 17 genera and approx­

imately 60 species in the family

Carcharhinidae.

Range of reef sharks.

DISTRIBUTION

Reef sharks are found mainly on coral reefs in the tropics, but

some penetrate cooler, temperate waters in summer.

CONSERVATION

Sharks worldwide are threatened by sport fishing. They are also

threatened by the practice of tinning, in which the fins are cut

off for use as food, and the mutilated fish are then thrown back

into the water to die.

FEATURES OF THE BLACK-TIP REEF SHARK

Female

Dorsal fin : Has a black tip, which may be used as a social recog nition signal.

Claspers: Found in male only. Two external sexual organs, one of which is inserted into the female during mating.

Scars: On fins and rear of female's body. Caused by male biting female to grip her during mating.

©MCMXCVI IMP BV/IMP INC. WILDLIFE FACT FILETM PRINTED IN U.S.A us P 6001 12 073 PACKET 73

Reef sharks belong to the family Carcharhinidae, which

contains approximately 60 species. Most of these species

inhabit coral reefs in tropical waters. They are able to

coexist by exploiting different types of prey on separate

parts of the coral reef. Reef sharks vary widely, from the

small, fish-eating black-tip shark to the huge, fearsome

tiger shark-which has been known to kill humans.

~ HABITAT Reef sharks are usually found on

coral reefs and in nearby tropical

waters. A typical site is a shallow,

sandy lagoon with scattered cor­

al formations, bounded by an

area of built-up coral known as

a "reef flat." On the seaward

side, the reef flat falls away steep­

ly into deep waters, which are

linked to the lagoon by chan­

nels that form the reef sharks'

access routes.

Gray reef sharks generally fre­

quent the deep waters of the

outer reef slope, but they often

congregate in the channels and

use them to enter the lagoon.

The small black-tip reef shark

can swim in shallower water. It

hunts over the reef flat at high

tide, with its dorsal fin cutting

the surface. The slightly bigger

white-tip shark prefers deep gul­

lies and caves, while the large

silver-tip shark usually stays on

the outer reef slope. Largest of

all is the tiger shark, which slips

into the channels from the out­

er fringes to pick off large fish­

including other sharks.

~ FOOD & HUNTING Reef sharks are opportunistic

feeders that eat just about any­

thing, from shellfish to sea lions.

The black-tip reef shark feeds

on crabs, lobsters, cuttlefish,

and small reef fish. It hunts pri­

marily at night in an area that

is familiar, ambushing its prey

among coral heads in the reef

shallows. Although the white­

tip reef shark also hunts at night

for similar prey, it forages in dif­

ferent waters, taking bottom­

dwelling fish and octopuses from

the reef's caves and crevices.

The larger, stronger gray reef

Left: Most reef sharks inhabit trop­ical waters, but some species enter temperate waters.

DID YOU KNOW? • Reef sharks are highly devel-

oped at birth. One infant bit a

scientist as he removed it from

the dying mother's womb.

• Although reef sharks are dangerous, they can be sur­

prisingly tame. Several have

been trained to take fish from

divers without biting them.

• Although reef sharks are re-

shark hunts for bigger prey in

deep water by night and day.

The silver-tip hunts similar prey

at similar depths, which may

partly explain why the gray reef

shark is so aggressively territori­

al. The gray reef shark warns

intruders by twisting its body,

raising its snout, and dropping

its pectoral fins. It finally attacks

with slashing bites that are not

part of its normal feeding meth­

od. It can even drive off the 16-

foot tiger shark, which can kill a

gray reef shark and then swal­

low it whole.

Right: Reef sharks often feed in groups and may participate in "feeding frenzies. "

garded as voracious feeders,

they can actually go for days

without eating. The sharks

convert energy so efficiently

that they can get by on rela­

tively little food.

• Reef sharks locate prey by detecting tiny electrical signals

that are generated by their vic­

tim's nervous system.

Reef sharks breed in summer.

After following a female's scent

trail through water, the male

grips her body or fin with his

teeth, usually wounding her

despite her thick skin. He then

inserts one of two elongated

claspers (sexual organs) into

her cloaca (genital opening).

The clasper acts as a guide for

the sperm, which is passed into

a special sac within the female

Left: Reef sharks give birth to live young that are perfect miniatures of their parents.

Left: Small fish called remoras sometimes "hitch a ride" on reef sharks. The remoras use suckerlike disks on their heads to attach themselves to the reef sharks.

and stored for several months

before fertilizing her eggs the

following spring .

Like infant mammals, the

unborn sharks are connected

to the mother's bloodstream

by an umbilical cord and pla­

centa. This enables them to

absorb nutrients during the 8-

to 12-month gestation period .

Unlike other fish, whose off­

spring are born from eggs that

hatch in water, the female shark

gives birth to relatively few well­

formed, live young.

BUTTERFLY FISH

ORDER Perciformes

FAMILY Chaetodontidae

GROUP 4: FISH GENERA Chaetodon, Forcipiger, etc.

Butterfly fish are brightly colored relatives of angelfish. They live in shallow tropical seas, where they feed on the small

animals that live in or near coral reefs.

KEY FACTS ______________________________________________________ -J

SIZE

Length: 2-8 in., depending on

the species.

BREEDING

Eggs: Laid in large batches. Young

are cared for by both parents until

independent.

LIFESTYLE

Habit: Live in reefs . Swim in pairs

or small groups. Active mostly dur­

ing the day.

Diet: Mainly coral polyps. Also

small marine creatures such as

worms, sea slugs, and bottom­

dwelling shrimp.

Lifespan: Several years in captivity;

unknown in the wild.

RELATED SPECIES

Butterfly fish are so closely related

to angelfish that-until recently­

they were classed in the same fam­

ily. An angelfish has a spine on its

gill cover, which is lacking in a but­

terfly fish .

~.

• Range of butterfly fish .

DISTRIBUTION

Found in coral reefs bordering tropical seas and oceans, includ­

ing parts of the Pacific, Indian, and Atlantic oceans; the Carib­

bean; the Arabian Sea; and the Bay of Bengal.

CONSERVATION

Like all reef animals, butterfly fish are threatened by pollution

and damage to coral reefs. Local populations of some species

may be affected by overcollection for the aquarium trade.

FEATURES OF BUTTERFLY FISH

Eyespot: A common marking in many species. It mimics the fish 's eye and tricks a predator into attacking the tail fin instead of the vulnerable head .

Mouth: Varies depending on the species. Some have long, pipelike jaws for plucking food from coral crevices. Others have shorter, beak­like jaws for grazing on coral polyps.

©MCMXCIV IMP BV/IMP INC WILDLIFE FACT FILETM

Spines: Very sharp, lining the dorsal fin . They may deter a predator from eating the fish .

long-nosed butterfly fish,

Forcipiger f/avissimus

PRINTED IN U.S.A.

Color and pattern: Each species, and possibly each individual, has its own special markings. The stripes and spots conceal the fish 's body outline from predators and help it recognize other butterfly fish .

US P 6001 12067 PACKET 67

There are more than a hundred species of

butterfly fish in the world's warm oceans. Famous

for their vibrant colors, they are frequently displayed

in aquariums. With their deep, narrow bodies, these

fish look like butterflies at rest with closed wings. As

they dart from one coral branch to another, they

resemble butterflies flitting among flowers.

~ HABITAT Butterfly fish live in coral reefs

in the sunlit, shallow seas near

the equator. The tropical reefs

offer shelter to sea anemones,

worms, sponges, shellfish, and

starfish. The surrounding wa­

ters are thick with plant and

animal plankton, providing

food for many species of fish.

These fish are in turn eaten by

Right: A but­terfly fish is pro­tected from predators by the pin-sharp spines on its dorsal fin and by the speed with which it darts outof danger.

larger predators such as bass

and groupers.

The vividness of butterfly fish

fits into the brilliantly colored

coral environment. These fish

have striking body patterns

that help break up their out­

lines and at the same time

serve as identification "flags"

to their mates.

~ BREEDING In preparation for spawning, a

pair of butterfly fish cleans the

debris from a flat rock. The fe­

male then lays her eggs on the

cleaned rock, and the male im­

mediately swims over them,

producing clouds of sperm to

fertilize the eggs. Both fish stay with the eggs

until they hatch in about four

to eight days. After hatching,

Left: The saddled butterfly fish inhabits the coastal reefs of Aus­tralia and Central America.

DID YOU KNOW? • A butterfly fish known as the wimplefish is a "cleaner,"

nibbling parasites and dead

skin from other fish. Even a

dangerous predator stays still

to let this fish clean its body.

• The four-eyed butterfly fish fools predators with the eye­

like spots above its tail, which

make it hard to tell front from

the fry (young) sink to the sea­

bed, where both parents pro­

tect them until they can swim

and feed themselves.

The long, slim fry look very

different from their parents.

Each finds a shelter under a

rock or plant and protects the

surrounding area. In three or

four months, it develops into

the adult form.

Right: In many butterfly fish spe­cies, an eyespot near the tail helps confuse predators.

back. To increase the confu­

sion, the fish first swims slow­

ly backward and then darts

forward at high speed.

• Some species, such as the ornate butterfly fish, can ad­

just their body coloration at

night. This ability may allow a

breeding pair to identify each

other 24 hours a day. ----1

~ FOOD &: FEEDING Butterfly fish graze on coral

polyps. They also eat small sea

creatures in the reef's crevices.

Some species, such as the sun­

burst butterfly fish, have short

jaws and flat, grinding teeth to

bite through the coral skeleton

and devour the coral polyps. In

contrast, the forceps fish has

long, beaklike jaws and very

sharp teeth. It bites off single

polyps or plucks small animals

from their hiding places. Most adults feed alone or in

small groups. Each group has its

own feeding ground. To warn

other fish away, males flash their

colorful fins. Only the forceps

fish fights intruders, raking them

with its sharp dorsal spine.

". BUTTERFLY FISH ""lIIIIII &MAN

Butterfly fish are so popular in

aquariums that every known

species has a common name,

usually describing its appear­

ance. The sunburst, for exam­

ple, is colored orangish gold,

while the yellow long-nose has

very long jaws.

It is possible to nurture living

coral polyps in an aquarium to

provide captive butterfly fish

with their natural food. But

there is disagreement about

whether people should take

butterfly fish from their natural

habitat, where they may be vi­tal to the coral reef food chain.

Left: 5addle markings and eye stripes camouflage this butterfly fish by breaking up its outline.

EUROPEAN MINNOW

ORDER Cypriniformes

FAMILY Cyprinidae

GENUS fit: SPECIES Phoxinus phoxinus

The European minnow is a tiny relative of the carp. This adaptable little fish can live in almost any fresh, clean water,

and it eats almost everything it can catch.

KEY· FACTS

SIZE Length: 3-4 in. Occasionally grows up to 5~ in. The female is bigger than the male.

BREEDING Sexual maturity: 1-2 years. Spawning season: April to July. No. of eggs: Up to 1,000. Hatching: 5-1 0 days.

LIFESTYLE Habit: Sociable. Forms schools in shallow, clear water. Diet: Aquatic invertebrates such as worms, insect larvae, and crusta­ceans. Also flying insects and some plant matter.

RELATED SPECIES There are 2 closely related species in northern Europe: the swamp minnow and the Poznan minnow. Other members of the large family Cyprinidae include the goldfish, Carassius auratus.

Range of the European minnow. --------DISTRIBUTION The European minnow is found in most of Europe, and its range extends across northern Asia to the Bering Sea. It is not, however, found in Arctic regions.

CONSERVATION Although still common in much of its range, the European minnow suffers badly from the effects of pollution. It has dis­appeared from many lowland rivers.

FEATURES OF THE EUROPEAN MINNOW

Coloration: Variable. Back and sides are often deep olive green with a metallic bronze sheen on the sides blending into a pale yellow or whitish belly.

Male: Becomes flushed with red during the spawning sea­son and de­velops white bumps on his head.

Female: Characterized by a deep, fat belly full of eggs during the spawning season .

Senses: The minnow picks up vibrations through lines

that run the length of its

body.

Eggs: Small, pale yellow, and covered with mucus. The female lays up to 1,000 eggs in small clumps on the

riverbed, where they stick to gravel , stones, or aquatic plants. The eggs are fertilized by the male, and they

hatch after about a week.

c; o <0 a.. (J) ::J

The European minnow is an important link in the food

chain of lakes and rivers. This small fish consumes huge

quantities of a wide range of aquatic insects and other

small creatures. In turn it is preyed upon by a variety of

larger fish as well as birds. Occasionally the European

minnow is even eaten by swamp spiders as well as by

carnivorous insects such as the great diving beetle.

~ HABITS The European minnow is com­

mon in clean, fresh waters in

much of Europe and northern

Asia. It is most numerous in the

fast-flowing upper levels of riv­

ers. It also lives in lakes or ponds

if the water is not too muddy and

there is plenty to eat.

The European minnow is an

easy catch for various predatory

fish and fish-eating birds. Occa­

sionally it is also preyed upon by

carnivorous insects. Its main de­

fenses are its agility and instinc­

tive avoidance of the open-water

hunting areas of larger fish . Stay­

ing in shallower water, it takes

cover in plants near the banks.

In summer European min­

nows gather in schools of up to

a hundred to feed near the sur­

face. They often swim with oth­

er small fish, such as young dace,

bleak, and roach. Schools offer

safety in numbers, but in winter

they break up and each minnow

moves closer to the riverbed.

Relying on its dark, mottled col­

oring for camouflage, the min­

now swims close to the bottom.

It hides under stones when the

river swells with heavy rain and

powerful currents threaten to

sweep it away.

~ FOOD &: FEEDING Like most fish that live in a vari­

ety of waters, the European min­

now is adaptable, eating almost

anything that it finds. Although

it may nibble on water plants

and eat algae growing on stones

or plant stems, it prefers to feed

on small animals.

The minnow preys mainly on

freshwater shrimps, worms, and

the aquatic larvae of insects like

the caddis fly, mayfly, and mos­

quito. But it attacks other small

creatures it comes across, even

left: The European minnow favors clean, oxygen-rich waters, which provide plenty of food.

DID YOU KNOW? • A European minnow alters

its coloring according to its

mood. When alarmed, it may

become almost colorless.

• In medieval Europe, min­

nows were caught for food

and were so prized that they

were served at state banquets.

In some parts of Europe they

are still caught for food.

leaping from the water to seize

an insect from the air.

Like other members of the

carp family, the European min­

now has no teeth. Instead, it has

special nodules on the bones at

the back of its gill chamber. The

minnow uses them to grind its

food against a horny pad . Each

species within the family has a

different arrangement of these

"teeth." They are often the only

reliable way to distinguish be­

tween similar carp species.

Right: The European minnow has a flexible pair of jaws that it thrusts forward when feeding.

• After an absence of many

years, minnows returned to

London's Thames River in the

1970s, showing that the water

had become cleaner.

• The European minnow is a

favorite prey of the European

kingfisher. It is exposed to at­

tack from above because it

feeds near the surface.

I, ,,~j NATUREWATCH The European minnow can

be caught with a net in streams

and ponds. Its mottled dark

olive back makes it easy to

recognize, but there are some

color variations. A minnow

living in cloudy water is paler

and less strongly patterned

~ BREEDING The European minnow is usually

a drab color with a dark green,

blotchy back and a silvery belly.

But in the breeding season the

male's belly becomes flushed

with red and he develops a rash

of hard, conical white bumps

on his head. At the same time

the female's belly swells with

eggs. The sexes mingle in a

large school before pairing and

spawning at the river bottom.

As the small mucus-covered

eggs are laid, they stick to the

left: An injured minnow releases chemicals that warn the rest of the school to scatter.

than one in a clear stream.

In summer minnows can

often be seen in large schools

near the surface in shallow

river waters . Because these

fish live only in clean water,

their presence indicates that

the river is not polluted .

rocks in clumps. The male fertil­

izes them, and they hatch in five

to ten days. The warmer the wa­

ter, the faster the eggs develop.

Each newly hatched fish stays

among the stones at first. It lives

off the contents of the yolk sac

attached to its stomach. When

that is gone, the minnow has to

find its own food . It eats tiny

microorganisms that float in the

water until it is big enough to

tackle insects and worms.

If conditions are right, the min­

now grows quickly enough to

breed within a year. But many

take two years to mature.

BLENNY ",CARD 40

GROUP 4: FISH " ~ " ~ ORDER Perciformes

FAMILY Blenniidae

GENERA Various

There are hundreds of species of blennies. All of these species are found in shallow coastal waters in the temperate and tropical parts of the Atlantic, Pacific, and Indian oceans.

KEY FACTS

SIZE

Length: Varies. Can measure up

to 12 in.

BREEDING

Sexual maturity: 1 year.

Spawning: Varies depending on

the species.

No. of eggs: Varies depending on

the maturity of the fish.

Hatching period: Varies depending

on the species.

~ LIFESTYLE

Habit: Territorial. Individual guards

home range.

Diet: Barnacles, small crustaceans,

some algae and seaweed.

Lifespan: Up to 4 years.

RELATED SPECIES

There are more than 275 species in

the family Blenniidae.

FEATURES OF BlENNIES

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Range of blennies.

DISTRIBUTION

Blennies are found in shallow water in tropical and temperate

parts of the Atlantic, Pacific, and Indian oceans.

CONSERVATION

Blennies are not currently in danger. But because they live in

coastal waters, they are more susceptible to pollution than

open-sea fish.

Eggs: Female lays batch in debris or hole. Male fans eggs with fins to oxy­genate them.

PRINTED IN U.S.A.

Coloration: Many blennies change color for various reasons. De­fense, aggression, submission, breeding, and spawning can cause color changes. Blennies also use color changes for camouflage.

0160200591 PACKET 59

Blennies can be found in rock pools

around coastlines. They have many enemies

that prey on them when the rock pools are shallow

and exposed at low tide. As a result, these small fish

have developed a variety of tactics for defense.

~ HABITAT Because they live in shallow wa­ter, blennies must cope with the tides and extremes of tempera­ture. When exposed to the sun, the water in a rock pool can be­come very hot. In cold waters, the temperature can drop to freezing. Rain trapped in rock pools can change the salt con­tent of the water, and blennies must make biological changes to counteract the effects.

Blennies have many enemies and several ways of coping with them. Some species, such as the shanny, change color in order to camouflage themselves against their background. Other species hide in crevices or under rocks. Still other species, such as the tompot bien ny, hide in kelp and seaweed.

~ BREEDING Most North Atlantic blennies spawn between April and Au­gust. The male fertilizes the eggs, which are rarely larger than the head of a pin. The eggs are usually laid under stones and rocks but may sometimes be hidden in discarded receptacles such as bottles or cans.

After laying the eggs, the fe­male abandons them. The male guards the eggs and fans them with his pectoral fins to make sure they get enough oxygen. The young fish, called f'Yt are very vulnerable, and many are eaten by predators.

The eel pout, which is related to blennies, gives birth to be­tween 20 and 300 live young, depending on the female's size. The eggs hatch inside the fe-

~ FOOD &: FEEDING The majority of blennies are territorial. They feed within a certain area, which they guard against other blennies. Some blenny species have tiny teeth and nibble the limbs of barna­cles. Other species have pow-

left: The viviparous blenny gives birth to already hatched young.

Right: Many species of blenny can "haul out" on the rocks.

Far right: The jewel-like dia­mond blenny lurks in the wav­ing tentacles of an anemone.

male's body after about three weeks, but it is four months be­fore the young are born. As a result of this delay, the newborn fry are well developed and have a better chance of surviving.

erful, curved teeth and attack fish larger than themselves.

Blennies also eat tiny crabs, bristleworms, and other small shellfish, as well as seaweed. In aquariums, they are fed worms and small pieces of meat.

Above: The male sabre-toothed blenny stays with the developing eggs and guards them.

Above right: Yarrell's blenny is one of many species that have the branched tentacles shown here.

DID YOU KNOW? • Some blennies can leave the water to rest on rocks or escape from predators. • Blennies dig shelters under rocks by wriggling their bod­ies in the sand.

[- ,-] NATUREWATCH Blennies move very quickly. If you move a stone in a rock pool, you may see a blenny dart out to find another hid­ing place. Blennies are very wary of overhead shadows, and they will quickly notice

• A blenny's eyes move inde­pendently of each other, so it can see predators both in and above the water. • Blennies of the genus Runu-10 may bite swimmers.

your presence. Some blennies are bold enough to venture into open water.

If you can catch a blenny in a glass jar, you will be able to study it in detail. But be sure to return the fish to its pool.