Life History of Juvenile Gag, Mycteroperca Microlepis, in North Carolina Estuaries

Gag, Mycteroperca microlepis, is the most abundant and widely distributed of the seven grouper species that may occur as juveniles in North Carolina estuaries. Gag larvae migrate from offshore spawning areas to high salinity estuaries and are most common in seagrass beds. Monthly collections (1981–1982) revealed that young gag first appeared in grass beds in mid–late April at 13–16 mm SL (mean = 14.9 mm). They reached maximum abundance by May or June (mean size = 31.6 mm) and by September attained lengths of 99–186 mm (mean = 132.3 mm). With growth, many gag moved from grass beds to other complex estuarine habitats. Most young-of-the-year gag left the estuaries for offshore reefs during mid-late autumn, and cold weather fronts may have precipitated these emigrations. Gag were carnivorous throughout their estuarine period. Fish <70 mm fed mainly on copepods, amphipods, and Palaemonetes spp. As they grew, gag fed more on larger crustaceans and other fishes. We determined meristic values of all grouper collected; however, color patterns were most useful for identifying all juvenile groupers. The weight-standard length relationship was: W = 1.9 × 10⁻⁵(SL)^3.04, N = 244, r ² = 0.99. The TL-SL regression was: TL = 1.03 + 1.22(SL), r ² = 0.99.