Well, Anglo, I listened again and to my ears it still doesn't sound a lot like the Fish song. Certainly the difference between the two is far greater than that between Fish song and the "My Jolly Roving Tar" (not the Harrigan song) collected in England 100 years ago, which are near identical apart from the repeat patterns (AABA in the Fish song, ABBA in the English trad one). Far more likely that the Fish melody developed from the English model, than by what would have to be fairly major transmutation of the Harrington. But maybe Mrs Fish (or someone else further up the line) had a copy of the (Harrigan) words with a chorus ending in the line "with my Jolly Roving Tar", and put them together with a different melody coincidentally bearing that title. The plot thickens........