Biological and population aspects of the white shrimp Litopenaeus vannamei (Boone 1931), during the closed season 2006 in the Gulf of Tehuantepec, Mexico

During the period of closed season (June to August of 2006) of the Mexican shrimp fishery, three cruises of fishing prospection were made in the Gulf of Tehuantepec (southeast of Mexico), with the purpose of evaluating biological and population aspects of the shrimp species under commercial exploitation. In the particular case of white shrimp L. vannamei an accumulated sample of 2,905 items was analyzed, out of which 44.5 % were male and 55.5 % females (p>0.05), giving a generalized female/male (f/m) proportion of 1.2:1. Bathymetrically the main abundances were delimited by the 17 fathom (30.6 m) isobaths. In general terms the population was integrated predominantly by organisms with immature gonads (stage I), whereas the greater percentage of females with gonads in development (stage II) and sexually mature males (stage II) appeared in August. Spatially, the results showed that in this closed season the reproductive process (maturation and spawning) was developed with greater intensity in the subzones 92 to 95, between 12 to 16 fathoms (22m and 29 m). The mean length at first maturity (lm50) for females was 192 mm and 170.1 mm for males. Biometric relationships were established between total and abdominal length for the whole population and for independent sexes.