Of the 100 or so species of fish available to be hooked from the pier, only about a dozen are regulated.
That's a good place to start ;-)
http://www.outdooralabama.com/sites/...20printing.pdf
Of those 12-15 species, only 8 can be referred to as 'common' catches on the pier.
So I put them on the back of my business card...
http://www.gulfshorespierfishing.com...tid=6538&stc=1
Easily THE most commonly caught regulated fish on the GSPPier would be Spanish Mackerel,
and they don't even have a length requirement.
They are however, easily confused with juvenile king mackerel, which must measure at least 26" fork length (FL).
Learn to tell the difference:
http://www.gulfshorespierfishing.com...tid=6539&stc=1
And since shark fishing is taboo on the pier, IDing those species is rendered irrelevant.
The rest should be easy ;-)