Big Ron ..."Alexander McTavish, my great grandfather who married Christina McNicoll, was probably born in Glassary (most of the censuses say this, although one says Castleron), as was his father Duncan McTavish. Alexander later lived in Glasgow, where he was a seaman, the master of one of the Clyde Trustee's sludge boats."
Castleron is actually Castleton that can be found in the lower right corner of this map just below Ballimore. It's east of Lochgilphead on the north shore of Loch Gilp; the point where it joins Loch Fyne.
http://www.streetmap.co.uk/map.srf?X=186500&Y=686530&A=Y&Z=120My MacTavishs' also came from this area of Glassary parish. Alexander McTavish (possibly of Ballibeg Aird) married Margaret Leitch circa 1790 (no marriage doc found). Their son, Lachlan, was living at Castleton Lodge at the time of his death in 1873 at the age of 71. I believe his widow Mary MacTavish (nee Campbell) and some of his children lived at Castleton after his death per census 1881. Lachlan does not appear to have a brother by the name Duncan although it does occur fairly regularly in the family tree. He did have a brother named Alexander b. 1806 but I have not traced that line out.
While Alexander Sr is listed as a crofter on Lachlan's death cert, Lachlan and his brother Hugh were fisherman. William Crawford, son of Alexander Crawford and Margaret McTavish and Son-in-Law to Lachlan, was also a fisherman. Alexander Crawford was listed as a fisherman on his wife's death certificate.