Analogues: Larval S. tabacarius have a melanophore at the base of the upper segmented caudal-fin rays while larval S. tortugarum have no melanophores on the caudal fin. Larval S. baldwini and S. tigrinus differ by having internal melanophores at the mid-body and under the last dorsal-fin spine and the melanophores along their dorsal-fin membranes are on the distal third (not proximal). Larval Diplectrum bivittatum differ by having a full row of melanophores along the anal-fin base and the row continues along the ventral midline of the caudal peduncle.
Diagnosis: Modal fin-ray counts of D-X,12 A-III,7 with 15 pectoral-fin rays indicate several Serranus species and Diplectrum bivittatum. Serranus tabacarius is the only shallow-water species with this modal fin-ray count (deep-water species comprise S. maytagi, S. notospilus, and S. phoebe).
Transitional S. tabacarius can be distinguished from S. tortugarum by developing a single large patch of melanophores along the spinous portion of the dorsal-fin membranes vs. two. They have no obvious stripes radiating from the eye as are found on transitional S. tigrinus and S. baldwini. Transitional Diplectrum bivittatum differ by having a prominent mid-lateral body stripe and a distinctly narrower body.
Description: Body thin and moderately wide with a round eye and a very large terminal mouth. Pectoral and pelvic fins long, reaching just past the vent, dorsal-fin base long and anal-fin base short, caudal peduncle relatively short and not wide. (The third spinous-dorsal-fin membrane is greatly extended, up to 3 times the length of the next membrane)?. On the head there is a melanophore at the angle of the jaw. Later larvae can have additional spots on the head, just above and behind the upper eye, a spot over each lobe of the brain, and a small midline patch just behind the brain. On the body, there are melanophores only along the ventral midline of the caudal peduncle, one just after the last anal-fin element and one or two just before the procurrent caudal-fin rays. Internal melanophores line the dorsal aspect of the swim bladder and posterior peritoneum (no internal melanophores in the mid-body or tail). There is the standard serranid speckling on the pelvic-fin membranes and on the outer half of the pectoral-fin membranes. There are melanophores along the membranes of the posterior spinous dorsal fin (sixth to ninth). On the base of the anal fin there are one or two melanophores, usually on the first soft ray and often the third or fourth. Notably there is a melanophore at the base of one (or a few) of the mid-upper segmented caudal-fin rays.
