Seasonal reproduction of sailfish Istiophorus platypterus from the southeast Mexican Pacific

Abstract

Quantitative histology was used to analyse the seasonal reproductive characteristics of the Istiophorus platypterus sailfish obtained from bycatch and recreational catches in the southeast Mexican Pacific. The analysis revealed five stages of ovarian development, eight kinds of oocytes, and one postovulation structure. The species shows an asynchronous ovary development and indeterminate fecundity. Gonadosomatic indices (GSI) indicated that sailfish have a reproductive period with peaks in September and October (mean monthly GSI=1.9 and 1.8). Females were more abundant during the second quarter, whereas males were more abundant in the third and fourth quarters. We found that the estimates of the frequency distribution of whole oocytes showed that this analysis may be useful as a tool to assess maturity. The estimated size at sexual maturity for this species in the Gulf of Tehuantepec was 150.2 cm eye–fork length.