I am aware of the issue with parasites in fish, such that fish products that as intended to be eaten raw must be frozen to make them safe to eat. These regulations does not obviously include fresh fish, such as "sustainably sourced sea bass or sea bream fillets".

Fish freezing requirements

Freezing requirements apply to all food businesses that place fish and fishery products on the market such as restaurants, fish suppliers and fish buyers. This is to protect consumers from any harmful effects that might be caused by parasites that are naturally present in the fish.

Under food hygiene legislation, certain fishery products intended to be eaten raw need to be frozen before use.

Any treated products where the processing treatment doesn’t kill the parasites must also be frozen before consumption.

On the Guardian Newspapers website yesterday was released a recipe for ceviche that uses sustainably sourced sea bass or sea bream fillets and makes no mention of any procedure to kill parasites. Both these species are farmed in the UK and are available fresh. I have always assumed these would not be treated for parasites, as they are sold to the end user with the expectation they will cook the fish.

What is the general situation with fresh fish and parasites in the UK? Can one generally assume they will have been frozen? Should the guardian have put more of a warning on this recipe?

  • I think they should have put more of a warning, and indeed some of the comments underneath point this out ClausCPH: Maybe a word about parasites like tapeworms and like would be in order ?. I personally wouldn't trust any raw fish but to each their own, sorry to not know the answer to your interesting question, +1 regardless as I am curious too
    – JamesT
    Commented May 18, 2023 at 10:20
  • 2
    The UK has pretty good food standards, but I would use sushi fish for ceviche no matter what country I was in as it would have been deeply frozen to kill parasites.
    – GdD
    Commented May 18, 2023 at 14:31
  • Probably not. There are strict regulations in the UK. Check the Food Standards Agency page here - by law, some fish must fist be frozen before it is consumed raw.
    – Billy Kerr
    Commented May 19, 2023 at 13:39

1 Answer 1


Parasites are extremely common in both wild and farmed fish worldwide, from Australia to France. Studies show that in some places, over 80% of fish can have some kind of parasite*. There is no reason to believe that the UK is any different in this regard, even if UK Fisheries has decided not to publish statistics. Ignorance is not bliss, here.

Further, both climate change and introduced species have been making parasite infection rates worse, so that fish that used to be safe to eat unfrozen and raw aren't necessarily safe today.

So: Yes, the Guardian should have had a warning, and yes you should deep-freeze any fish before following the recipe.

(* most fish parasites cannot be transmitted to humans. Enough can for it to be a problem, though)

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.