First Evidence of a Nursery Habitat for Juvenile Gag in the Southern Gulf of Mexico

Abstract

AbstractInformation on a nursery area for juvenile gag Mycteroperca microlepis in the southern Gulf of Mexico is offered for the first time in this study. A total of 817 gags that ranged in size from 1.5 to 34.5 cm standard length (SL) were captured with a small trawl net from January to December 2001 in a shallow sea grass bed (mainly turtle grass Thalassia testudinum, manatee grass Syringodium filiforme, and shoal grass Halodule wrightii). The gag biomass in the swept area was 217 ± 74 kg/km2 (mean ± SD) with a density of 48,393 ± 125 fish/km2. Peak ingress of gag was observed from March to May, when newly settled organisms (range, 1.5–2.8 cm SL; n = 28) and the smallest young of the year (age 0; 3.2–4.9 cm SL; n = 72) were caught. After settlement, juveniles reached maximum abundance by July (n = 186) with a size range of 8.0–18.2 cm SL and then began to leave the nursery area in September. The monthly occurrence of newly settled gag, length‐frequency analysis, and otolith aging indicate that age‐0 gag (range, 1.5–19.5 cm SL; n = 756) were present in this nursery area from March to December 2001 as a single discrete cohort. These results suggest that settlement is discontinuous for gag in this region. Back‐calculated hatching dates, estimated from otoliths of early juveniles captured in April (3.5–5.2 cm SL; n = 13), ranged between January 28 and February 10, 2001.