Mekong Giant Catfish

The world’s largest scaleless freshwater fish lives a tenuous existence in the murky brown waters of Southeast Asia’s Mekong River. Capable of reaching an almost mythical 10 feet (3 meters) in length and 650 pounds (295 kilograms), Mekong giant catfish live mainly in the lower half of the Mekong River system, in Cambodia, Laos, Thailand, and Vietnam. Once plentiful throughout the Mekong basin, population numbers have dropped by some 95 percent over the past century, and this critically endangered behemoth now teeters on the brink of extinction. Overfishing is the primary culprit in the giant catfish’s decline, but damming of Mekong tributaries, destruction of spawning and breeding grounds, and siltation have taken a huge toll. Some experts think there may only be a few hundred adults left. Mekong giant catfish have very low-set eyes and are silvery to dark gray on top and whitish to yellow on the bottom. They are toothless herbivores who live off the plants and algae in the river. Juveniles wear the characteristic catfish “whiskers,” called barbels, but these features shrink as they age. Highly migratory creatures, giant catfish require large stretches of river for their seasonal journeys and specific environmental conditions in their spawning and breeding areas. They are thought to rear primarily in Cambodia’s Tonle Sap lake and migrate hundreds of miles north to spawning grounds in Thailand. Dams and human encroachment, however, have severely disrupted their lifecycle. International efforts are under way to save the species. It is now illegal in Thailand, Laos, and Cambodia to harvest giant catfish. And recently in Thailand, a group of fishers pledged to stop catching giant catfish to honor the king’s 60th year on the throne. However, enforcement of fishing restrictions in many isolated villages along the Mekong is nearly impossible, and illicit and bycatch takings continue. Credits go to: National Geographic

The Beluga Whale

Belugas are also called white whales, and their unusual color makes them one of the most familiar and easily distinguishable of all the whales. Calves are born gray or even brown and only fade to white as they become sexually mature around five years of age. White whales are smallish, ranging from 13 to 20 feet (4 to 6.1 meters) in length. They have rounded foreheads and no dorsal fin. Belugas generally live together in small groups known as pods. They are social animals and very vocal communicators that employ a diversified language of clicks, whistles, and clangs. Belugas can also mimic a variety of other sounds. These whales are common in the Arctic Ocean's coastal waters, though they are found in subarctic waters as well. Arctic belugas migrate southward in large herds when the sea freezes over. Animals trapped by Arctic ice often die, and they are prey for polar bears, killer whales, and for Arctic people. They are hunted by indigenous people of the north, and by commercial fisheries that brought some populations, such as those in the Gulf of St. Lawrence, to near collapse. Beluga feed on fish, crustaceans, and worms. The whale is related to the tusked "unicorn" whale known as the narwhal. The beluga is not related to the sturgeon of the same name, which has been heavily fished for its famous caviar. Credits go to: National Geographic

Chinese Sturgeon

Chinese sturgeons are seasoned travelers, undertaking a round-trip journey of some 2,000 miles (3,500 kilometers) every year from the East China Sea to their spawning grounds in the Yangtze River. But in recent years this ancient cycle has been blocked by the Gezhouba Dam, built in the 1980s. Since that time subsequent dams have placed new, possibly insurmountable, hurdles in the sturgeons' upstream path and thrown the future of the species into serious doubt. Heavy shipping traffic, overfishing, and water pollution have also plagued Yangtze River waters and taken a heavy toll on these aquatic behemoths. Some scientists think fewer than a thousand individuals may remain. Chinese sturgeons can grow to enormous proportions, with large specimens topping 16 feet (5 meters) and 1,000 pounds (450 kilograms). These prehistoric-looking giants have a sharklike form, with large pectoral fins, a rounded snout, and rows of pronounced ridges running the length of their spine and flanks. Chinese officials have made efforts to safeguard the sturgeon, including curtailed fishing and the creation of a conservation area below the Gezhouba Dam to serve as an alternative spawning ground. They've also attempted to replenish the fish's dwindling numbers by breeding millions of fry in captivity and releasing them into their native rivers. So far such efforts have met with little success.Sturgeons may face long odds, but the fish has survival in its genes. Sturgeons have lived in the Yangtze for perhaps 140 million years, and this relic of the dinosaur era is sometimes dubbed a "living fossil." Some reports suggest the sturgeon may already be adapting to its changing environment. Studies suggest its diet is shifting from less abundant bottom dwellers, like clams, to more plentiful earthworms.
Credits go to: National Geographic

Sun Fish

As gigantic as the ocean sunfish can be, it still seems like only half a fish.
Sunfish, or mola, develop their truncated, bullet-like shape because the back fin which they are born with simply never grows. Instead, it folds into itself as the enormous creature matures, creating a rounded rudder called a clavus. Mola in Latin means "millstone" and describes the ocean sunfish’s somewhat circular shape. They are a silvery color and have a rough skin texture. The mola are the heaviest of all the bony fish, with large specimens reaching 14 feet (4.2 meters) vertically and 10 feet (3.1 meters) horizontally and weighing nearly 5,000 pounds (2,268 kilograms). Sharks and rays can be heavier, but they're cartilaginous fish. Mola are found in temperate and tropical oceans around the world. They are frequently seen basking in the sun near the surface and are often mistaken for sharks when their huge dorsal fins emerge above the water. Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths. Ocean sunfish can become so infested with skin parasites, they will often invite small fish or even birds to feast on the pesky critters. They will even breach the surface up to 10 feet (3 meters) in the air and land with a splash in an attempt to shake the parasites. They are clumsy swimmers, waggling their large dorsal and anal fins to move and steering with their clavus. Their food of choice is jellyfish, though they will eat small fish and huge amounts of zooplankton and algae as well. They are harmless to people, but can be very curious and will often approach divers. Their population is considered stable, though they frequently get snagged in drift gill nets and can suffocate on sea trash, like plastic bags, which resemble jellyfish.
Credits go to: National Geographic

Queen Angelfish

Queen angelfish get their royal title from the speckled, blue-ringed black spot on their heads that resembles a crown. Decked out with electric blue bodies, blazing yellow tails, and light purple and orange highlights, Queen angels are among the most strikingly colorful of all reef fishes. Their adornments seem shockingly conspicuous, but they blend well when hiding amid the exotic reef colors. They are shy fish, found either alone or often in pairs in the warm waters of the Caribbean and western Atlantic. Fairly large for reef-dwellers, they can grow up to 18 inches (45 centimeters) in length. They have rounded heads and small beak-like mouths, and, like other angelfish, their long upper and lower fins stream dramatically behind them. Their diet consists almost entirely of sponges and algae, but they will also nibble on sea fans, soft corals, and even jellyfish. Queen angels are close relatives of the equally striking blue angelfish. In fact, these two species are known to mate, forming natural hybrids, a very rare occurrence among angelfish.
They are widely harvested for the aquarium trade, but are common throughout their range and have no special protections or status. Credits go to: National Geographic

Parrot Fish

It's hard to decide which of the colorful parrot fish's many unique characteristics is most remarkable. There’s its diet, which consists primarily of algae extracted from chunks of coral ripped from a reef. The coral is pulverized with grinding teeth in the fishes’ throats in order to get to the algae-filled polyps inside. Much of the sand in the parrot fish's range is actually the ground-up, undigested coral they excrete. There's its gender, which they can change repeatedly throughout their lives, and their coloration and patterns, which are a classification nightmare, varying greatly, even among the males, females, and juveniles of the same species.
Finally, there are the pajamas. Every night, certain species of parrot fish envelope themselves in a transparent cocoon made of mucous secreted from an organ on their head. Scientists think the cocoon masks their scent, making them harder for nocturnal predators, like moray eels, to find. Close relatives of the wrasse, parrot fish are abundant in and around the tropical reefs of all the world’s oceans. There are about 80 identified species, ranging in size from less than 1 to 4 feet (30 to 120 centimeters) in length. Their meat is rarely consumed in the United States, but is a delicacy in many other parts of the world. In Polynesia, it is served raw and was once considered "royal food," only eaten by the king.
Credits go to: National Geographic

Lionfish

Pretty much everything about the venomous lionfish—its red-and-white zebra stripes, long, showy pectoral fins, and generally cantankerous demeanor—says, "Don't touch!"
The venom of the lionfish, delivered via an array of up to 18 needle-like dorsal fins, is purely defensive. It relies on camouflage and lightning-fast reflexes to capture prey, mainly fish and shrimp. A sting from a lionfish is extremely painful to humans and can cause nausea and breathing difficulties, but is rarely fatal.
Lionfish, also called turkey fish, dragon fish and scorpion fish, are native to the reefs and rocky crevices of the Indo-Pacific, although they've found their way to warm ocean habitats worldwide. The largest of lionfish can grow to about 15 inches (0.4 meters) in length, but the average is closer to 1 foot (0.3 meters). Lionfish are popular in some parts of the world as food, but are far more prized in the aquarium trade. Their population numbers are healthy and their distribution is growing, causing some concerned in the United States, where some feel the success of this non-indigenous species presents human and environmental dangers.
Credits go to: National Geographic

Butterfly Fish

Butterflyfish, with their amazing array of colors and patterns, are among the most common sites on reefs throughout the world. Although some species are dull-colored, most wear intricate patterns with striking backgrounds of blue, red, orange, or yellow. Many have dark bands across their eyes and round, eye-like dots on their flanks to confuse predators as to which end to strike and in which direction they're likely to flee. There are about 114 species of butterflyfish. They have thin, disk-shaped bodies that closely resemble their equally recognizable cousins, the angelfish. They spend their days tirelessly pecking at coral and rock formations with their long, thin snouts in search of coral polyps, worms, and other small invertebrates. Some butterflyfish species travel in small schools, although many are solitary until they find a partner, with whom they may mate for life. Credits go to: National Geographic

Pufferfish

Biologists think pufferfish, also known as blowfish, developed their famous “inflatability” because their slow, somewhat clumsy swimming style makes them vulnerable to predators. In lieu of escape, pufferfish use their highly elastic stomachs and the ability to quickly ingest huge amounts of water (and even air when necessary) to turn themselves into a virtually inedible ball several times their normal size. Some species also have spines on their skin to make them even less palatable. A predator that manages to snag a puffer before it inflates won’t feel lucky for long. Almost all pufferfish contain tetrodotoxin, a substance that makes them foul tasting and often lethal to fish. To humans, tetrodotoxin is deadly, up to 1,200 times more poisonous than cyanide. There is enough toxin in one pufferfish to kill 30 adult humans, and there is no known antidote. Amazingly, the meat of some pufferfish is considered a delicacy. Called fugu in Japan, it is extremely expensive and only prepared by trained, licensed chefs who know that one bad cut means almost certain death for a customer. In fact, many such deaths occur annually. There are more than 120 species of pufferfish worldwide. Most are found in tropical and subtropical ocean waters, but some species live in brackish and even fresh water. They have long, tapered bodies with bulbous heads. Some wear wild markings and colors to advertise their toxicity, while others have more muted or cryptic coloring to blend in with their environment. They range in size from the 1-inch-long (2.5-centimeter-long) dwarf or pygmy puffer to the freshwater giant puffer, which can grow to more than 2 feet (61 centimeters) in length. They are scaleless fish and usually have rough to spiky skin. All have four teeth that are fused together into a beak-like form. The diet of the pufferfish includes mostly invertebrates and algae. Large specimens will even crack open and eat clams, mussels, and shellfish with their hard beaks. Poisonous puffers are believed to synthesize their deadly toxin from the bacteria in the animals they eat. Some species of pufferfish are considered vulnerable due to pollution, habitat loss, and overfishing, but most populations are considered stable. Credits go to: National Geographic