Parrotfish make themselves a kind of mucus 'sleeping bag' which masks their smell from predators and keeps parasites away.
4
The seahorse is the only fish to have a neck.
12
Sharks, like other fish, have their reproductive organs in their chests.
248
Cymothoa exigua is a type of parasite that enters through fish's gills, eats their tongue, and then replaces it.
6
Urechis unicinctus is a species of marine spoon worm that is widely referred to as the ‘penis fish’.
2
On some poorly researched trivia lists it is stated as a fact that a pregnant goldfish is called a twit. This is not true as goldfish lay eggs.
71
A koi fish, named "Hanako", was owned by several individuals over many years and lived to be 226 years old, dying in 1977.
6