By Blaise Jones
Sharks possess a very adaptable physiology which lets them thrive in almost any environment the ocean has to offer. Warm or cold water, deep and shallow depths, saltwater, fresh water – there are sharks for in every environment and habitat.
Around the World
Sharks can be found in almost every ocean in the world. The oceans of the world can be roughly placed into one of four categories: tropical, warm temperate, cold temperate, and polar. Sharks can be found in all of these regions, though their abundance varies. The vast majority of sharks can be found in warm temperate waters, where nearly every species of shark has been observed. The regions with the second highest concentration of shark species are the tropical regions, where approximately 450 species have been observed. An estimated 200 species have been observed in the cold temperate regions, and five species are known to live in the Arctic. The only region where sharks have not been observed is in the Southern Ocean around Antarctica.
Since many sharks are migratory, they are often observed across multiple different regions. This is why the total numbers of sharks observed per region is higher than the estimated total number of shark species.
Fair Weather Fish
The vast majority of sharks live in temperate, shallow waters with lots of structure such as coral reefs or seagrass beds. Sharks are drawn to these environments because they are the ideal conditions for the fish that sharks prey upon. Sharks occupy all levels of the water column in these shallow seas.
While some species of shark stick to one basic depth in the water column, such as whitetip reef shark, others travel freely up and down the column, such as hammerhead sharks. Some sharks, such as tiger sharks, have routine schedules of deep water to shallow water migration, which follow a day and night cycle.
Living to the Extreme
Due to their robust physiologies, sharks have been observed in some of the most inhospitable and unexpected places. Frilled and goblin sharks can both be found at depths reaching 4,300 feet (1,311 m) where no light penetrates, creating an aquatic habitat that is pitch black. The great lanternshark holds the record for the deepest that a shark species has been observed, plummeting to 14,763feet (4,500 m).
Lemon sharks and blacktip reef sharks can be found in water so shallow that the tops of their bodies break the surface.
Some sharks, such as the Greenland shark and porbeagle shark, can be found in the frigid waters of the Artic in. Hammerhead and silky sharks have been found swimming inside an active submerged volcano, Mount Kavachi in the Solomon Islands. The volcano is almost constantly erupting, greatly raising the acidity and temperature of the water.
While all species of shark live in salt water, the bull shark is able to swim in fresh water with no problem. In fact, there are several subspecies of bull shark that are entirely freshwater. These sharks can be found in Lake Nicaragua and in the Ganges, Mississippi, Tigris, and Zambezi Rivers.
“Sharks: The Mysterious Killers” by Downs Matthews
“The Encyclopedia of Sharks” by Steve Parker
“Sharks: The Animal Answer Guide” by Gene Helfman and George H. Burgess