Understanding Cartilaginous Fish: The Difference Between Sharks and Rays

Both sharks and rays are cartilaginous fish, meaning they have skeletons made completely out of cartilage. They are also closely related, sharing a common prehistoric ancestor. They are so similar that some varieties of sharks are often mistaken as rays. However, they are very different biologically and are considered two separate species of animal. So why are they considered so different if they are the only animals on the planet to have cartilaginous skeletons? What makes these two related animals separate species? Here are some of the primary differences between sharks and rays:

A Case Of Mistaken Identity

There are over 440 different sharks of the world and they all have very unique physical characteristics. Some of these sharks have physical traits that make many people mistake them for a species of ray. Bottom-dwelling sharks like Angel Sharks, Carpet Sharks, and Wobbegongs all have long flat bodies and wide pectoral fins, so people often mistake these sharks for rays. On the flip side, there have also been cases where a school of rays have been reported as a school of sharks. One such report was in 2005 when beachgoers thought a group of clam-eating rays were sharks engaging in a feeding frenzy off the coast of Staten Island in New York. These reports are surprisingly common for such different looking species.

Differences In Appearance Between Sharks And Rays

Though some sharks have long, flatter bodies, the bodies of rays are really flattened. They have disc-like, circular shaped bodies with very large connected pectoral fins. Rays also have long skinny tails at the ends of their bodies and tend to be much smaller than most sharks. Depending on the species, rays range in size from 10 in (25 cm) to 7 ft (2 m). They also have no anal fins but they always have spiracles on the top of their heads. Sharks on the other hand, even with flatter bodies tend to be more elongated and slender. They also have much smaller pectoral fins that are very distinct from their body. Some species of sharks have anal fins and others do not have spiracles. Sharks also have caudal fins on their tails which tend to be long and bulkier. So there are some obvious differences in appearance.

Shark And Rays Breath Differently

Though both sharks and rays use gill slits to breath underwater, they tend to breath differently. First of all rays have gill slits on the underneath side of their bodies, while sharks tend to have gill slits on the sides of their heads. Rays breathe by sucking in water through their spiracles and exhale it over their gills. Sharks on the other hand breath in two ways depending on the species. They either ram breath which means they swim through the water passing it over their gills or they pull in water through their mouths and over their gills. So sharks tend to be more active swimmers in order to breath, while rays can sit still for long periods.

Sharks And Rays Swim Differently

Another big difference between sharks and rays is how they swim. Rays swim two different ways depending on the species. Some rays flap their pectoral fins like wings to help propel them both forward and laterally. Other rays will wiggle their bodies in a wave-like motion to propel themselves. They then use their tails to help them steer and maintain balance. Sharks on the other hand use their tails to swim. The propel themselves by swinging their tails back and forth and then steering their movements with their pectoral fins. Rays also swim more slowly than sharks, usually around 9 mph (14.5 kph) with top speeds of 22 mph (35.4 kph). Sharks on the other hand swim very fast. Most sharks can swim up to 25 mph (40 kph), while the fastest sharks on the planet, Mako Sharks, can swim at an impressive 60 mph (96.6 kph).

Sharks And Rays Hunt Differently

Rays tend to eat shellfish, crustaceans, and mollusks. So they usually only hunt along the bottom of the seafloor. They have adapted teeth specifically for crushing the shells and exoskeletons of their prey. Their teeth are sturdy and round. Some species of ray feed on zooplankton so they filter feed. Rays also tend to hunt in cooperative groups. Sharks on the other hand eat a whole variety of ocean animals depending on the species. They have sharp teeth in multiple rows are more aggressive hunters. They hunt along the seafloor, in open water, and along the coast lines. They also rarely hunt in groups except during mating season.

Rays And Sharks Have Different Defensive Mechanisms

Sharks, especially larger sharks like Great White Sharks, Bull Sharks, and Whale Sharks, are apex predators and don’t have any natural predators beyond mankind. However, many sharks, fish, and whales feast on rays, so they have developed different defensive strategies. Some rays have poisoned barbs on their tails, while others can emit electric shocks when attacked. They also bury themselves in the sand and mud to hide from predators. Sharks on the other hand don’t have as many evolutionary adaptations to protect them from predators. Sharks that are vulnerable to predation are usually smaller and may only have a dorsal spine or camouflaged skin to protect themselves. So unlike rays, sharks are designed more to be effective hunters than to protect themselves from predators.

As you can see there are many physical and behavioral differences between rays and the sharks of the world. Though they are closely related and often mistaken for one another, they are extremely different species. Rays and sharks look differently, swim and hunt differently, and are at different points in the ocean food chain. So even though they share a similar ancestry and skeletal makeup, they are very different animals.