ASPECTS OF THE LIFE-HISTORY OF THE YELLOWMOUTH GROUPER, MYCTEROPERCA-INTERSTITIALIS, IN THE EASTERN GULF-OF-MEXICO

We describe the life history of yellowmouth grouper, Mycteroperca inte rstitialis, using specimens captured at the Florida Middle Ground in t he eastern Gulf of Mexico between May 1978 and July 1992. Spawning occ urred throughout the year; peak activity was observed during April and May. Yellowmouth grouper are protogynous hermaphrodites: sex-inversio n was documented for five individuals, younger/smaller individuals wer e female, and most older/larger fish were male. Females began to matur e at 400 mm total length (TL) or age 2; all were mature by 450 mm or a ge 4. Transitional fish ranged 505-643 mm and were 5 to 14 years old. The smallest and youngest mature male was 505 mm and age 4. Ages could be readily determined from otolith sections because they contained di stinct opaque bands that formed during the late summer and fall. Femal es ranged 2 to 17 years old; males were 4 to 28 years of age. Annual g rowth of yellowmouth grouper averaged greater than 200 mm or 470 g dur ing their first 2 years of life and then slowed thereafter to about 18 mm or 221 g for females and to about 10 mm or 190 g for males. Signif icantly different linear growth models fit sex-specific length-at-age and weight-at-age data well. Length-age and weight-age relations for a ll fish were: 1(t) = 828 (1 - exp(-0.076(t + 7.5))) and w(t) = 13.9 (1 exp(-0.022(t + 1.4))), where 1(t) is TL in mm, w(t) is weight in kg, and t is age in years. The pooled estimate of total annual mortality f or ages 8-18 during 1978-1992 was about 25%. Because of similarities i n their morphology and habitat preference, we compared our findings fo r yellowmouth grouper with life-history aspects of its closely related congener, the scamp (M. phenax).