Pigfish don't get larger than 12" typically. They are described as a "palm-sized" fish. I'd say it's definitely some type of snapper, maybe gray or mutton. I've never caught either, so I'm not sure which that is.
Gray (aka Mangrove) Snapper:
http://indian-river.fl.us/fishing/fish/snapgray.html
http://www.basspro.com/webapp/wcs/st...ctType=article
.