No abstract

Sex ratio, size at maturity, reproductive periodicity, ovarian development pattern, and spawning ground data for red snapper Lutjanus campechanus from the southern Gulf of Mexico were analyzed to understand this species' reproductive biology throughout its geographical distribution. Red snapper were sampled in 1999 and 2000 from commercial fishery catches taken on Campeche Bank at depths ranging from 43 to 130 m. Overall sex ratio (male : female) and sex ratios by size-class did not differ significantly from a 1:1 ratio. First maturity was at a slightly smaller size in males (24.2 cm total length [TL]) than in females (28.3 cm TL), and maximum length percentages at first maturity were 28% for males and 34% for females. The length at which maturity was attained in 50% of females (L50) was 31.4 cm TL. The Campeche Bank red snapper stock had a protracted spawning period from February to November, with a spawning peak occurring in early fall. Vitellogenic oocytes were continually recruited from previtellogenic oocytes during the entire spawning season, with no gap between each oocyte development stage. This means that red snapper ovaries are asynchronous and that the species can be considered a heterochronal (batch) spawner with indeterminate annual fecundity. Females in spawning condition were collected from both the northeastern and northwestern areas of Campeche Bank, near submerged or emergent coral reef structures, and at depths between 48 and 117 m. These results generally agreed with those for red snapper stocks in others regions of the Gulf of Mexico and the Atlantic Ocean off the southeastern United States. However, reproductive periodicity in the Campeche Bank red snapper stock apparently displayed more of an insular pattern of extended spawning in comparison with the typical continental pattern of restricted spawning reported for other regions. The latitudinal differences observed in red snapper spawning seasons could also reflect a latitudinal gradient in the intensity of seasonal environmental constraints.

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.

Despite its commercial importance and high vulnerability to fishing impact, little is known about the reproductive biology of the Tiger Grouper Mycteroperca tigris, an aggregative spawner. We studied the key reproductive parameters of this species in the southern Gulf of Mexico, where the grouper fishery is generally in decline. The smallest mature female measured 31.4 cm FL, and length at which maturity was attained in 50% of females (L50) was 34.2 cm FL. Tiger Grouper are protogynous hermaphrodites, and the estimated length at which 50% of females had changed sex was 51.9 cm FL. Spawning season lasted from February to June, with a spawning peak observed in April. Most of the actively spawning females were collected 7–14 d after the full moon in April and May. Females exhibited continuous, asynchronous oocyte development and batch release of mature oocytes. During April–June, estimated spawning interval varied monthly from 1.8 to 4.3 d (mean = 2 d). Due to the species’ indeterminate fecundity, we estimated batch fecundity, which ranged from 84,119 to 1,032,578 oocytes (mean ± SE = 417,102 ± 34,826 oocytes). Conservation status of the Tiger Grouper in its distribution area is currently unclear. Based on the observed maximum sizes for both sexes and the size of sexual transition, the southern Gulf of Mexico Tiger Grouper population may be healthier than some Caribbean Sea populations. Current and potential measures for regulating this fishery resource in the southern Gulf of Mexico are discussed.