Could you spot the fish fake? Test your seafood fraud detective skills in our quiz

Nearly 40% of 9,000 products across 44 studies analysed by the Guardian were mislabelled. Photograph: The Guardian

1. 

   This is often sold as red snapper. What is it really?

   1. Trout

   2. Mahi mahi

   3. Tilapia

   4. Swordfish

2. 

   You order delicious grouper but what is this common substitute?

   1. Catfish

   2. Giant tiger prawn

   3. Cod

   4. Sea bass

3. 

   "White tuna" is frequently on the menu, yet does not actually exist. What is this fish that's used as a stand-in?

   1. Guppy

   2. Monkfish

   3. Spiny dogfish

   4. Butterfish

4. 

   This fish is often slipped on to plates as the prized bluefin tuna. What is it really?

   1. Mackerel

   2. Skipjack tuna

   3. Parrot fish

   4. Anchovy

5. 

   Hake is an increasingly popular fish prized for its flaky white flesh, but in shops and restaurants you might get fillets of this fish instead. What is it really?

   1. Hoki

   2. Barramundi

   3. Cuttlefish

   4. Dover sole

6. 

   Surely you're safe with cod – everyone knows what that tastes like, right? But studies show it's often swapped for this in fish and chips – what is it?

   1. Conger eel

   2. John Dory

   3. Pike

   4. Haddock

7. 

   And if you're in the US and you order haddock, what is this fish that could be hiding under your batter instead?

   1. Salmon

   2. Sprat

   3. American sole

   4. Whitebait

Solutions

1:C - Tilapia. Red snapper is an extremely popular reef fish that has been overfished to the point that stocks are now extremely low in most of its habitats. Its cheaper common substitute is tilapia, 2:A - Catfish. The Nassau grouper is a critically endangered species from the Caribbean, while the dusky grouper is threatened in the Mediterranean Sea. In both cases, something else entirely is frequently sold in their place, 3:D - Butterfish. Escolar is another common substitute. The high oil content and indigestibility of escolar has earned it the moniker “the laxative of the sea”. It is also often sold instead of white albacore tuna, to which it bears no relation except for its similar colour. Butterfish, similarly, bears no relation to white albacore tuna except for its smooth, fatty texture. Look out for the pinkish hue of true albacore tuna, 4:B - Skipjack tuna. Bluefin tuna is a highly sought-after delicacy for sushi, one of the reasons it has been so severely overfished. All three bluefin tuna species – southern, Atlantic and Pacific – are susceptible to collapse, and southern bluefin tuna is critically endangered. Bluefin commands high prices as a result – so if you can pass off a cheaper tuna species to unsuspecting customers, you can turn a healthy illicit profit, 5:A - Hoki is often swapped in for hake owing to its similar texture. Environmental groups have raised concerns about the overfishing of hoki in New Zealand, where it is a lucrative export, 6:D - While passionate regional debates rage on in the UK about the best choice for fish and chips, your cod may well have sneakily been swapped for haddock. Only a true aficionado could tell, 7:C - A family of flatfish called American sole. This is a species called Achirus achirus. The American seafood kingpin Carlos Rafael, known as “the Codfather”, bragged to undercover government agents that he had mislabelled 300,000 pounds of overfished American sole, which he was not supposed to have caught, as haddock. “This year I’ll have 15m pounds of haddock … I could never catch 15m. It’s impossible,” Rafael said. He was jailed in 2017 and fined more than $3m (£2m)

Scores

1. 7 and above.

   Like shooting fish in a barrel – there are no fakes on your plate

2. 0 and above.

   Better luck next time! You're not quite up to scale as a seafood detective

3. 4 and above.

   Not bad. You can spot a fish tale at a push