Sharks inhabit the middle of the ocean, from sunlit surface waters to dark, high-pressure depths. The ocean’s vastness supports a diverse array of shark species, each adapted to specific conditions far from coastal areas. These open-ocean environments are dynamic habitats for many marine creatures.
Understanding the Open Ocean
The “middle of the ocean” refers to the pelagic zone, which encompasses the entire water column away from the coast and the seafloor. This expansive area contrasts with the neritic zone, which includes shallower waters over the continental shelf near land. The pelagic zone is the largest habitat on Earth, and it is further divided into several layers based on depth and light penetration.
The uppermost layer is the epipelagic zone, or sunlight zone, extending from the surface down to about 200 meters. This zone receives enough sunlight for photosynthesis, supporting a rich food web. Below this is the mesopelagic zone, or twilight zone, from 200 to 1,000 meters, where light is faint. Deeper still are the bathypelagic (midnight zone), abyssopelagic (abyssal zone), and hadalpelagic zones (trenches). These deep zones are characterized by perpetual darkness, cold temperatures, and immense pressure.
Sharks of the High Seas
Many shark species inhabit the open, pelagic zones, far from any coastline. These “sharks of the high seas” are streamlined, built for speed and long-distance travel. They are top predators within their ecosystems and have few natural predators once fully grown.
The oceanic whitetip shark, identifiable by its long, paddle-like pectoral fins and distinctive white-tipped fins, is found in tropical and warm temperate seas. These sharks cruise slowly near the surface but can be opportunistic and aggressive when food is available, feeding on bony fish and cephalopods. Blue sharks are another widespread pelagic species, recognized by their slender bodies and iridescent blue coloration, known for extensive migrations across oceans. They primarily prey on small fish and squid, using speed to capture schooling prey.
Mako sharks are exceptionally fast predators, renowned for explosive bursts of speed. They primarily hunt fast-moving fish like tuna and swordfish. The largest fish in the ocean, the whale shark, is a pelagic dweller, but unlike predators, it is a filter feeder. Whale sharks consume vast quantities of plankton, small crustaceans, and tiny fish by swimming with enormous mouths open, filtering water through specialized gill rakers. Another filter feeder, the basking shark, is the second-largest fish, found in temperate and boreal open waters, slowly swimming near the surface to filter plankton.
Why Sharks Roam Far From Shore
Sharks inhabit the open ocean for several reasons, primarily linked to food availability and migratory life cycles. The vastness of the pelagic zone provides ample space and resources for large, fast-moving predators requiring extensive hunting grounds. Many open-ocean sharks follow the migratory patterns of their prey, such as large schools of tuna or squid, which traverse vast oceanic distances.
These sharks are highly adapted to a nomadic lifestyle, constantly moving to find sufficient food. Their streamlined bodies enable efficient long-distance swimming, and some species, like the oceanic whitetip, must continuously swim to breathe. The open ocean also serves as an important environment for reproduction, with some species undertaking long journeys to specific breeding or pupping grounds. Covering immense distances allows these sharks to exploit dispersed food sources and complete their life cycles where resources can be spread thinly.
Deep-Sea Dwellers
Beyond the sunlit surface, the deeper layers of the open ocean host unique shark species adapted to extreme conditions of pressure, cold, and darkness. These deep-sea dwellers inhabit the mesopelagic, bathypelagic, and even deeper zones, where sunlight does not penetrate and food is scarce. Their adaptations include slower metabolisms to conserve energy, large eyes to capture what little light exists, or enhanced sensory organs to detect prey in the dark.
The frilled shark, often described as a “living fossil,” has an eel-like body and multiple rows of sharp, three-pronged teeth, using them to lunge at prey like squid and fish in depths between 500 and 1,000 meters.
Another deep-sea shark is the goblin shark, characterized by its long, protruding snout and extendable jaws. This species lives in benthopelagic zones near the ocean bottom, using its specialized snout to detect prey in complete darkness.
The Greenland shark, found in the cold, deep waters of the North Atlantic and Arctic Oceans, is notable for its incredibly long lifespan, potentially living for centuries. These deep-sea sharks represent a unique part of the ocean’s shark diversity, thriving in environments far removed from human observation.