Mark,
As regards identification, there are a few points on the fish that makes me THINK its a seatrout.
First of all, the tail fin. There is no evidence of a fork in it. Salmon have a pronounced concave tail fin with an indentation in the centre. Second, the wrist of the tail is too stocky and not thin enough. Third, there are too many spots below the lateral line.
The evidence for a salmon is the head. The eye SEEMS to be set far back. Yet I've caught a few big cock rainbows in my life with heads shaped like this.
I don't want to be dogmatic however.
It could also be a hybrid.