Fish that have thin fins with a split tail indicate that they move very quickly or may need them to cover great distances. On the other had, fish that live among rocks and reefs near the ocean floor have broad lateral fin and large tails.
Fish have sleep-like periods where they have lowered response to stimuli, slowed physical activity, and reduced metabolism but they do not share the same changes in brain waves as humans do when they sleep.
A fish can drown in water. Like humans, fish need oxygen, so if there isn’t enough oxygen in the water, they will suffocate.
Since a fish’s jaw is not attached to its skull, many fishes can shoot their mouths forward like a spring to catch startled prey.
Fish would suffocate if they tried to chew because chewing would interfere with water passing over their gills.
Sharks are the only fish that have eyelids.
A ship has a heavy keel in the lower part to keep it from capsizing. Fish, on the other hand, have the keel on top. If the paired fins stop functioning to keep the fish balanced, the fish turns over because its heaviest part tends to sink, which happens when it dies.
Some fish, such as the herbivorous fish (grazers), often lack jaw teeth but have tooth-like grinding mills in their throats called pharyngeal teeth.
Electric eels and electric rays have enough electricity to kill a horse.
On average, flying fish can glide 160 feet (50m), but have been known to glide as far as 660 feet (200 m). And they can reach heights up to 19 feet (6m).
Most fish have taste buds all over their body.
Although the fangtooth fish is only a few inches long, it has teeth about the size of a human’s.
An inflated porcupine fish can reach a diameter of up to 35 inches (90 cm). It puffs up by swallowing water and then storing it in its stomach. The stomach increases in size with more water. If the fish is taken out of water, it can inflate in a similar way by swallowing air.
Lungfish can live out of water for several years. It secretes a mucus cocoon and burrows itself under the unbaked earth. It takes in air with its lung through a built-in breathing tube that leads to the surface. A lungfish has both gills and a lung.
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.
Some fish, such as the great white shark, can raise their body temperature. This helps them hunt for prey in cold water.
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.
The word “piranha” is from the Tupi (Brazil) pira nya and means “scissors.” Found in freshwater rivers in South America, piranhas have razor-sharp teeth. They typically eat fish, insects, seeds, fruit, and even larger animals such as horses. While there are no proven reports of piranhas killing a person, they do eat human carcasses.
Most fish reproduce by laying eggs, though some fish, such as great white sharks, give birth to live babies called pups.
The fastest fish is the sailfish. It can swim as fast as a car travels on the highway.
The oldest known age for a fish was an Australian lungfish. In 2003, it was still alive and well at 65 years old.
Seahorses are the only fish that swim upright.
An estimated one third of male fish in British waters are changing sex due to pollution in human sewage.
The slowest fish is a seahorse. It swims so slowly that a person can barely tell it is moving. The slowest is the Dwarf Seahorse, which takes about one hour to travel five feet. It even looks like it is simply standing up, not swimming.
Saltwater fish need to drink more water than freshwater fish. Since seawater is saltier than the liquids in a fish’s body, water inside the fish is constantly flowing out. If they didn’t drink to replace the lost water, saltwater fish would dry up like prunes.
Some fish do not have scales. Sharks, for example, have rough sandpapery skin instead of scales.
Fish use a variety of low-pitched sounds to convey messages to each other. They moan, grunt, croak, boom, hiss, whistle, creak, shriek, and wail. They rattle their bones and gnash their teeth. However, fish do not have vocal chords. They use other parts of their bodies to make noises, such as vibrating muscles against their swim bladder.
In Japan, the fugu, or 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.
The oldest fishhook ever found dates back to about 42,000 years ago.
The word "halibut" means "holy flatfish" (hali=holy + butte=flatfish) because it was only eaten on holy days.
Hammerhead sharks can live in schools of more than 500 sharks. The strongest female swims in the middle. When she is ready to mate, she shakes her head from side to side to signal the other female sharks to move away so she is the center of attention.