Having given the issue some thought this morning......
I think part of the debate comes down to what one accepts as "sea run." The traditional view and
stricter definition of sea run, of course, implies a trout that is spawned in freshwater, migrates literally out to sea; lives in the ocean for years, and then migrates back up the river to spawn. In other words, the same as steelhead. To some degree, such a plan was proposed with the Manasquan fish as it was hoped these fish would go out to sea and return. Could such a population exist in the Delaware? Sure. My personal view is that they
probably don't exist.....and I'll continue to be skeptical until I see something scientific and not anecdotal reports.
On the other hand, we all know that trout migrate long distances in PA warm water rivers on a seasonal basis. Shad and stripers, after all, migrate virtually the entire Delaware river length on a seasonal basis. It's certainly plausible that some browns that were spawned up in the NY section of the West Branch could, after the spawn, migrate downstream and lay up below Trenton for the winter and return in spring. Some might even be able to live in higher salinity sections of the river. This would be a less strict definition of "sea run." In New England, brook trout do something like this and are called "salters" or "sea run." Although they don't necessarily go out to sea,
the key is they are in genuine salt water at the mouths of coastel rivers and are feeding on marine organisms. Again, such a scenario is entirely possible in the D. So I suppose, if one accepts "sea run" to mean a population that drops down into brackish water or salt water in the lower reaches of a river.... then, using this less strict concept, I'd be more inclined to believe such fish exist. Browns that migrate up and down river on a seasonal basis don't qualify in my view as "sea run." If they get to salt water, then they can meet the less strict definition (I suppose). Part of this debate is where the salinity line is. I'd guess the salinity line is lower during colder months of the year due to higher flows and this would generally be in the vicinity of Philadelphia. Are there browns that far downriver this time of year on a regular basis? Perhaps. If one uses the less strict definition of sea run, than such fish would meet this standard.
Delware River Salt Line