Yesterday we bought some wet fish from Morrisons, (fresh ray wings) and it
said on the packet use by 21 august which is today. (I know that's cutting
the time window a bit fine) Also there was a sticker on it saying prepared
in this store, which i guess might mean it was transferred from the fish
counter into a packet and then placed on the shelves,

It tasted and smelt of ammonia and it was too awful to eat. I've heard of
dodgy meat departments rinsing old meat in a dilute bleach solution to
freshen it up.

Is it possible a similar thing is being done with fish would you guess?
But someone got the dilution rate wrong. Or is the ammonia always part of a
too old fish smell and taste ?