10 Facts You Never Knew About Fish

1. Most fish don’t have eyelids, but they do go to sleep. They have periods of rest that save energy and serve as a restorative function. Some fish are still aware of dangers, and others, like the Spanish Hogfish can be lifted all the way to the surface. Others, like sharks and tunas, have to keep moving to breathe, so they cannot sleep.

2. Atlantic Mollies exhibit homosexual behaviour to attract females.

3. A fish’s name is important in its marketing. The goosefish is a toad-coloured fish with a huge mouth. When someone decided that it was quite tasty, they renamed it monkfish and it became wildly popular, particularly in the 90s.

Image: Blueyou.com

4. Clownfish are hermaphrodites, and their sex is determined by their social situation.

5. Cartilaginous fish such as sharks and rays have ampullae of Lorenzini, which are little black dots in the pores of their skin. They help the fish sense electric fields in water, such as that which is found in the muscle contractions of animals, which makes finding food easier.

6. A sailfish can travel at 110km per hour.

7. Coelacanths were supposed to have become extinct in the Cretaceous period with the dinosaurs. However, in 1938, a live one was caught off the coast of South Africa, and since then, others have been found. They can grow up to two metres long, and they feed on smaller fish (including sharks!).

Image: Mark V. Erdmann

8. Fish have been known to be displaced from lakes and the ocean by hurricanes and storms inland, killing hundreds of fish. 

9. The Swedish navy had picked up strange noises that they were worried might be Russian submarines. Their scientists discovered that it was in actual fact herrings, which communicate through farts!

10. Goldfish can see more colours than humans, including ultra-violet and infra-red light. This is why they don’t like to be kept in the dark.