Are Sharks Fish?

Sharks are older than trees and they have existed for more than 400 million years, which also makes them older than the dinosaurs. They swim in the ocean, strike fear in the hearts of many, and they’re much different than the fish in your aquarium at home. Sharks eat fish, but are sharks fish?

Quite a few sharks are apex predators in the ecosystem that they inhabit. There are over 500 different kinds of sharks, and they vary in size from tiny to gigantic. Their appearance, habits, and habitat also vary widely, though there are some distinct commonalities.

Fish are teleosts and sharks are elasmobranchs. What do these big words mean? Again we ask, are sharks fish?

We’ll define what a fish is, discuss if a shark fits the definition, and then discuss some interesting details about sharks.

What is a Fish?

Fish are vertebrates that solely live in water and have gills. They have no limbs with digits on them. Digits are things like fingers and toes.

Out of all of the species with backbones, fish make up about 50% of the total. This comparison includes mammals like humans, reptiles, birds, and amphibians. They are the most diverse animals with backbones in the world and it’s believed there are many more to be discovered.

Fish live in water and get the oxygen they need through their gills. These gills look like slits on both sides of their head. Water passes over these gills, which gives them a continuous flow of oxygen.

Fish live in any kind of aquatic environment, from freshwater to the salty depths of the ocean. Most fish have bony skeletons which make them teleosts. Out of all of the fish alive today, about 96% are bony fish. They are usually fusiform, which means torpedo-shaped, though this isn’t always true.

All fish are cold-blooded, which means that the environmental temperature is their internal body temperature. They have fins that they use to move around their aquatic environments.

Are Sharks Fish?

So, are sharks fish? Yes, sharks are fish. However, not all fish are sharks. Both sharks and fish use gills to obtain oxygen from the water around them, and they live fully in water their entire lives. Sharks have five gill slits that they use to breathe, while almost all other fish have one.

Sharks are a special type of fish called elasmobranchs. Skates, rays, and sawfish are also elasmobranchs, but they are not sharks. Some fish can live in freshwater environments, while only a select few sharks can tolerate freshwater.

Unlike teleosts, elasmobranchs have skeletons made up entirely of cartilage and connective tissue. There is no bone. Sharks also have pupils that contract and dilate while teleost fish do not.

Sharks are also a bit different than teleosts in how they reproduce. A bony fish’s strategy for reproduction is to produce a lot of young that are barely developed, whereas sharks have few young that are almost fully developed. Both contain species that lay eggs.

Sharks are almost exclusively carnivorous, while different kinds of fish eat a vast variety of things, including plants.

Bony fish can move their pectoral, or front, fins in different directions. This allows them to go backward. Sharks have pectoral fins that do not move, which makes them unable to swim backward.

What is a Shark?

A shark is a fish that does not have bones. Sharks have their entire skeleton made up of cartilage.

Some think sharks are related to mammals because a few species perform live births. However, a shark has much shorter intestines than mammals and their digestive systems are almost completely different. They also don’t produce milk, don’t have lungs, nor do they have hair.

Sharks have adaptations that keep them from being too vulnerable without bones. They have what are called dermal denticles. These denticles are shaped like teeth and are also covered in enamel. They’re on the outside of their skins like scales. Unlike fish scales, denticles don’t grow along with the fish. Rather, new ones are formed as the shark grows. Fish scales grow with the fish.

Dermal denticles are armor against predators. Sometimes, they aid in streamlining the swimming process so a shark can go faster.

Sharks also lack swim bladders that most other fish have. A substance in their liver oil and their cartilaginous skeleton plays the same role in keeping them afloat. Cartilage is about half as heavy as bone, and oil is buoyant.

While all fish have gills, shark gills don’t have a cover over the slits like other fish. That’s why they’re easy to spot on the side of a shark but are inconspicuous on a lot of fish.

Do Humans Eat Sharks?

Yes, humans eat sharks. It is legal to consume it in the United States. However, shark meat isn’t immensely popular in America because it contains high levels of mercury.  

Sharks that frequent human menus are threshers, porbeagles, blacktip, dogfish, gummy sharks, and shortfin mako sharks. Shark meat is usually marinated to reduce the sharp urea flavor that is present in the flesh. It’s also commonly salted, dried, pickled, or smoked.

Asia eats half of the sharks that are fished in the world. Italy is the largest importer of shark meat, followed by France. Shark meat is immensely popular in Japan, and it can be found readily in supermarkets.

It is common in certain parts of the world, and it is prepared in various ways. You can’t eat shark liver as the number of vitamins and minerals are toxic to humans. Not all kinds of sharks are eaten – as some sharks, with threatened populations, are protected in a lot of places.

It seems distasteful to some that sharks are consumed, but that is rooted in the anger we have for the shark fin industry. Sharks that are regularly on the menu in certain places are harvested sustainably and as a local food source. They have nothing to do with needlessly slaughtering massive amounts of sharks just for their fins.

The photo featured at the top of this post is © Greg Amptman/Shutterstock.com