A few months ago I took out a wild salmon fillet I had in the freezer and left it to thaw for about 15 minutes in water. After it had partially thawed to the point where it wasn't hard, I filled my steamer pot with water and put it on a gas fire for about 20 minutes with the salmon inside.
When I took the salmon the out, I noticed there were 2 brown patches near different ends of the fillet. I took a bite of it and it tasted quite bad and way different to the normal steamed salmon I had before. I couldn't eat it so I threw it away but I was confused as to why did the salmon fillet turn brown when I steamed it? All the other times I steamed this same type of salmon it always came out pink.
The fillet in question is wild salmon from the Pacific.