Reproductive biology of the sailfish Istiophorus platypterus in the Acapulco Bay, Mexico

Background. The sailfish Istiophorus platypterus is an oviparous billfish species (family Isthiophoridae); it is caught by trolling in the sports fishery in Mexico. However, to date, there have been no reproductive biology studies of sailfish in Acapulco Bay, although the reproductive aspects of any species represent essential information for the design of management plans. Goals. Provide information on aspects of the reproductive biology of sailfish in waters off Acapulco, Bay. Methods. During the period 2008–2009, a total of 561 fish were sampled. Macroscopy analysis and quantitative histology was used to describe reproductive characteristics of the sailfish gonads. Results. 55.8% of the analyzed organisms were males, the remaining 44.2% were females, the sex ratio (1.26 M: 1 H) was different from the expected theoretical ratio. The ovaries of 155 females were classified into five ovarian development phases based on histological analysis of the most advanced group of oocytes. Sailfish is a multiple spawn with asynchronous oocyte development. Batch fecundity for 14 females with the presence of hydrated oocytes ranged from 0.330 to 2.092 × 10 oocytes with an average of 1.07 × 106 oocytes. Gonadosomatic index (GSI) indicated that sailfish have a reproductive period with peaks in August and October (mean monthly GSI= 4.3% and 5.4%, respectively). Conclusions. Population sailfish in the Bay of Acapulco is composed mainly of males, with a reproductive maximum in the case of females during the warm months of the year, as well as a relatively high fecundity.