Animal Class: Fish

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Spotted Garden Eel

Heteroconger hassi

A swaying colony of spotted garden eels could easily be mistaken for plants.  These animals extend their bodies out of individual burrows to find tiny zooplankton to eat, but if they spot danger, the eels can pull their bodies completely into their burrows to hide.

Classification

CLASS:Actinopterygii
ORDER:Aulopiformes
FAMILY:Congridae
GENUS:Heteroconger
SPECIES:hassi

Habitat & Range

They live on the sandy flats that border coral reefs at depths of 23’ – 150’ (7–45m). They can also be found in areas dense with seagrass. They dig a burrow into the sandy sea bottom using their pointed tail. When the burrow is deep enough they use their dorsal fin to push the sand out of the burrow. Slime that they secrete from their skin cements the burrow walls so that the burrow will not collapse.

Spotted garden eels live in the warm parts of the Pacific Ocean and the Red Sea.

Location

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Adaptations

  • It’s pointed tail helps dig a burrow.
  • The dorsal fin is used to push sand out of the burrow.
  • When threatened they will retreat into their burrow.
  • Good eyesight allows them to spot food and predators.
  • For spotted garden eels living in areas dense with seagrass the seagrass acts as camouflage allowing them to hide in plain sight.

Physical Description

  • They resemble a worm.
  • They grow up to 16” (40cm) long
  • Their body diameter is .5” (1.3cm).
  • Adults have a white body covered in small black spots with three large black patches on their body.
  • Juveniles are entirely black.
  • They have large yellow eyes.
  • They have an upturned mouth.
  • They are sexually dimorphic, meaning males and females look different. The male is much larger than the female and it’s jaw sticks out further.

Diet

What Does It Eat?

In the wild:
They eat tiny planktonic animals that float by them in the water current.

At the zoo:
They eat flake food and hatch brine shrimp.

Social Organization

Each spotted garden eel lives in their own burrow in a colony of hundreds of eels.

Life Cycle

Spotted garden eels may leave their original burrow to move closer to mates. While mating garden eels entwine their upper halves together while their tails remain in their individual burrows. They are pelagic spawners which means the female releases fertilized eggs into the water. The eggs float until they hatch. Once the juvenile garden eels are large enough they swim down and make their own burrows.

Lionfish

Pterois volitans

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The lionfish is immediately identifiable by its brightly striped body and its long, fanlike pectoral fins. The distinctive appearance is a warning to potential predators that the lionfish’s grooved spines are equipped with venom which can cripple a predator and even kill a human. The venom of the lionfish is a defensive adaptation and is not used to catch prey.

Classification

CLASS:Osteichthyes
ORDER:Scorpaeniformes
FAMILY:Scorpaenidae
GENUS:Pterois
SPECIES:volitans

Habitat & Range

This species of fish is found in the shallow waters around coral reefs, caves or rocky areas.

Lionfish inhabit warm regions from the Red Sea across the Indian Ocean to Australia and the Pacific.

Location

north america globe

Lionfish
Lionfish
Lionfish
lionfish
Lionfish
Lionfish
Lionfish
lionfish

Adaptations

  • Nocturnal Ambush
  • Lionfish are nocturnal predators, actively feeding at night. These ambush feeders lay motionless on the bottom or underneath large overhangs of coral until prey ventures near. Then they dart forward and snap up the prey with a quick strike. Lionfish will eat any animal smaller than the size of their mouth.
  • Warning – Stay Away!
  • The lionfish is immediately identifiable by its brightly striped body and its long, fanlike pectoral fins. The distinctive appearance is a warning to potential predators that the lionfish’s grooved spines are equipped with venom which can cripple a predator and even kill a human. The venom of the lionfish is a defensive adaptation and is not used to catch prey.

Physical Description

  • Lionfish are 11.8-15 inches (30-38 cm) long.
  • They weigh about two and a half pounds (1.2 kg).
  • These fish are cryptically colored with complex patterns of red, black, brown and white spots, lines and swirls.
  • Their fanlike dorsal, pectoral and anal fins are stout and sharp.
  • Their grooved spines are equipped with venom used for defense.
  • They have heavy bodies that are laterally compressed.

Diet

What Does It Eat?

In the wild:
Fish, crabs, shrimp and occasionally plankton.

At the zoo:
Shrimp.

What Eats It?
Larger fish prey on the lionfish.

Lionfish

Social Organization

Lionfish are solitary except during breeding.

Life Cycle

Male lionfish will mate with several females. After the fish spawn, they rise to the top of the water column and release gelatinous balls of eggs each containing about 2,000 fertilized eggs. The egg balls dissolve after about 24 hours, releasing the individual eggs which hatch in about 36 hours. Even though thousands of eggs hatch, very few young fry will survive to maturity. The young fry immediately begin feeding on the available plankton or newly hatched brine shrimp. The young are almost transparent. They develop the beautiful colors and patterns of the adult lionfish as they mature. Their lifespan in the wild is unknown but they live approximately ten years in captivity.

Queen Angelfish

Holacanthus ciliaris

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Angelfish are among the most beautiful fish found in the coral reefs with brilliant colors and bold patterns. Their iridescent blue bodies and yellow tails stand out but in the colorful world of coral reefs, they actually blend in well and are able to hide from potential predators.

Classification

CLASS:Osteichthyes
ORDER:Perciformes
FAMILY:Pomacanthidae
GENUS:Holacanthus
SPECIES:ciliaris

Habitat & Range

This species of angelfish lives on mature coral reef systems.

Queen angelfish are found in the Western Atlantic Ocean from Bermuda to Brazil and the Caribbean.

Location

north america globe

Queen angelfish
Queen angelfish

Adaptations

  • Scales and Gills
  • Like all bony fish, queen angelfish have a strong internal skeleton that supports their flexible fins enabling the fish to control movement with precision. They have a gas-filled swim bladder that allows them to adjust their buoyancy. They can pump water over their gills and do not need to move forward to breathe. Their scaly skin is covered with a thin layer of mucus that protects the fish from bacteria and parasites and also makes them slippery, which helps them slide through the water.
  • Feel the Vibrations
  • Fish have a series of nerves called the lateral line extending the length of the body. These nerves are sensitive to the vibrations caused by the motion of a potential predator or food source swimming nearby.
  • Bright Colors
  • Angelfish are among the most beautiful fish found in the coral reefs with brilliant colors and bold patterns. Their iridescent blue bodies and yellow tails stand out but in the colorful world of coral reefs, they actually blend in well and are able to hide from potential predators.

Physical Description

  • Queen angelfish are up to 18 inches (45 cm) long.
  • They weigh up to three and a half pounds (1.6 kg).
  • These colorful fish have electric blue bodies, blazing yellow tails with light purple and orange highlights.
  • The body is flattened from side to side and they have a small beak-like mouth with comb-like teeth.
  • They have a speckled, blue-ringed black spot on their head that resembles a crown.
  • They have upper and lower fins that are drawn out into long trailing filaments.
  • They may have false eyespots.

Diet

What Does It Eat?

In the wild:
Sponges, algae, tunicates, anemones, coral and loose fragments of organic matter.

At the zoo:
Brine shrimp, mysis shrimp, flake food, chopped fish and vegetables.

What Eats It?
Larger fish prey on queen angelfish.

Queen angelfish

Social Organization

These shy fish are found alone or in pairs.

Life Cycle

Mating pairs bring their bellies close together and release clouds of sperm and egg. The female can release thousands of eggs each time she mates. The fertilized eggs are transparent and they float until they hatch into larvae in 15-20 hours. The larvae initially lack eyes, fins and digestive organs but within 48 hours they develop the physical characteristics that allow them to swim. The larvae feed on plankton growing rapidly for about a month reaching one half to three quarters of an inch (15-20 mm) in length. They settle on the bottom of the reef where they continue to grow. Juveniles are not brightly colored like the adult angelfish. The young queen angelfish feed by cleaning parasites from larger fish. Average lifespan in the wild is up to 15 years.

False Percula Clownfish

Amphiprion percula

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Clownfish have adapted to life on the reef by developing a symbiotic relationship with the anemones. Clownfish are small and would be preyed upon by larger fish if they were not living within and protected by the stinging tentacles of the anemone. The clownfish is covered with a specialized mucous that gives it immunity from the sting cells on the host anemone. Safe within the anemone tentacles, the clownfish can feed on planktonic organisms that float by.

Classification

CLASS:Osteichthyes
ORDER:Perciformes
FAMILY:Pomacentridae
GENUS:Amphiprion
SPECIES:percula

Habitat & Range

This genus of fish inhabits shallow sunlit tropical reefs with an abundance of anemones. Here the depth rarely exceeds 39 feet (12 m) and water temperature ranges between 77-82.4 Fo (25-28 Co).

Clownfish are native to the warm waters of the Indian and Pacific Oceans including the Great Barrier Reef and the Red Sea.

Location

clownfish swimming through anemone
clownfish swimming
clownfish swimming through ane
clownfish swimming through anemone
clownfish swimming
clownfish swimming through ane

Adaptations

  • Anemones Depend on Clownfish
  • The symbiotic relationship between clownfish and anemones also benefits the anemone. The clownfish drives away hungry butterfly fish that would nibble on the anemone’s tentacles. The clownfish also “preen” the anemone’s tentacles by cleaning up the leftovers, waste material and debris that might clutter up the anemone and invite parasites and algae. The clownfish also draws potential prey into the tentacles where it is stung and eaten by the anemone.
  • Clownfish Depend on Anemones
  • Clownfish have adapted to life on the reef by developing a symbiotic relationship with the anemones. Clownfish are small and would be preyed upon by larger fish if they were not living within and protected by the stinging tentacles of the anemone. The clownfish is covered with a specialized mucous that gives it immunity from the sting cells on the host anemone. Safe within the anemone tentacles, the clownfish can feed on planktonic organisms that float by.

Physical Description

  • Clownfish are up to three and a half inches (8.9 cm) long.
  • They most often have color patterns in orange, red or black with white bars or patches.
  • Their bodies are covered with scales.
  • They have fins and gills.

Diet

What Does It Eat?

In the wild:
Algae, invertebrates and planktonic organisms.

At the zoo:
Mysis shrimp, algae and flake fish food.

What Eats It?
Other larger fish prey on all species of clownfish.

clownfish swimming through anemone

Social Organization

Clownfish live in small groups inhabiting a single anemone. The group consists of a dominant breeding pair cohabiting with a few non-reproductive adult and juvenile clownfish. They aggressively defend their territory, bullying others away from their host anemone.

Life Cycle

Within a small group of clownfish only the dominant male and female clownfish mate. The female then lays 300-700 eggs on the rocky area beneath the host anemone. The eggs are cared for by the male who routinely fans them, circulating the water and increasing the oxygen supply. He cleans away debris and mouths the eggs, removing any dead eggs. The eggs hatch at night after six to seven days of incubation. The offspring, called “fry,” are all male and they are tiny (one-tenth inch or 3-4 mm). The clownfish fry float away, joining the plankton that travels with the ocean currents. After 15 days of floating, eating and growing, they are ready to bond with a host anemone. Juvenile clownfish live and feed mainly around the fringes of an anemone’s tentacles. If the breeding female dies, the adult male has the biological ability to change sex and over a couple of weeks, become a female. Meanwhile the biggest of the juvenile males steps up to replace the breeding male and they form a new breeding pair. This unique adaptation ensures the continuation of the species. The lifespan of clownfish is unknown.

Archerfish

Toxotes jaculator

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Most fish that feed on insects must rely on them falling, landing or being blown into the water. The archerfish has an adaptation that enables it to shoot and catch insect prey. In fact, they are known as “spitting sharpshooters,” able to shoot down insects up to five feet (1.5 m) above the water by spitting a jet of water from its mouth. This is amazing given the index of refraction compensation necessary for accurately aiming through the water-air interface.

Classification

CLASS:Actinopterygii
ORDER:Perciformes
FAMILY:Toxotidae
GENUS:Toxotes
SPECIES:jaculator

Habitat & Range

Archerfish inhabit river estuaries and brackish coastal waters of Asia and in the mangrove swamps and rover mouths of northern Australia. The archerfish swim among the roots, preying on insects that land on the vegetation.

They are found in southeast Asia, from India to the Philippines, Indonesia, Vanuatu, the Solomon Islands and New Guinea. Some species are found in northern Australia.

Location

Archerfish
Side by side archerfish
Archerfish
Archerfish
Archerfish
Archerfish
Side by side archerfish
Archerfish
Archerfish
Archerfish

Adaptations

Spitting sharpshooters

Most fish that feed on insects must rely on them falling, landing or being blown into the water. The archerfish has an adaptation that enables it to shoot and catch insect prey. In fact, they are known as “spitting sharpshooters,” able to shoot down insects up to five feet (1.5 m) above the water by spitting a jet of water from its mouth. This is amazing given the index of refraction compensation necessary for accurately aiming through the water-air interface.

“Shooting” is made possible because archerfish have specially adapted mouths and eyesight. They have an elongated mouth that has an internal channel through which water can be forcefully pumped using powerful jaw muscles. There is a deep grove that runs along the roof of the mouth and a ridge along the top of the tongue that fits into this groove. When an archerfish shoots a jet of water, it raises its tongue against the roof of the mouth forming a tube (like the barrel of a gun). The gill covers are then quickly closed which forces the water along the tube. The tip of the tongue acts as a valve.

Their eyes face forward, giving better binocular vision to judge distances accurately. When it spots a potential target, the archerfish tries to swim directly beneath it to minimize distortion. Its body shape combined with the dorsal fin well back on the body, allows the fish to swim very close to the surface and look upwards without creating surface disturbance. Once in range, the archerfish fires a jet of water, knocking the victim off its perch and into its waiting jaws. It shoots its jet with such force that it stings if it hits human flesh. When the fish fails to shoot down its prey, it is able to leap out of the water (up to one foot) to snatch the insect.

Physical Description

  • Archerfish are small surface-dwelling fish with a very distinctive appearance.
  • All six species are deep bodied, laterally compressed fish with large, forward facing eyes and a flattened head.
  • They have small scales that extend onto their fins with a single dorsal fin near the rear.
  • Their profile from the tip of the snout to the dorsal fins is almost straight.
  • Their coloration is white or silvery with black dorsal banding, usually five to seven bands.
  • Maximum length is approximately 12 inches (25 cm).
  • They have a large protractile mouth with a grooved palate and large projectile jaws; their lower jaw is longer than their upper jaw.

Diet

What Does It Eat?

In the wild:
Archerfish are essentially carnivorous. Their diet is mainly insects, small aquatic crustaceans, insect larvae and zooplankton. Some floating vegetable material such as plants pollen, flower buds and pulpy fruits and also ingested.

At the zoo:
Fish pieces, insects and insect larvae.

Side by side archerfish

Social Organization

Juveniles congregate in calm water in small schools of a dozen or so, swimming just below the surface around submerged roots, sunken debris and below overhanging branches. Adults may roam considerable distances along the shoreline sometimes hunting in groups of four or five. Archerfish are diurnal, most active during the day when there is enough light to see its prey through the murky swamp water. At night it rests motionless among the mangrove roots and debris, which offer some protection from large predators.

Life Cycle

The fry hatch and drift downstream toward the swamp, where they gather in small schools in the shelter of overhanging branches. Individuals attain three to four inches (7-9 cm) in length after about six months. The young must learn to hunt for themselves, since the mature fish do not raise them. It takes time before the juvenile’s master shooting their water jets with any accuracy. In the meantime, they will eat zooplankton and small insects like mosquitoes and gnats floating on the surface to survive. Many fry are eaten by larger fish so few survive the one to two years they need to become mature adults.

Blind Cave Fish

Astyanax mexicanus

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Blind cave fish compensate for their lack of sight by having a more sensitive lateral line system which detects vibrations or changes in pressure in the water. The lateral line is a specialized sensory organ found in fish. It is a canal system running just under the skin along each side of the fish’s body.

Classification

CLASS:Osteichthyes
ORDER:Characiformes
FAMILY:Characidae
GENUS:Astyanax
SPECIES:mexicanus

Habitat & Range

This species of fish lives in warm dark caves of freshwater rivers, lakes or pools.

Blind cave fish are found throughout Central America.

Location

Map of Americas

Blind cave fish
Blind cave fish and baby
3 blind cave fish
Blind cave fish
Blind cave fish
Blind cave fish and baby
3 blind cave fish
Blind cave fish

Adaptations

Covered with Scales

The blind cave fish has skin covered with a layer of scales arranged in head-to-tail pattern, similar to shingles on a roof. These scales play a protective role for the fish and reduce drag when swimming. Fish also secrete a layer of mucus that covers their body, further reducing drag in the water. The mucus also helps prevent infection by serving as a barrier to microorganisms and also makes the fish slippery and difficult for predators to catch.

Detecting Vibrations

Blind cave fish compensate for their lack of sight by having a more sensitive lateral line system which detects vibrations or changes in pressure in the water. The lateral line is a specialized sensory organ found in fish. It is a canal system running just under the skin along each side of the fish’s body. This canal is lined with special receptors that are quite sensitive to vibrations and water currents and thus it is an “extended sense of touch” allowing the blind cave fish to detect obstacles at a distance. Using this heightened sense helps blind cave fish find food and avoid bumping into obstacles.

Physical Description

  • Blind cave fish grow up to three and a half inches (8.9 cm) long. Females are slightly larger and plumper than males.
  • Their minnow-shaped body lacks pigment, leaving it cream or light pink in color.
  • They have scales on their body.
  • Their eye sockets are covered with scales and appear as dark spots.
  • These fish have small adipose fin present between the dorsal and caudal fins.

Diet

What Does It Eat?

In the wild:
Blind cave fish are excellent scavengers and will eat almost anything. They often feed on animal and plant remains swept into caves

At the zoo:
Flake fish food.

What Eats It?
Other larger fish prey on blind cave fish.

3 blind cave fish

Social Organization

Blind cave fish are found in large groups called “schools.”

Life Cycle

The blind cave fish has an elaborate courtship during which the male and female make exaggerated movements of the mouth and gills. Presumably the turbulence these movements produce helps the fish locate a partner; male and female swim side-by-side and then mate. Fertilized eggs sink to the bottom where they stick to rocks. Blind cave fish growing within eggs have normally developing eyes early on, but the eyes will start to degenerate within the egg. The fish may be born blind or it may be born with functional eyes which later cloud over and shrink because there is no light in the dark caves and eyesight is not necessary. The lifespan of the blind cave fish is approximately ten years.

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