Our Black lab "Jake" goes fishing with us all the time hence his AKC name "Opechee's Captain Jake". He is just one of a long line of fish dogs that we have had. We have used and English Setter, Gordon Setter, English Pionter, German shorthair a Beagle and a Hienz 57. as far as what dog works best for Salmon and Lake trout fishing belive me they all have thier strenghts. However the setters petty much hated water but that didn't stop them for perching themselfs on the motor cover or gunawale where the could fall over borad at any moment. The pointers were great fishing dogs also but they had a tendenacy to lap the slime of any fish you boated and keep and somtimes they would keep this lapping up for hours. Also if you put a fish on a stringer they would stare over the side of the boat at it for hours too. The black labs I think are perhaps the best and most trainable dogs for fishing and they were orignaly breed for fishing not hunting to begin with.
But almost any dog can be a good fishing dog size and color doesn't appear to matter that much : ) I might also add most of the above dogs were Excellant Bird dogs in the off season.