There are two different, closely related, species. See:
http://www.nwrc.usgs.gov/wdb/pub/spe.../82_11-072.pdf
One is the sand seatrout, which is my best guess for the specimen in the picture. The other is the silver seatrout. I never work to hard to tell them apart. If it is over 12" it goes in the ice chest. Under 12", it goes on a hook.
I remember as a boy fishing in the channel at the jetties, I put a nice 15" sand trout on a stringer, and a while later pulled back in 1/2 a sand trout. I haven't used a stringer there since.