The DEC confirms it - It was a Wild Atlantic Salmon

It is confirmed by DEC expert on the subject - the fish was a wild Atlantic Salmon:

From DEC's email:

"First, we got the opinion of Connecticut's salmon expert and he agrees with you. His response: "This is definitely an Atlantic salmon. Moreover, I do not believe that it is a hatchery fish—one of the broodstock that we stock into the Shetucket and Naugatuck rivers as part of the broodstock trophy fishery. I believe this to be a wild, post-spawned Atlantic salmon departing the Connecticut River, not entering it. I suspect that it entered the river last year, spawned, and was late to depart back to the ocean as a kelt due to the absence of a spring freshet. The fish is very skinny and not fully reconditioned as we would expect a bright incoming sea-return fish to have done. You can see that it is mostly head. It may have gotten lost in Long Island Sound and begun feeding and partially reconditioned."

Now the bad news. Atlantic salmon are an endangered species and you are prohibited by law to take or possess them. We know it was not intentional, and that the fish died because of bleeding. If you still have the fish or any parts of it, I'd ask that you please surrender it to DEC and we'll send it to Connecticut for analysis. I can make arrangements to have it picked up by Law Enforcement. We will not file any charges."

Since I have anticipated this answer I have saved tissue, scales and flesh along with high resolution pictures of the fish.

It is a little bit sad that I couldn't released this wild fish last Sunday. But it also may be the sign that environmental efforts are paying off and that fisheries around New York City are improving but we still do need to pay close attention to its fragile habitat.

An incredible wild fish and may be the sign that wild Atlantic Salmons are back