Folk? probably. The words and tune of the chorus at least, if not the verses, seem to have been widely known among seafarers by the late 19th Century: Laura Alexandrine Smith's Music of the Waters (1888) puts it amongst her Tyneside material, and Stan Hugill's Shanties from the Seven Seas (1961) states:

... we next give a shanty in which the codfish and many other fishes figure. This song is called The Fishes, and although the original was undoubtedly a Scottish fisherman's song, it was sung aboard square-riggers at the capstan and often at pumps as well. The Scottish version of the chorus runs: "Blow ye winds southerly, southerly, southerly, Blow bonnie breeze, blow my lover to me." Another place of origin may have been the Tyne, as there does exist a keelman version.

He goes on to state that Colcord also collected the Scottish chorus from New England fishermen, whilst Whall (a Scot) gives a completely different tune. Hugill himself collected it from an old Bristol Channel seaman with a chorus of "Blow ye winds westerly, westerly, westerly, Our ship's in full sail, now steady she goes."