1. Seahorses are the only fish that swim upright.
2. Most fish have little salt in them. Sharks, however, have meat as salty as the ocean they live in.
3. The oldest fishhook ever found dates back to about 42,000 years ago.
4. Starfish are not fish. Neither are jellyfish.
5. Most fish cannot swim backwards. Those that can are mainly members of one of the eel families.
6. Although the fangtooth fish is only a few inches long, it has teeth about the size of a human’s.
7. A fish does not add new scales as it grows, but the scales it has increase in size. In this way, growth rings are formed and the rings reveal the age of a fish.
8. Most brands of lipstick contain fish scales.
9. A fish can drown in water. Like humans, fish need oxygen, so if there isn’t enough oxygen in the water, they will suffocate
10. Fish would suffocate if they tried to chew because chewing would interfere with water passing over their gills.
11. The most poisonous fish in the world is the stone fish. Its sting can cause shock, paralysis, and even death if not treated within a few hours.
12. Unlike most other fish, the ocean sunfish does not have a tail. A female sunfish can lay 300 million eggs each year. Each egg is smaller than the period at the end of this sentence.
13. The term “fish” is used when referring to one species of fish (e.g., 10 salmon are 10 fish). The term “fishes” is used when referring to more than one species (e.g., 10 salmon, 3 trout, and 1 angel fish are 14 fishes).
14. A seahorse can move each of its eyes separately. One eye can look forward while the other looks backward. Seahorses can also change their colour to match their surroundings.
15. Catfish have over 27,000 taste buds. Humans have around 7,000.
16. Some fish do not have scales. Sharks, for example, have rough sandpapery skin instead of scales.
17. In Japan the puffer fish is a succulent but lethal delicacy. It contains tetrodotoxin, a deadly poison. However, it is so delicious that Japanese gourmets risk their lives to prepare it. To make this high-risk dish, chefs must have a certificate from a special school that teaches preparation of this toxic fish.
18. The mudskipper is a fish that spends most of its time out of water and can “walk” on its fins. It carries a portable water supply in its gill chambers when it leaves the water. It can also breathe through the pores of its wet skin.
19. The biggest fish in the world is the giant whale shark, which can grow to nearly 60 feet, or the length of two school buses. It weighs over 25 tons and eats mainly plankton. It has over 4,000 teeth, though they are only 3 mm long.
20. Humans have been amazed for centuries that salmon, after journeying across the ocean, can find the river where they were born. In the Yukon River in Alaska and in Canada, certain tagged Chinook salmon covered nearly 2,000 miles in 60 days. Salmon also have adapted to live in a variety of aquatic environments, including rivers, lakes, estuaries, coral reefs, and the open sea.