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50 free Fish trivia questions with answers — nature quiz, new questions added Aug 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 50 questions with answers and explanations. Play the quiz
Q 01Roughly how many living fish species are there, more than all other vertebrates combined?
About 33,000
About 96% of them are teleosts, the ray-finned group that can protrude its jaws.
Q 02What is the largest living species of fish?
Whale shark
Despite its size it is a filter feeder that eats plankton, krill and small schooling fish; the largest reliably measured individual was 18.8 metres long.
Q 03Which geological period is nicknamed the 'Age of Fishes'?
Devonian
Placoderms, lobe-finned fish and early sharks all diversified then, roughly 420 to 360 million years ago.
Q 04Which internal organ lets many bony fish adjust their buoyancy?
The swim bladder
Lungs in land animals are homologous with it; some fish can even detect sound through it.
Q 05What is the sensory system along a fish's flanks that detects currents and vibrations called?
The lateral line
Blind cave fish navigate almost entirely by it.
Q 06The coelacanth was thought long extinct until a live one was caught off which country in 1938?
South Africa
It is the classic Lazarus taxon; a second species was later found in Indonesian waters.
Q 07In which fish does the male carry the fertilised eggs in a brood pouch and give birth?
Seahorse
The female can deposit up to 1,500 eggs, and the male carries them for 9 to 45 days.
Q 08When the dominant female in a clownfish group dies, what happens?
The breeding male changes sex
Clownfish live in a size-based hierarchy with the female on top; everyone else moves up one rung.
Q 09Up to how many volts can an electric eel deliver?
About 860
Despite the name it is a knifefish, not a true eel, and it uses three separate electric organs.
Q 10Which toxin makes pufferfish (fugu) potentially deadly to eat?
Tetrodotoxin
Bacteria in the fish's gut are now thought to be the source; only specially trained chefs may prepare fugu in Japan.
Q 11Salmon that hatch in rivers, mature at sea and return to spawn are called what?
Anadromous
They return primarily to their natal streams; young 'parr' spend six months to three years there before becoming silvery 'smolts'.
Q 12Goldfish were first selectively bred for colour more than 1,000 years ago in which country?
China
Red and orange mutations of grey carp were first recorded during the Jin dynasty; the fish reached Japan centuries later.
Q 13How long is a goldfish's memory span, contrary to the popular myth?
At least three months
They can also tell apart different shapes, colours and sounds.
Q 21Which fish, once estimated at 125 km/h, is widely considered the fastest in the ocean?
Sailfish
Research in 2015 and 2016 cut the estimate to a still-brisk 35 to 55 km/h.
Q 22Paedocypris progenetica, one of the smallest known fish, has an average length of roughly what?
1.1 cm
It lives in Indonesian peat swamps and weighs between 4 and 16 milligrams.
Q 23Caviar is traditionally the processed roe of which fish?
Sturgeon
In the 19th century the United States controlled about 90% of the world caviar trade.
Q 24The largest one on record, a 7.2-metre beluga, was caught in 1827 in the delta of which river?
Q 14Which fish is the villain of Peter Benchley's 1974 novel Jaws?
Great white shark
Its triangular teeth reach 7.5 cm, and its jaws are connected to the skull only by muscle and tendon so they can thrust forward.
Q 15Which fish can spend long periods out of water on mudflats, breathing through its skin and mouth lining?
Mudskipper
They defend territories and court partners on land, and keep an air pocket in their burrows when the tide comes in.
Q 16Which Caribbean country is known as 'the land of the flying fish' and puts it in its national dish?
Barbados
The national dish is cou-cou and flying fish.
Q 17In deep-sea anglerfish, what did scientists first mistake the tiny males for?
Parasites attached to the female
The male fuses to the female's body; an unusual immune system is what allows the two to merge.
Q 18Which fish produces more eggs at a time than any other known vertebrate, up to 300 million?
Ocean sunfish
Genetic analysis found the sunfish is a generalist predator: jellyfish make up only around 15% of its diet.
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 20How does the archerfish catch insects sitting on leaves above the surface?
It shoots them down with jets of water
They can knock down prey up to 3 metres above the surface, aiming at angles between 45 and 110 degrees.
Volga
It weighed 1,571 kg; sturgeon lineages go back to the Early Jurassic.
Q 25The Siamese fighting fish, or betta, is the national aquatic animal of which country?
Thailand
Its labyrinth organ lets it gulp air at the surface, which is why it survives in tiny bowls.
Q 26Ornamental koi breeding began in the early 19th century in which Japanese region?
Niigata
The Japanese word nishikigoi means 'brocaded carp'.
Q 27A remora clings to sharks and whales using a suction disc that evolved from which body part?
Its first dorsal fin
Sliding backward increases the suction; swimming forward releases it.
Q 28Which English king is said to have died from eating 'a surfeit of lampreys'?
Henry I
Lampreys are jawless fish, more closely related to hagfish than to any jawed vertebrate.
Q 29Which fish has the largest brain of any fish and may recognise itself in a mirror?
Manta ray
The giant oceanic species reaches 7 metres across; their brains even have heat-conserving networks of blood vessels.
Q 30What is generally regarded as the most venomous fish in the world?
Stonefish
Its stings can kill a human if untreated; the fish looks like an encrusted rock on the seabed.