We examined the hypothesis that individual red hinds, Epinephelus guttatus, evaluate future reproductive success and the best time to change sex from information available only within the annual spawning aggregation. Gonadal histology on individuals obtained from commercial catches
biweekly over a 2.5 year period confirmed that the species is protogynous and that ripe individuals are found primarily during the aggregation months of January or February. A gonadal index peaked sharply in January. Thus, fish reproduced largely within the aggregation time. The sex ratio
within the aggregation, 4.9 females per male, differed significantly from the sex ratio of 10.9 in inshore areas outside of the aggregation period. Individuals within the aggregation were significantly larger overall than individuals in inshore areas. Thus, for inshore populations, the information
needed in theory to assess when to change sex is only available within the aggregation. However, histologically discernible transitional individuals were found uniformly throughout the year, not primarily soon after the aggregation, as our hypothesis predicted. Additional study of deep, offshore
populations and further study of the earliest stages of sexual transition are needed to explain this discrepancy.
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