The reproductive physiology of gag grouper, Mycteroperca microlepis.

摘要

The gag grouper, Mycteroperca microlepis, is protogynous hermaphrodite distributed on reefs and hardbottom areas throughout the northern Gulf of Mexico and along the southeastern Atlantic Coast from Massachusetts to Florida. Gag stocks have greatly diminished in recent years and have experienced a dramatic shift in population sex ratio, resulting in the implementation of federal management strategies that require the closure of commercial trap fisheries and establishment of minimum size and bag limits in the rest of the fishery. Most gag are landed eviscerated, which creates problems for fishery biologists trying to monitor the reproductive health of gag stocks through fishery census because gonads are unavailable to verify fish gender and maturity.;This research was directed at developing the biotechnology to assess gender and maturational status in gag from which the gonads have already been removed, while generating the biological knowledge of gag reproductive physiology needed to evaluate potential impacts that fishing and shifts in sex ratio may have on their reproductive success. A secondary goal was to begin investigating the physiology and proximate causes of sex change in this species.;The specific objectives of this research were to: (1) describe the annual hormonal and gonadal changes associated with reproduction of female and male gag, (2) characterize these physiological parameters in fish undergoing sex reversal from female to male, (3) develop the biotechnology for biochemically identifying the gender and maturational status of individual gag, (4) validate the approach by comparison with conventional histological techniques, and (5) develop and verify size- and age-based maturity schedules for gag based on the new methods.;Only the reproductive cycle of female gag was characterized, as insufficient sample size precluded detailed analysis of male or transitional fish (objective 2). The reproductive cycle of female gag is similar to what is seen in other teleosts, with low circulating levels of sex steroids (estradiol-17;Development of a specific, rapid, and sensitive homologous gag VTG enzyme-linked immunosorbent assay (ELISA), in combination with radioimmunoassay (RIA) of the sex steroids, provided the basis for immunochemical assay of gender and maturational status of gag and other groupers. Analysis of VTG, estradiol-17