Well, thanks for all your comments and opinions, this is a brilliant forum.
Sheryl has summed it up, has it says 70% white fish (I am probably being a bit naive here but) I would expect some flesh, although I know not all fish flesh is white.
I don't have a problem with heads or skins, Ozzy has the dried fish skins has treats.
I think I was a bit shocked with their reply, they also mention "frames and trims" not sure exactly what the frames would be but take it to mean back bones etc.
I know most dogs can eat almost anything but I have to be careful because of his sensitive tummy. Which is why he eats mainly fish and why I queried the colour of this food. We have tried other fishy wet foods but they are usually a light beige colour, WWs was a very, very dark brown.
I have tried different foods for him, even raw, but he seems to be settled on fish.
I will not be giving him the WWs wet food. Although I have to say he has WWs dry salmon and potato for breakfast and this food helped to get his stomach sorted. I just like him to have a wet food for tea (that's just me).
JeffD, thanks for the link to orijen food, it reminded me that we tried a sample of this about 18 months ago and at the time it did not suit him
but it may be worth trying again has his stomach is now much more settled.
Dog food is such a minefield.
Once again thanks for taking the time to reply to my post.