Reproductive biology and space–time modelling of spawning for sailfish Istiophorus platypterus in the western Atlantic Ocean

ABSTRACT

This study presents data and estimates reproductive parameters of the sailfish Istiophorus platypterus (Shaw, 1792) in the western Atlantic, useful for future stock assessments of the species in the Atlantic Ocean. During the period 2006–2011, a total of 1132 fish were sampled by scientific observers on board Venezuelan and Brazilian longline vessels and from artisanal fisheries based out of Cumaná, Puerto La Cruz and Playa Verde, Venezuela and Cabo Frio, Rio de Janeiro, Brazil. The ovaries of 543 females were classified into five ovarian development phases based on microscopic analysis of the most advanced group of oocytes. Generalized additive models were applied to the gonadal index and sex ratio data in order to assess spatio-temporal trends of the reproductive activity and identify the spawning areas. Space–time effect was a significant factor contributing to changes in sex ratio and reproductive activity. Spawning activity was observed in two distinct areas. On the south-east Brazilian coast spawning peaked during December–February, while in the south-eastern Caribbean Sea spawning occurred between March and September, with its peak in March and April. Using a Bayesian approach, size at 50% maturity was estimated to be 146.12 cm (credibility interval of 95%, 138.45–152.09 cm). Batch fecundity ranged from 436,800 to 2,492,500 hydrated oocytes per female. This study confirms multiple aggregation spawning for this species in the western Atlantic Ocean.

SUBJECT EDITOR:

• Audrey J. Geffen

KEYWORDS:

• Sailfish
• Istiophorus platypterus
• sex ratio
• spawning season
• fecundity
• maturity

Acknowledgements

The authors gratefully acknowledge the scientific observers and port samplers of ICCAT's Enhanced Research Program for Billfish in Venezuela and Brazil for collecting the data and samples for this study. Special thanks go to Dr David Kerstetter for thoughtful comments and suggestions on earlier drafts of this paper and Eduardo Pimenta for help in getting samples from Cabo Frio, Rio de Janeiro. We also thank Cezar Fernandez, Vanessa Basante, Patricia Pinheiro, Marly Medina and Alejandro Ariza for help in processing samples in the laboratory.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Part of this study was funded by the National Council for Scientific and Technological Development (CNPq, Brazil - 140329/2008-0).