Trout in the Merrimack (in Massachusetts)? Maybe where The Shawsheen River empties in Lawrence? As far as Salmon, can't say you won't catch one, but the stocking program ended a couple years ago, they just wouldn't take. Who would have thought 200 years of industry damming and pollution would do that? I did see an angler take in a salmon behind the dance studio in Andover (by the R&R tracks), like I said, not impossible, just not likely.