A DIVERSE GROUP OF FISH
Worldwide there are over 500 species of shark, 600 skates and rays and 50 chimaera. All unique and amazing in their own ways, and perfectly adapted to the environment in which they live! You can find them in almost every marine ecosystem on earth. Including freshwater!
Sharks have adapted to inhabit a wide range of niches in every ocean and sea around the world. From the Portuguese Dogfish that lives in total darkness at depths up to 3,700m. To the Greenland Shark that tolerates the icy waters of the Arctic. The Blue Shark which can migrate over 5,700 miles. And the Bull Shark which can be found in freshwater up to 1,860 miles from the sea!
Many, but not all, shark species occupy the highest trophic level in a food web. These apex predators play a particularly important role in maintaining the diversity, function and health of an ecosystem. They impact directly through predation on meso-predators (middle level consumers) and indirectly through their interactions with other members of the ecosystem.
Their removal can have complex and unpredictable ecological consequences. Something researchers are only just beginning to understand.
SKATES & RAYS
Skates and rays are very closely related to sharks. They’re flatter in shape, which makes them well suited for life on the sea-floor. Their mouth, nostrils and gills are located on the underside of their body. While their eyes are on top.
Skates and rays spend a lot of time buried in the sand. Either hiding from predators or lying in wait for unsuspecting prey. With their gills and nostrils buried in sand you may be wondering how they breathe? All sharks have two small breathing holes found near the eyes. These are known as spiracles. When buried, skates and rays rely on these to provide them with oxygen.
There are over 600 species of skate and ray worldwide. There’s the graceful Manta Ray, the largest ray in the world reaching up to 9m. Electric rays that can deliver a powerful shock. And the rostrum wielding sawfish, which uses its saw-like snout to stun its prey.
400 MILLION YEARS OF EVOLUTION
Sharks and their relatives have lived in our oceans for over 400 million years. Well before even the dinosaurs roamed the earth
It’s thought that sharks and their relatives descended from a small leaf-shaped fish that had no eyes, fins or bones. These fish then evolved into the 2 main groups of fish seen today. Bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes – the sharks, skates, rays and chimaera).
The fossil record documents over 3,000 shark species. Yet it’s likely many more existed but disappeared without trace. After death, a shark’s skeleton rots away due to it being made of cartilage instead of bone. So, usually the only remains they leave behind are their teeth, dermal denticles and fin spines. But we can tell a lot from a single tooth. From this, scientists can tell what the shark fed on and even identify the species it belonged to.