Are black prawns safe to eat I bought some prawns yesterday at a supermarket. Although displayed on the fish counter with fresh fish, they were clearly frozen or partially frozen. I put them in the fridge over night. 

Today, I've noted they've turned black. After a little research, it shows this could be due to oxidation, although others have commented they've never seen this before even if they've worked in "the" industry.

And one comment suggested that any black on prawns means they're spoiled and should be binned/destoryed. This is the part I'm sure of.

 

I have tried to wash with running water and can't remove this black colour.

There is no unexpected odour. 

Sadly, I've also noted that the squid which I bought has released its link. Although all this fish was in the same outer bag, the squid was it its own bag and it doesn't appear to have leaked.

After taking the shell off, there isn't really any colouration to the flesh.

Is is possible to know if they are safe. Is this a known thing - that prawns turn black and it means either oxidation or that they're spoiled?
They look like they have been blanched. Or dipped in boiling water. The red.This is some times done if they have parisites on them. But froze? &amp; shipped?  I am talking about prawn fresh of the boat at home. Then blanched &amp; froze at home for later use.  I would avoid these if store bought. If I did not know they were boat fresh. How handled. Many prawn &amp; shrimp are black in color. But not like that.