Interesting facts about fish


Fish are vertebrates (vertebrates have backbones) that live in water.

They are one of the six main groups of animals — along with invertebrates, amphibians, reptiles, birds and mammals.

The combination of gills, fins and the fact that they live only in the water make fish different from all other animals.


Fish are so abundant in the world’s oceans, lakes and rivers that new species are constantly being discovered.

There are over 30,000 known species of fish.

Fish come in many shapes and sizes.

The world’s largest fish is the whale shark, which can grow to 12 meters (40 feet) long and weigh an average of 19,000 kilograms (42,000 pounds).

whale shark


worlds smallest fish


greenland shark


koi fish

A tiny coral reef-dwelling fish called the pygmy goby (Eviota sigillatais the shortest-lived fish. The pygmy goby lives an average of 59 days, pipping the previous record holder, an African fish which lives for just over two-and-a-half months.

shortest lived fish pygmy goby


World’s deepest fishbelieved to be a snailfish – found in the western Pacific Ocean at a depth of 8,145 meters (26,722 feet).

The black marlin [photo below] is the fastest fish in the world – able to swim at a speed of 129 km/h (80 mph), followed by the sailfish at 110 km/h (68 mph).

black marlin

Fish diets vary by species. There are some carnivorous (meat eating) fish, some herbivorous (plant eating), and many omnivorous (both meat and plant eating) fish.

Freshwater fish do not actively drink water, but absorb the water through their skin and gills. On the other hand, saltwater fish do actively drink sea water. Their gills process the water and take out the salt.

Fish are cold-blooded with the exception of Tuna family, the Mackerel shark family and the opah or moonfish.

Fish can drown in water if there is not enough oxygen in the water. Fish require a consistent intake of oxygen to survive. Their gills absorb oxygen from water molecules as water passes through the gill membranes.

fish gills

In most fish respiration takes place through gills. Lungfish, however, possess one or two lungs. The labyrinth fish have developed a special organ that allows them to take advantage of the oxygen of the air, but is not a true lung.

Not all fish have scales. While scales are a characteristic of most fish, some fish, such as clingfish, lampreys and catfish, do not have scales.

fish scale


Some fish species can make audible sounds like clicks or croaks but most fish communicate with body language. Certain species will flare out their gill plates the same way a cat would raise the hair on their back.


school of fish


The primary means of fish reproduction are egg laying and live bearing. Egg-laying fish release eggs that are later fertilized. Live-bearing fish internally fertilize the female, who carries the offspring within until they develop and are birthed.

Some fish species are known to change sex during the course of their lives.

Some Fish, like the Triggerfish, can swim backward.

Seahorses are the only fish that regularly swim upright.


On average, flying fish can glide 50 meters (160 feet), but have been known to glide as far as 400 meters (1,300 feet). And they can reach heights up to 6 meters (20 feet).

Many types of aquatic animals commonly referred to as “fish” are not fish; examples include shellfish, cuttlefish, starfish, crayfish and jellyfish.

Fish do not have eyelids, with the exception of the shark.

Puffer fish are thought to be the world’s deadliest fish. Their poison is contained in their flesh and one puffer fish carries enough toxin to kill 30 people. Despite this, the meat of some species is considered a delicacy in Japan.

puffer fish

A robotic fish was accepted by other fish and became their leader during an experiment by New York University.



Fish feature prominently in art and literature, in movies such as Finding Nemo and books such as The Old Man and the Sea.

The fish is used often as a symbol by Christians to represent Jesus, or Christianity in general; the gospels also refer to “fishers of men” and feeding the multitude.


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