Shark Fish: Real Sharks vs Aquarium 'Sharks' Explained

Yes, a shark is a fish. NOAA Fisheries puts it simply: sharks live in water and use their gills to take oxygen from it. What makes them different from most fish you catch or keep is the skeleton. Sharks have no bones; their skeleton is cartilage.

Wikipedia defines sharks as elasmobranch cartilaginous fishes with a ribless skeleton, skin covered in tooth-like dermal denticles instead of ordinary scales, five to seven gill slits on each side of the head, and pectoral fins that are not fused to the head. That last point separates sharks from rays, their closest relatives.

So the question 'is there a shark fish?' has two answers. Every shark is a fish. And several aquarium fish carry the word shark in their name without being sharks at all (see below).

Check the side of the head first. A real shark shows a row of five to seven separate gill slits on each side (Wikipedia). Ordinary bony fish, including every aquarium 'shark' below, have one gill cover on each side instead.

The three aquarium 'sharks' people ask about most:

• Rainbow shark, Epalzeorhynchos frenatum: a member of the carp and minnow family, Cyprinidae, from Southeast Asian rivers such as the Mekong and Chao Phraya. It grows to about 15 cm (6 in). Wikipedia describes it as strongly territorial, able to chase a smaller rival until it dies, and gives a minimum of 55 gallons with a 48-inch length for adults. The GloFish shop lists the fluorescent GloFish Rainbow Shark at about 2 to 3 inches for $14.99 (price checked 25 September 2026) and says it is best kept alone or in a tank large enough for separate territories
• Red-tailed, bala and black sharks: Wikipedia names these as related fish that should be kept apart from rainbow sharks to avoid fighting
• Iridescent shark, Pangasianodon hypophthalmus: a catfish, not a shark, from the Mekong and Chao Phraya. It reaches 130 cm (4.3 ft) and 44 kg in the wild, is sold as food under the names swai, basa and panga, and Wikipedia calls it a poor choice for home aquariums, where most specimens stay stunted at 15 to 30 cm

If you are not sure what you are looking at, photograph the fish side-on so the head and gill area are sharp; the FishLens app names the likely species.

Sharks cover a bigger size range than most people expect. Wikipedia gives the dwarf lanternshark at only about 17 cm (6.7 in) and the whale shark at roughly 12 to 18.8 m (40 to 62 ft), the largest fish alive.

Some live for centuries. A Greenland shark 5.02 m long was estimated at 392 plus or minus 120 years old, which means at least 272 years (Wikipedia).

They are also more fragile as populations than their reputation suggests. Wikipedia reports that shark populations have fallen by 71% since 1970, mostly from overfishing and finning.

Shark is eaten in many countries, but there are specific health cautions, and some groups are advised to avoid it.

• Mercury: the US Food and Drug Administration lists shark under 'Choices to Avoid: highest mercury levels' in its fish advice for people who are or might become pregnant, people who are breastfeeding, and children aged 1 to 11
• Liver: NOAA Fisheries says shark meat can be tasty and nutritious if properly prepared, but warns never to eat shark liver, because its vitamin concentrations can harm people
• Smell: Wikipedia notes that unprocessed shark meat develops a strong ammonia smell from urea as it breaks down

If you are unsure whether shark is right for you or your family, follow the FDA advice or ask your doctor. If you feel unwell after eating any fish, contact a doctor or your local poison control centre.

Shark is often sold under another name, which is why people search 'what is shark fish called'. Wikipedia lists:

• Flake in Australia, mostly gummy shark
• Rock salmon in British fish and chip shops, for small sharks
• Cação in Brazil, used for any species; Wikipedia names Brazil as the world's largest consumer of shark meat
• Dombaegi in Korea, salted shark meat

An Australian fish-and-chip label of 'flake' therefore does not tell you which shark species you are eating.

For great white sharks, the best-documented natural predator is the orca. National Geographic reports that in 1997 tourists near the Farallon Islands off San Francisco watched two orcas kill a great white and eat its liver, after which the whole local great white population, about a hundred animals, left the islands early. In 2017 five great whites washed up on South Africa's Western Cape with their livers removed through a neat tear between the pectoral fins; two orcas known as Port and Starboard were the suspected hunters. A great white liver can weigh up to 600 pounds, which is why orcas target it.

Measured by numbers killed, the answer is people: the 71% fall in shark populations since 1970 is attributed mainly to overfishing and finning (Wikipedia).