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AbstractThe reproductive biology of red grouper Epinephelus moriofrom the inshore and offshore waters of the Yucatan Peninsula (Campeche Bank) was investigated over a 5-year period (1988–1993). Results confirmed that red grouper is a monandric protogynous hermaphrodite as shown by (1) the absence of primary males in samples, (2) the presence of transitionals in the population (1% of the total offshore catches), (3) the occurrence of a membrane-lined central cavity in the testes of all males and dorsal sinuses in the gonadal wall in most males, (4) the significant difference in size ranges and mean fork lengths of males and females, and (5) a female-biased male : female ratio in size-classes less than 72.0 cm fork length (FL). We found immature females all year round in inshore waters and immature females, mature females, and males, and transitionals in offshore waters. In the southern Gulf of Mexico, the species displayed seasonal reproduction, with single, annual peak spawning occurring in late winter and early spring (January–March). The greatest variations in the mean gonadosomatic index (GSI) of females were recorded between November (0.27%), February (2.14%), and April (0.17%) when they were ripening, ripe-running, or spent. Males were ripening between September and February, ripe-running from December through April, and spent in March. Spawning aggregations of red grouper were not observed. However, during the 1992 spawning period, 20 ripe-running females and 19 ripening and ripe-running males were caught near 20°47′N, 91°40′W on the western Campeche Bank on the second and fourth days after full moon. Sexual maturation in females occurred over a broad size range (38.9–72.0 cm FL). The size at first maturity, defined as length at which 50% of females were sexually mature (L50), was 50.9 cm FL ± 1.2 (mean ±SE). Sex inversion in females did not occur at a particular size or at a precise time. Size range and median size at which females change sex were 41.0–85.4 cm FL and 59.7 cm FL, respectively. Transitionals were caught during 5 months of the year, including two peak spawning months (January and February). Fishery management implications are presented and discussed.

The reproductive biology of red grouper Epinephelus moriofrom the inshore and offshore waters of the Yucatan Peninsula (Campeche Bank) was investigated over a 5-year period (1988–1993). Results confirmed that red grouper is a monandric protogynous hermaphrodite as shown by (1) the absence of primary males in samples, (2) the presence of transitionals in the population (1% of the total offshore catches), (3) the occurrence of a membrane-lined central cavity in the testes of all males and dorsal sinuses in the gonadal wall in most males, (4) the significant difference in size ranges and mean fork lengths of males and females, and (5) a female-biased male : female ratio in size-classes less than 72.0 cm fork length (FL). We found immature females all year round in inshore waters and immature females, mature females, and males, and transitionals in offshore waters. In the southern Gulf of Mexico, the species displayed seasonal reproduction, with single, annual peak spawning occurring in late winter and early spring (January–March). The greatest variations in the mean gonadosomatic index (GSI) of females were recorded between November (0.27%), February (2.14%), and April (0.17%) when they were ripening, ripe-running, or spent. Males were ripening between September and February, ripe-running from December through April, and spent in March. Spawning aggregations of red grouper were not observed. However, during the 1992 spawning period, 20 ripe-running females and 19 ripening and ripe-running males were caught near 20°47'N, 91°40'W on the western Campeche Bank on the second and fourth days after full moon. Sexual maturation in females occurred over a broad size range (38.9–72.0 cm FL). The size at first maturity, defined as length at which 50% of females were sexually mature (L50), was 50.9 cm FL ± 1.2 (mean ±SE). Sex inversion in females did not occur at a particular size or at a precise time. Size range and median size at which females change sex were 41.0–85.4 cm FL and 59.7 cm FL, respectively. Transitionals were caught during 5 months of the year, including two peak spawning months (January and February). Fishery management implications are presented and discussed.