How do you cook blue fish and can you get blue fish in the UK.?

I ate blue fish in an Italion restaurant in Washington DC and I think there was garlic in it. it was delicious.How do you cook blue fish and can you get blue fish in the UK.?
i'm in the uk and i've never heard of blue fish never mind had itHow do you cook blue fish and can you get blue fish in the UK.?
The only blue fish i can think of is bleu trout , this is where you kill the trout moments before you cook it and the skin takes on a blue tinge, pretty barbaric if you ask me that might be what you are thinking of sorry i can't be more help