Sharks & other fish

Bony Fish (Teleosts)

Bony fish are found around the world in both salt and fresh water, from the tropics to the Arctic and Antarctic, and from the coasts to the deepest parts of the ocean. They range in size from the pygmy goby, at one-third of an inch (9 millimeters), to the marlin, which can grow to nearly 12 feet (3.5 meters).

The behaviors and life cycle strategies of fish is almost as varied as the number of species. Some fish can survive being frozen for long periods, while others have adapted to life near hydrothermal vents. Some fish have even evolved mechanisms to deal with high levels of pollution.

Cartilaginous Fish (Elasmobranchs)

Sharks, skates, and rays are also found around the world and, unlike bony fishes, have a skeleton made of cartilage. They also lack the swim bladder found in other fish species, often relying instead on a large, oily liver to control their buoyancy.

There are about 500 species of sharks, several of which are among the most recognizable fish species on Earth, including the white shark, one of the ocean's largest predators, and the whale shark, which is the largest fish in the ocean. Because they are wide-ranging animals, many basic questions about sharks remain unanswered, including where many species migrate, when and where they mate and give birth, and what they eat. This lack of information has made it difficult to estimate shark populations and challenging to design conservation measures for even the most threatened species.

Sharks are generally slow to mature—white sharks likely take at least 20 years to reach reproductive age—and only produce two to ten pups per litter. This means shark populations are especially vulnerable to human activities such as fishing. Each year, between 50 and 100 million sharks are killed, mainly for their fins, which are used to make a traditional Chinese soup. This level of harvesting is unsustainable and has dramatically reduced populations of many shark species around the world.