Sharks are diverse cartilaginous fish, varying significantly in size from the small dwarf lanternshark (17 centimeters) to the whale shark (12 meters), the largest fish globally. They inhabit a wide range of aquatic environments, from shallow coastal areas to the deep sea, and are found in all the world’s oceans. Their global distribution demonstrates adaptability to various conditions, including different temperatures and depths.
Prevalence in Tropical and Subtropical Seas
Many shark species thrive in the warmer waters of tropical and subtropical seas. These regions, characterized by consistent temperatures, support rich marine ecosystems like coral reefs and expansive open ocean environments. Sharks commonly found in these warm habitats include the great white shark, tiger shark, and various hammerhead and reef shark species. For instance, great white sharks are often found in coastal and offshore waters with temperatures between 12 and 24 degrees Celsius, with significant populations in areas like the United States, South Africa, and Australia.
Tiger sharks frequently inhabit tropical and warm temperate waters globally, including both shallow coastal areas and deeper oceanic zones. They generally prefer temperatures around 22 degrees Celsius or higher, supporting their active predatory lifestyle. Hammerhead sharks, particularly great hammerheads, are also common in warm temperate and tropical seas worldwide, often found in shallow waters near continental shelves and reefs.
How Temperature Influences Shark Biology
Water temperature significantly influences shark biology, affecting their metabolic rate, reproductive cycles, and the availability of their prey. As ectotherms, most sharks’ body temperatures align with their surrounding environment, meaning warmer waters generally lead to higher metabolic rates. This increased metabolism can accelerate digestion and necessitate a greater food intake, impacting their hunting behavior.
Temperature also plays a role in shark reproduction. Higher seawater temperatures can influence sex steroid levels, potentially triggering reproductive events such as ovulation and mating in some species. However, rising ocean temperatures can also negatively affect birthing processes, leading to shark pups being born smaller and with lower energy reserves. The distribution of prey, which sharks rely on, is also influenced by temperature, leading sharks to follow their food sources as ocean temperatures change.
Species Thriving in Cooler Oceans
While many sharks prefer warm waters, several species are well-adapted to and flourish in colder, temperate, or even polar environments. The Greenland shark is a notable example, inhabiting the North Atlantic and Arctic Oceans in waters ranging from just below freezing to about 7.4 degrees Celsius. These sharks exhibit adaptations such as a slow metabolism, which helps them conserve energy in their cold, food-scarce habitats. Their bodies also contain high concentrations of urea and trimethylamine N-oxide, which act as natural antifreezes.
The basking shark is another large species found in temperate oceans worldwide, including those with cooler temperatures. These filter feeders are often observed in waters between 7 and 16 degrees Celsius and migrate across ocean basins to areas with abundant plankton. The porbeagle shark is also found in cooler temperate waters and possesses regional endothermy, allowing it to maintain a body temperature higher than the surrounding water, supporting muscle function in colder conditions.