Spawning Cycle, Sex Ratio, and Weights of Blue Marlin off Puerto Rico and the Virgin Islands

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Abstract
Pronounced cyclic changes were discovered in the gonad sizes of 263 male and 65 female blue marlin, Makaira nigricans Lacépède. Fish with ripe testes were found from May to November. A prespawning enlarged testis stage preceded the smaller ripe stage. Ripe testes became smaller in average size as the season progressed. The postspawning stage was notably smaller than the ripe stage. Critical stages were determined or confirmed by histological sections. Testis weight related to body weight, in percent, increased as much as 17 times from the postspawning to prespawning stage in adult males. Developed ovaries were observed from late May to September, and one female was ripe in September. The peak of the spawning period appeared to be July and August, when males and females were present in equal numbers. The largest male weighed 297 lb; and the largest female, 814 lb. Females over 400 lb. were most frequent in the July catch, and second most frequent in August. There were 11 females in the modal weigh...

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