What do the sustainability labels on fish actually mean?

Labels on fish do not work like organic labelling, where one mark covers the whole idea. Wild and farmed are certified by different bodies against different criteria, and a great deal of fish sold in the UK carries no certification at all without that meaning anything is wrong with it.

Step by step

1. Read the blue MSC tick as a wild-capture claim.Marine Stewardship Council certification assesses a specific fishery — a species, a stock, a gear type and an area — against stock health, ecosystem impact and management. It is about whether the fishing can continue, not about welfare or food quality.
2. Read the green ASC label as a farming claim.Aquaculture Stewardship Council certification covers farms: feed sourcing, water quality, disease and escapes, and social conditions. Salmon, prawns, tilapia, pangasius and mussels are the ones you will see it on most.
3. Use the Good Fish Guide for anything unlabelled.The Marine Conservation Society rates species-and-method combinations from 1 to 5, where 1 and 2 are green and best choices and 5 is red and to be avoided. It is free, searchable on a phone at the counter, and updated as stocks change.
4. Look at the catch method on the pack, not just the species.UK labelling requires the gear type. Line-caught, pot-caught, hand-dived and creel-caught are generally low-impact. Beam-trawled and dredged disturb the seabed heavily. The same species can sit at either end of the scale depending on this line.
5. Check the catch area code.Packs carry an FAO area — 27 is the North East Atlantic, 34 is the Eastern Central Atlantic, and so on, often with a sub-area. Stock health varies enormously between areas for the same species, which is why a rating is never just a species name.
6. Treat generic wording as meaningless."Responsibly sourced", "ocean friendly" and a picture of a boat are marketing unless they are attached to a named scheme. If there is no certifier and no method, you have no information.
7. Accept that supply is imperfect and choose the best available.Many good fisheries are not certified because certification costs money that a small fleet does not have. A local, in-season, line-caught fish from an uncertified boat can be a better choice than a certified one flown across the world.

Tips

• The easiest single improvement is to widen what you buy. UK consumption concentrates heavily on cod, haddock, salmon, tuna and prawns, and spreading demand across hake, coley, dab, megrim, pollack, herring, mussels and sardines takes pressure off the popular five.
• Farmed mussels and other farmed bivalves are among the lowest-impact animal proteins available — they need no feed at all and filter the water they grow in.
• Ratings change. A species that was red five years ago may be green now and the reverse happens too, so a remembered rule from an old newspaper article is not a current answer.
• Tinned tuna labelling is worth reading properly: pole-and-line or FAD-free caught skipjack is a very different product from unspecified purse-seine tuna, even in the same supermarket.

Common mistakes

• Judging by species alone — North Sea cod and Barents Sea cod are the same fish from stocks in very different condition, and hand-dived scallops and dredged scallops have almost nothing in common environmentally. Area and method carry most of the information.
• Assuming farmed always beats wild, or the reverse — Both range from excellent to poor. Farmed bivalves are outstanding, some farmed prawns are among the worst choices available, and well-managed wild fisheries beat both.

Questions people ask