Sharks & rays

They have broad, flat gills and look like tiny plates lined up on the sides of their bodies, which inspired their class name (Elasmobranchii = plate gills).

Elasmobranchs are special because of their unique features: experts in osmoregulation (a unique adaptation to regulate and balance their body internal fluids with the water around them), temperature regulation, and heightened sensory systems, including electrical field detection.

They don’t have bones like other fish; instead, they have skeletons made of a particular type of cartilage. They also have tiny, tooth-like dermal placoid scales for protection and more effortless movement through the water. Their teeth are constantly replaced, so they always have sharp ones ready for catching prey. Many elasmobranch species give birth to live offspring.

They hold a significant place in the evolutionary history of jawed vertebrates, with fossils tracing back nearly 400 million years. In ecosystems, they are essential apex predators, but today also vulnerable to fishing pressure. Their population is smaller than those lower in the food chain.

Slow growth, long lifespan, and late maturity, combined with low reproductive capacity, hinder population recoveries from depletion. Removing these apex predators can have negative environmental impacts.

The cartilaginous skeleton comprises a dense network of fibres and cells, giving it strength and resilience. It is a flexible and lightweight tissue that provides structural support to bodies. It helps sharks and rays swim efficiently, as the absence of heavy bones reduces their overall weight, making them more buoyant.