Most fish do in fact sleep. All fish except for sharks do not have eyelids therefore they do not close their eyes like humans do. Some find a crevice to hole up in or lie on the bottom motionless in a sort of meditative state of relaxation while still being aware of any danger that may be around.
Fish can drown. Fish do not actually breathe water. Instead, they filter dissolved oxygen from it. They need a constant flow of oxygen flowing through their gills to keep from drowning.
Cuttlefish, starfish and jellyfish are not technically fish. Generally-speaking, fishes must have
skulls, gills, and fins. Surprisingly, not all fishes have proper spines.
Some fish including tuna, swordfish, and some shark species have the ability to keep their core body temperature higher than their surroundings.
Eels can breathe air directly through their skin. Electric eels can generate up to 600 volts which is 50 times more than a car battery.
Daytime fishes have better vision than we do, able to see ultraviolet light normally invisible to human beings. Night Time fishes have less developed eyesight, but see better in the dark than we do.
Fish have superior hearing; they communicate with grunts and other sounds and have the ability to hear sounds with their ears and pick up the vibrations of sounds in the with their skeletons. It is believed sharks can hear sounds from several miles away.
Schools of fish have a single leader that stays in the middle of the school. The fish around it follow its direction, swimming in any direction the leading fish decides to swim in.
Some fish have the abilty to change sex in order to carry out its functions to the group.
The Biblical tale of Jonah originally involved a fish. Only modern translations describe it as a whale. In older texts, it’s only said that a big fish swallowed him up. After 3 days, the fish vomited him out so he could continue on his divine mission to Nineveh.
Mankind has only thoroughly explored 1% of the ocean.
The deepest part of the ocean in the world is in the western pacific ocean off the coasts of Taiwan and the Philippines called the Mariana trench. It is roughly 7 miles deep. If Mount Everest were placed inside the trench it would still be underwater by 1.2 miles.
Some fish are smarter than others and can experience both positive and negative emotions. They have memories and can use tools. They have even been known to remember musical tunes.
There are over 30,000 known species of fish with many others yet to be discovered.
Saltwater fish need to drink water directing water intake into their digestive tract. Freshwater fish do not need to drink water.
There are more species of fish than mammals, birds, reptiles and amphibians put together.
