Fortunately this has, I believe, largely changed to frozen ingredients; i.e., cheaper from Makro and the like. Storage and transportation is also cleaner and easier for the sellers.
My missus has never bought seafood from the markets and warned me years ago about the commonplace use of formalin there. Just recently I was reminded of this when buying cooked seafood on 2 different occasions; bbq scallops (Coquille St Jaques) and the griddled squid roe which is very popular now. Both tasted good and fresh and were cooked well but left me with a bitter aftertaste in my mouth. I wondered if this was due to formalin.