Yeah Ho Little Fish(es) (both Gordon Bok and Ed Trickett have recorded this, in slightly different versions)

Gordon Bok's Herring Croon

Shelly Posen's "No More Fish, No Fishermen" (about the results of overfishing -- good for older kids). FinestKind has recorded it.

Stan Rogers' "Make and Break Harbor" (again, about the decline of the fishing industry)

"I Lost Her in Gloucester" (a humorous song with lots of groany puns based on the names of fish/sea creatures)

Archie Fisher's "The Final Trawl" (older kids again -- yet another about the decline of fisheries)

Those are a few that come to mind off the top of my head. Try running a search on the DT -- I'm sure some of these, at least, will be there. If you can't find words/tunes, send me a PM and I'll try to help. Kathy