Reproductive biology of gag in the southern Gulf of Mexico

Abstract

Aspects of the reproductive biology of gag Mycteroperca microlepis in the southern Gulf of Mexico were studied by following seasonal variations in the gonado-somatic index and through histological examination of gonads. Gag were collected from inshore and offshore waters of the Campeche Bank, Yucatan, Mexico, between April 1996 and December 2001. This species is a protogynous hermaphrodite, and appeared to be depth-size distributed. The smallest gag (9-49 cm L F ) collected were all juvenile females, and were caught in inshore waters (1-10 m depth), while the largest (49-116 cm L F ), mainly adult females, males and transitionals, were captured in offshore waters (33-167 m depth). Overall the offshore male to female ratio was female-biased (1 : 3Á3) and differed significantly from unity. The species spawns at depths of c. 50-53 m, from early winter to mid-spring, with peak spawning activity occurring between January and March. Fifty per cent of females reached first maturity at 72Á1 cm L F . At 103 cm L F , 50% of sampled females had changed into males. Gag can be considered a monandric species, and sexual transition for this grouper seemed to occur in fish distributed within a narrow size range (85-111 cm L F ). The results are compared with those of other authors for gag stocks from the south-east Atlantic coast of the U.S.A. and the north-east Gulf of Mexico.

Reproductive biology of the island grouper (<i>Mycteroperca fusca</i>) in the Canary Islands, northwest coast of Africa

“…Similarly, Bullock and Murphy (1994) and Collins et al (1997) indicated that transitional specimens have typically represented less than 1-2% of samples. Protogynous hermaphroditism in M. fusca is in line with the pattern of sexual reversal described in other species of the genus, such as M. rubra in Mediterranean waters (Heemstra and Randall, 1999), Mycteroperca phenax Jordan and Swain, 1884 along the coast of the west-central Atlantic (Harris et al, 2002), M. bonaci (Brulé et al, 2003a), Mycteroperca intertitialis (Poey, 1860) (Bullock and Murphy, 1994;), and M. microlepis (Crabtree and Bullock, 1998;Collins et al, 1997;Brulé et al, 2003b) and Mycteroperca tigris (Valenciennes, 1833) (García-Arteaga et al, 1999) in the waters of the east Atlantic, which clearly reveal this as a characteristic of the genus.…”

“…The growing oocytes were classified according to the six histological stages proposed by Moe (1969) specifically for groupers, modified by Brulé et al (1999) for Mycteroperca species and extensively used for this genus (Brulé et al, 2003a, b;Tuz-Sulub et al, 2006): I, primary oocyte; II, immature oocyte; III, oocyte in primary vitellogenesis; IV, oocyte in early secondary vitellogenesis; V, oocyte in late secondary vitellogenesis; VI, mature and hyaline oocyte. The criteria described by Shapiro et al (1993) for grouper and by Brulé et al (2003b) for Mycteroperca species, and extensively applied as criteria in grouper species (Sadovy and Colin, 1995;Rhodes and Sadovy, 2002), were used to distinguish a resting mature female from an immature female based on the presence of muscle bundles remnants and connective tissue surrounding blood vessels. Testes were classified according to the most advanced stage of spermatogenesis observed.…”

“…Testes were classified according to the most advanced stage of spermatogenesis observed. The spermatogenesis was classified under four histological categories: spermatogonium, spermatocyte, spermatid and spermatozoa, based on a modified criteria of Brulé et al (2003b). Males were classified by the presence or absence and relative proportions of germinal stages, in conjunction with structural aspects of the gonad.…”

“…The reproductive period was defined for both sexes using the relative proportion of animals in each sexual stage and by examining seasonal variations in the gonado somatic index (GSI=100GM/TM) (Brulé et al, 2003b).…”

Oocyte development and fecundity type of the Brazilian Snapper Lutjanus alexandrei Moura & Lindeman, 2007 (Perciformes: Lutjanidae)

“…This was clearly observed due to the presence of a gap in the oocyte size frequency distribution between hydrated oocytes and advanced yolked oocytes in the actively spawning phase BrownPeterson et al, 2011). Multiple spawning is a condition reported for many other coral reef fish species, such as Nassau grouper Epinephelus striatus (Bloch, 1792) (Colin, 1992), inshore coral trout Plectropomus maculatus (Bloch, 1790) (Ferreira, 1993), gag Mycteroperca microleps (Goode & Bean, 1879) (Brulé et al, 2003), coney Cephalopholis fulva (Linnaeus, 1758) (Trott, 2006), white grunt Haemulon plumieri (Lacépède, 1801) (Palazón-Fernandéz, 2007;Shinozaki-Mendes, 2013a, b), and mutton hamlet Alphestes afer (Bloch, 1793) (Marques and Ferreira, 2011). Overall, coral reef fish species present a variety of complex spawning systems, but among them two major groups are generally observed: (1) demersal spawners, showing a synchrounous oocyte development and total spawning, represented mainly by species of the families Gobiidae, Blenniidae and Pomacentridae; and (2) pelagic spawners, exhibiting asynchronous oocyte development and spawning in portions, represented by families such as Lutjanidae, Haemulidae, Carangidae, Mullidae, and Gerreidae (Rong-Quen, 2000;Petersen and Warner, 2002).…”