By far one of the most colorful and diverse groups of animals in the sea is that of the coral reef fishes. Their extensive range of bright colors and bold patterns is virtually unmatched in the entire undersea kingdom. And although they may be beautiful to behold, there is a real function behind each of these designs. Red colors appear black under water, helping a fish to go unseen. Stripes allow a fish to camouflage itself against the coral. Spotted patterns serve to confuse a would-be predator. Each species of fish deals with survival in its own way, and we are left to wonder at their accomplishments.
Over 365 species of coral reef fish belonging to 61 families have been recorded in the Gulf of Thailand and around Koh Tao (Scaps, 2006). This includes many small colorful fishes found amongst the corals, as well as the world’s biggest fish, the Whale Shark. This number is climbing though.
The first fishes are believed to have evolved about 500 million years ago, the most primitive fishes that we find today are called jawless fishes, which include Hagfish and lampreys. These fish lack the bone or cartilage that we associate with most vertebrates, and illustrate the link between our invertebrate and vertebrate groups. Slightly more advanced are the cartilaginous fishes, which is a very ancient group having a flexible skeleton made of cartilage instead of bone. This group includes families of fish such as the sharks and rays, which are some of the reef’s top predators.
The reefs are significant to the survival of some endangered species. Coral reefs form complex ecosystems with tremendous biodiversity. About 25% of marine fish species settle in the coral reef that only occupies less than 1% of the surface area of the world oceans.
Coral Reefs are home to so many fish and coral species – they come in all shapes, sizes and colours! Here’s a guide to some of the colourful and quirky creatures you might meet on your snorkel or dive trip.
Moray eels - Family Muraenidae
Moray eels are actually a type of bony fish, they are not related to snakes as some may infer. There are over 200 species of moray eels worldwide, but the most common species on Koh Tao is the White Eyed Moray Eel. Moray eels have a serpentine shape, and live in burrows or crevices and holes in corals and rocks. They feed on crustaceans, mollusks, and small fish. They are nearly top-predators, but sometimes become prey for barracuda or sea snakes. As predators, eels are important in regulating the balance of the reef. They are also sensitive to habitat destruction and declines in water quality.
Banded and Foureye Butterflyfish
The banded butterflyfish (Chaetodon striatus) and the foureye butterflyfish (Chaetodon capistratus) are only two of the numerous species of butterflyfish found on Caribbean reefs. You can easily distinguish the banded butterflyfish by the black bars (vertical stripes) on its sides. In contrast, the foureye butterflyfish has pinstripe diagonal lines running across its body. The foureye butterflyfish’s most recognizable feature is two large spots near the back of its body, one on each side. These two spots mimic the appearance of eyes, giving the foureye butterflyfish its name.
Butterflyfish of all species can be distinguished from angelfish, which also have rounded, flat, disc-like bodies, by the length of their anal and dorsal (top and bottom) fins. Most angelfish have anal and dorsal fins that extend past the tip their tail fins, while most butterflyfish do not. Butterflyfish are usually seen in pairs fluttering above shallow reefs.
Clown Triggerfish (Balistoides conspicillum)
The clown triggerfish is without a doubt the most beautiful member of the trigger family. The bright yellow mouth is believed to deter potential predators. As with most other triggers, the clown is an aggressive feeder, feeding mainly on crustaceans and mollusks. They use their strong jaws to crack open the shells of mollusks and crabs.
Parrot Fish is the most easily recognized due to their teeth. The teeth fuse together, which is very unique and quite useful for scratching algae off the surface of the coral. Parrot fish also feed on soft and hard corals. Their teeth help them chew the corals.
There are more than thirty species of parrot fish on the Great Barrier Reef. They vary in colors and patterns, including blues, greens, and yellows. They are one of the most visible species in the Great Barrier Reef. Snorkelers could easily see them in the Great Barrier Reef.
Another peculiar habit about parrot fish is that they use their teeth to triturate coral and excrete them as sand. It’s said that about 30% of the coral sand you see at the reef is parrot fish excretion.
Squirrelfish (Holocentrus adscensionis) have spiky fins and big dark eyes. They are nocturnal and use their big, sensitive eyes to hunt for prey in minimal light. You can typically find these night owls loafing around in dark areas of the reef during the day, but you can see them in the open on night dives. A variety of squirrelfish species can be found in the Caribbean, and while they all have distinctive features, most species have reddish bodies, silver or golden horizontal stripes, and big spiky dorsal fins.
Hawkfishes are a group of coral reef fishes that have a peculiar habit of resting or perching on corals and rocks as they wait for their prey. They feed on shrimps and small fish. They are not very good swimmers, and their comic antics make them an enjoyable addition to the home aquarium. This species is characterized by the vertical red stripes, which help with camouflage.
The porcupinefish (Diodon hystrix) is a large, white pufferfish covered with long spines. Divers needn’t fear a porcupinefish’s quills—porcupinefish are slow-moving, docile giants with huge, doll-like eyes and wide mouths. Like other pufferfish, the porcupinefish can puff up by filling with water when threatened. The quick change in size not only startles predators, but it also makes the porcupinefish a difficult size and shape to eat. As a further defense, inflation causes a porcupinefish’s spines to protrude out perpendicular to its body.
The queen angelfish is without a doubt the most beautiful of the angelfish species. Young queens resemble a juvenile blue angelfish. But as they grow, they acquire their spectacular blue and yellow markings, with rainbow colors on the edges of their fins. The queen angelfish is found throughout the western Atlantic. It is a grazer, feeding on algae, sponges, and coral.
The percula is one of the most beautiful of the clownfish species. The contrasting orange, white, and black colors make it a favorite among aquarium hobbyists. The percula is found in the waters of the Indo-Pacific, where it feeds on plankton and small crustaceans. Like all clownfishes, it will make its home in the tentacles of several anemone species.
Rabbit fish - Family Siganidae
Rabbit fish are a common reef fish, and resemble the simple fish profile that everyone can recognize. They have a nose which resembles a rabbit, and also play a very similar ecological role to rabbits. The 3 most common species on Koh Tao are: the Double Barred Rabbitfish, the Java RabbitFish, and the Gold Saddle Rabbitfish.Rabbit fish are important reef herbivores feeding on benthic algae. They are also an important fish as prey for sharks and food for humans.Rabbit fish have poisonous spines and should be handled carefully when removed from nets when found while diving. At night rabbit fish can be found sleeping with their dorsal and anal fin spines extended, making them a more difficult meal for nocturnal predators.
Many divers recognize blue tangs (Acanthurus coeruleus) as Dori, the fish character from the Disney movie “Finding Nemo.” These small round blue or purple fish are a type of surgeonfish, so-named because of the small yellow spike where the tail meets the body. This extremely sharp spine can be thought of as a surgeonfish’s scalpel. Like many fish, blue tangs can darken or lighten to provide camouflage with their surroundings. Blue tangs are frequently seen in schools grazing on plant life. Divers frequently observe large groups of blue tangs moving over slowly the reef as they snack on bits of algae.
Pink Skunk Clownfish
The pink skunk clownfish is identified by its soft, pale pink color and the single white band behind its head. Found in the Pacific Ocean, this clownfish feeds on plankton and small crustaceans. Clownfishes are very aggressive and territorial. These small 3-inch fish have been known to attach sharks and divers who wander too close to their host anemone.
Lionfish (Pterois volitans), while beautiful, are an invasive species from the Indo-Pacific that have become a common sight in the Caribbean. With no natural predators in the Caribbean, lionfish populations have skyrocketed over recent years. Lionfish feed on young reef fish that have not yet had the opportunity to reproduce. This has decimated reef fish populations in many areas of the Caribbean.
Fire Fishes are characterized by their bright colors and by their unusually elongated dorsal fin. This fin is used as a signaling device to communicate with other fire fishes. It is also used by the fish to wedge itself into small crevasses as a means of protection from predators. Fire fishes are found throughout the Indo-Pacific.
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Coral reef fish live amongst or in close relation to coral reefs. Most of them are very colorful. People love to observe the lovely fish. Even in a small area of coral reef, there could be hundreds of species. Coral reef fish have some unique characteristics. Have you ever wondered why they are so colorful? It’s coloration, which is a method of camouflage. Coloration can help coral reef fish rest within the right background, help them recognize species during mating, or threaten predators. The Great Barrier Reef fish are in all the colors of the rainbow: blue, red, orange, purple and green.
Reef fish have different body shapes from open water fish. To minimize friction when they move in the water, open water fish evolve the streamlined body. However, reef fish have flattened bodies. Compared with the speed, the maneuverability is more vital to reef fish. The flattened bodies help them change direction easier and faster.
Reef fish also have evolved complex adaptive behaviors. They hide in reef crevices or get together for social reasons. In this way, they can protect them from predators.