Snuffy, just guesses.
Speculation about the song is that variants of the song reached Canada from France and the Channel Islands in the 17th c., but little to back that up. Only fragments (e.g. Chantey song, coll. Creighton). It has musical elements found in French Coastal songs (see le chasse-marée), but nothing concrete. I have just the first four "Cahiers de chants de marins" from Chasse-marée and one French marine song cd of the many, a poor representation, so I only have a 'feeling' that the song is French about vessels working towns along the French Atlantic coast, and that perhaps the Jersey version may be close to an older French song. Porchémue of the song is an old French name for Portsmouth.