gaint Chinese Sturgeon

A pair of Chinese sturgeons swim in the Beijing City Aquarium in China. Capable of weighing half a ton and growing to 16 feet (5 meters) long, this freshwater leviathan is one of the largest sturgeon species on Earth. River damming in China has caused its numbers to plummet, and it is listed as an endangered species.

                                                         Photograph courtesy Zeb Hogan


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 shark like 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.

the gaint barb fish

A boy poses with a giant barb on the Tonle Sap River near Phnom Penh, Cambodia. The fish, landed as bycatch by a local fishing operation, was tagged and released as part of a study of large freshwater species in the Mekong River Basin. There is evidence that giant barb once reached sizes of 10 feet (3 meters) long and 660 pounds (300 kilograms), but today specimens even half that size are extremely rare.

                                                        Photograph courtesy Zeb Hogan


Sometimes called the "king of fish," the giant barb has a storied history in its Southeast Asia range.In Vietnam, this distinctive, large-headed species is called cá ho.In Cambodia, the barb appears in ancient temple carvings at Angkor and has been named the national fish.The giant barb is a river fish that often frequents deep pools
but may move seasonally into canals or river floodplains.

Juveniles are often seen in swamps or smaller river tributaries.Though they've been known to reach 660 pounds (300 kilograms), specimens above 220 pounds (100 kilograms) have become exceptionally
rare in recent years.

These massive fish sustain their bulk on tiny plants such as phytoplankton as well as algae, seaweed, and, during periods of high water, the fruits of submerged terrestrial plants.

Scientists fear that cá ho populations have declined to the point where few survive to reach the age of sexual reproduction. This fish has become severely threatened along its native range, which stretches from Cambodia to the Mekong Delta, because of water pollution, river traffic, and especially overfishing pressures.

The flesh of the giant barb has long been considered a delicacy among residents of the Mekong River Basin, and it is a popular eating and pickling option for the tens of millions of people who depend on the Mekong's aquatic fauna for food.

Government programs have focused on captive breeding in an attempt to save this regional icon. Young giant barb can become acclimated to pond life and may be suitable for farming.

Mekong Giant Catfish

One of the largest fish in the world, Mekong giant catfish, such as this one on a fisherman's boat, can reach 10 feet (3 meters) long and weigh up to 650 pounds (300 kilograms). This critically endangered species has suffered from overfishing, dam building, and habitat destruction.

Photograph courtesy Zeb Hogan



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.
 

largest freshwater arapaima fish in the world

A diver shares a tank with an adult arapaima fish at an aquarium in Manaus, Brazil. Known as the pirarucu in Brazil and the paiche in Peru, this South America giant is one of the largest freshwater fish in the world. Some reach lengths of more than 10 feet (3 meters) and weigh upward of 400 pounds (180 kilograms).

Photograph courtesy Zeb Hogan

The arapaima is an air-breathing fish that plies the rain forest rivers of South America's Amazon Basin and nearby lakes and swamps. One of the world's largest freshwater fish, these giants can reach 9 feet (2.75 meters) long and weigh up to 440 pounds (200 kilograms). They have a wide, scaly, gray body and a tapered head.

Though arapaimas can stay underwater for 10 to 20 minutes, they tend to remain near the water's surface, where they hunt and emerge often to breathe with a distinctive coughing noise. They survive mainly on fish but are known to occasionally grab birds close to the water's surface.

The arapaima's proximity to the water's surface make it vulnerable to human predators, who can easily target them with harpoons. Some indigenous communities consume the arapaima's meat and tongue and collect its large scales, which are fashioned into jewelry and other items.

The Amazon's seasonal floods have become part of the arapaima's reproductive cycle. During low-water months (February to April) arapaimas construct bottom nests and females lay eggs. Young begin to hatch as rising water levels provide them with flood conditions in which to flourish. Adult males play an unusual reproductive role by incubating tens of thousands of eggs in their mouths, guarding them aggressively and moving them when necessary.

While this giant fish's habitat is relatively unmolested, overfishing has become a serious problem, and some South American authorities have attempted to enact protections.

world's largest freshwater giant stingray.

Fish experts believe the giant stingray, such as this one in Cambodia's Mekong River, is the largest freshwater species on Earth. This specimen measured more than 13 feet (4 meters) long.

Photograph courtesy Zeb Hogan


The giant stingray is one of the world's largest freshwater fish, but it's also cloaked in mystery.No one is sure how many giant stingrays are left, which habitats they prefer, or even if they ever venture into the ocean, where their more commonly known relatives dwell.

These ancient fish, little changed over many millions of years, can reach 16.5 feet (5 meters) long and weigh up to 1,320 pounds (600 kilograms). They are brown to gray in color, wide and flat in form, and they sport a long, whiplike tail.

Giant stingrays are known to prowl river systems in Thailand, Borneo, New Guinea, and northern Australia.
They often bury themselves in sandy or silted river bottoms and breathe through holes, or spiracles, located on top of their bodies. Stingrays locate prey, usually clams and crabs, with a sensor that can detect an animal's electrical field.

Stingray numbers appear to have dropped dramatically in recent years as their riverine habitats have degraded, and it appears they no longer inhabit some parts of their historical range. Large stingrays have been known to pull boats upstream and even underwater.

Though stingrays do not readily attack humans, they are one of the few megafishes that can pose a real danger to those who handle them. Each ray sports a deadly barb on the base of its tail that can easily penetrate human skin and even bone, much like a hunting arrow. This stinger can be as long as 15 inches
(38 centimeters) and typically introduces toxins to the victim's wound.