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Which of the following features of a bony fish's body structure help it swim fast?
Leon is looking at Gilbert, his pet goldfish. He really likes fish and can’t wait to go scuba diving when the sea is warm enough! Whenever he goes scuba diving, it always surprises him how different fish can be from each other. Let’s take a closer look at some of them! Fish that are similar to Gilbert, like tuna and salmon, are called BONY fish.
These fish have bony skeletons and strong muscles that help them swim fast. Their bodies are spindle shaped or oval, and are covered in scales, and they have jaws. Bony fish also have a special organ, a swim bladder, that contains a mixture of gases. By changing the amount of gas in the bladder, a fish can move up or down in the water. But bony fish are just one group of fish!
Do you know that sharks, rays, and skates are types of fish too? These are CARTILAGINOUS fish. They have a skeleton made out of cartilage. Cartilaginous fish don’t have swim bladders, so they need to swim continuously. But like bony fish, cartilaginous fish also have jaws, and are covered in scales.
Bony fish and cartilaginous fish are very common, and share quite a few characteristics. But there is another, quite strange group of fish. JAWLESS fish. These get their name because they don’t have jaws! Fish in this group are hagfish and lampreys, and they are long and slim.
Hagfish look more like snakes than fish, because they don’t have any fins! They don’t have scales either, although their ancestors did. Also, they don’t have a full skeleton, but they do have something called a partial backbone. So if these three groups of fish are so different from each other, what is it that makes them all fish? They are all aquatic animals, and can’t survive without water.
They all have some kind of backbone, which makes them all vertebrates. They all breathe with gills, and they can’t regulate their body temperature themselves: they are cold-blooded. Fish are essential parts of healthy marine ecosystems, and they are also really important for humans - for many people who live near the water, fish are basic food. But overfishing and pollution have reduced the number of fish in our oceans by more than 80%. Leon is upset about that.
He’d do anything to protect Gilbert, and Gilbert’s close and distant relatives. Do you have any ideas about what we can do to protect fish?