Fish Trivia
0Loading crowd target
0Loading crowd target
7correct to beat the crowd
96 free Fish trivia questions with answers — nature quiz, new questions added Oct 2026.
43 free fish trivia questions with answers. This fish trivia quiz swims from the basics (how many species there are, what a swim bladder does, which fish is the largest) to the genuinely odd: the fish with a transparent head, the shark that may live five centuries, the eel that shocks at 860 volts, and the male seahorse that gives birth. It covers sharks and rays, freshwater giants like the arapaima and wels catfish, aquarium favourites such as goldfish, bettas and koi, food fish like salmon, cod and bluefin tuna, and the deep-sea anglerfish whose males fuse to their mates. Easy questions suit kids and family quiz nights; the later ones will stretch marine-biology fans. Every answer was checked against encyclopaedia entries before publishing, and each question carries the sentence that supports it.
30 of 96 questions with answers and explanations. Play the quiz
Q 01Roughly how many living fish species are known to science?
About 33,000
About 33,000 species are known, and land animals with backbones, humans included, are really an offshoot of fish that moved onto land.
Q 02What is the largest living species of fish?
Whale shark
The whale shark, the biggest fish alive, lives on some of the smallest food, filtering plankton and small fish out of the water it gulps.
Q 03Which geological period is nicknamed the 'Age of Fishes'?
Devonian
The Devonian ended in mass extinctions, and the armoured placoderms that had dominated its waters all but vanished with it.
Q 04Which internal organ lets many bony fish adjust their buoyancy?
The swim bladder
The swim bladder is a gas-filled sac: by adding or releasing gas, a fish can hold its depth without having to keep swimming.
Q 05What is the sensory system that lets fish detect water currents and vibrations called?
The lateral line
The lateral line is a row of pressure-sensing organs, and the blind Mexican cave fish, with no working eyes, relies heavily on it to find its way.
Q 06The coelacanth was thought long extinct until a live one was caught off which country in 1938?
South Africa
In South Africa, museum curator Marjorie Courtenay-Latimer spotted it in a local fisherman's catch, and the genus Latimeria is named after her.
Q 07In which fish does the male carry the fertilised eggs in a brood pouch and give birth?
Seahorse
Seahorse fathers slowly change the fluid in the brood pouch from body fluid to seawater as the young develop, readying them for life in the sea.
Q 08When the dominant female in a clownfish group dies, what happens?
The breeding male changes sex
The breeding male changes sex and takes her place, and the largest non-breeder then becomes the new breeding male.
Q 09Up to how many volts can the most powerful electric eel species deliver?
About 860
About 860 volts came from Volta's electric eel, described in 2019; despite the name, electric eels are knifefish, closer to catfish than to true eels.
Q 10Which toxin makes pufferfish (fugu) potentially deadly to eat?
Tetrodotoxin
Tetrodotoxin is believed to come from bacteria in the pufferfish's food, and in Japan only specially trained, licensed chefs may prepare fugu.
Q 11Salmon that hatch in rivers, mature at sea and return to spawn are called what?
Anadromous
Anadromous salmon head back to the very stream where they hatched, finding it largely by smell, since its chemistry is imprinted on them when young.
Q 12Goldfish were first selectively bred for colour more than 1,000 years ago in which country?
China
China had domesticated goldfish by the Song dynasty, and pet goldfish released into the wild elsewhere have since become invasive pests.
Q 13In a 1994 study, goldfish whose food lever paid out only on a schedule learned to press it when?
Same time each day
Same time each day: the lever fed them for an hour daily, and they learned to anticipate it even under constant light, a sign of an internal clock.
Q 21Which shark can live in fresh water and has been found far up the Amazon River?
Bull shark
Bull sharks can live in fresh water, and haunting shallow waters close to people may make them the most dangerous shark to humans.
Q 22Caviar is traditionally the processed roe of which fish?
Sturgeon
Sturgeon caviar was relatively cheap and common until sturgeon stocks began to collapse in the late 19th century, turning it into a luxury.
Q 23The giant oarfish, the longest bony fish, may lie behind old sightings of what?
Sea serpents
Sea serpents: oarfish are ribbon-like and very long, and they drift near the surface or wash ashore when sick or dying, which may explain the legends.
Q 14Which fish is the villain of Peter Benchley's 1974 novel Jaws?
Great white shark
A great white shark terrorises the town in Jaws, and Benchley later expressed regret for writing about sharks in a way that fed fear of them.
Q 15Which fish can spend long periods out of water on tidal flats, breathing through its skin and mouth lining?
Mudskipper
Mudskippers also carry a bubble of air in their enlarged gill chambers, which keeps them breathing while they feed and court on land.
Q 16Which Caribbean country is known as 'the land of the flying fish' and puts it in its national dish?
Barbados
Barbados's flying fish don't really fly: they build up speed underwater, burst through the surface and glide on their outspread fins.
Q 17In deep-sea anglerfish, what did scientists first mistake the tiny males for?
Parasites attached to the female
The 'parasites attached to the female' were males that bite on, fuse with her skin and share her bloodstream, depending on her for food from then on.
Q 18Which fish produces more eggs at a time than any other known vertebrate, up to 300 million?
Ocean sunfish
The ocean sunfish is thought to be named for basking at the surface, which may help it warm up after deep, cold dives.
Q 19Which US president helped cement the piranha's fearsome reputation after a 1913 trip to Brazil?
Theodore Roosevelt
He described them as vicious creatures in his 1914 book Through the Brazilian Wilderness.
Q 20Which fish, once estimated at 125 km/h, is often cited as the fastest in the ocean?
Sailfish
Sailfish lost much of that record in a 2016 muscle study, which found such speeds unlikely and estimated a top speed of only about 30 km/h.
Q 24The betta, a popular aquarium fish, is the national aquatic animal of which country?
Thailand
Thailand has long bred bettas for fighting, and its government named the fish a national animal in 2019, citing its historical and cultural significance.
Q 25Koi are often mistaken for oversized goldfish, but they are coloured varieties of which fish?
Carp
Carp farmers in Niigata's snowy mountains kept the fish as winter food, and from the early 19th century they bred the colourful ones for show.
Q 26A remora clings to sharks and whales using a suction disc that evolved from which body part?
Its first dorsal fin
Its first dorsal fin evolved into the ridged sucking disc, and a riding remora is thought to feed on scraps from its host's meals.
Q 27Which English king is said to have died from eating 'a surfeit of lampreys'?
Henry I
Henry I's death in 1135 was long blamed on the lampreys, but historians doubt it, and a 2023 medical review proposed a Listeria infection instead.
Q 28Which fish has one of the largest brains for its body size and may recognise itself in a mirror?
Manta ray
Manta rays also visit reef cleaning stations, holding still for minutes while small fish pick off their parasites, and many return to the same station.
Q 29What is generally regarded as the most venomous fish in the world?
Stonefish
Stonefish are camouflaged so well as rocks or coral that people rarely see them, and the venomous spines on their backs can deliver fatal stings.
Q 30Which shark, thought to live for several centuries, has the longest known lifespan of any vertebrate?
Greenland shark
Greenland sharks were aged by radiocarbon-dating the lenses of their eyes, which suggested females take about 150 years to reach maturity.