The Food Safety (Fishery Products and Live Shellfish) (Hygiene) Regulations 1998

1.  Fishery products must, during storage and transport, be kept at the temperatures laid down in these Regulations, and in particular—

(a) fresh or thawed fishery products and cooked and chilled crustacean and molluscan shellfish products must be kept at a temperature approaching that of melting ice;

(b) frozen fishery products, with the exception of frozen fish in brine intended for the manufacture of canned foods, must be kept at an even temperature of −18°C or less in all parts of the product, after temperature stabilisation, and allowing for the possibility of brief upward fluctuations of not more than 3°C, during transport.