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New insights on Reproductive strategy of swordfish ( Xiphias gladius )

F.Poisson. Fauvel C. New insights on Reproductive strategy of swordfish ( Xiphias gladius ) In the Southwestern Indian OCean. Part 2: Fecundity and spawning pattern. Close to over-exploitation (IOTC). 35,000 Tonnes. 1990. Aims of this study.

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New insights on Reproductive strategy of swordfish ( Xiphias gladius )

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  1. F.Poisson. Fauvel C. New insights on Reproductive strategy of swordfish (Xiphias gladius) In the Southwestern Indian OCean

  2. Part 2: Fecundity and spawning pattern

  3. Close to over-exploitation (IOTC) 35,000 Tonnes 1990

  4. Aims of this study • Monitor the gonadal development of individuals around Reunion Island, • Review all information available in the Indian and western Pacific Oceans.

  5. Sampling program Over 32 CONSECUTIVE MONTHS • 52 trips onboard domestic longliners • 294 days at sea, 235 longline sets • 1727 gonads sampled

  6. Spawning occurs from October to April Gonadal Index (Hinton et al. 1996) Spawning Threshold value 1.375

  7. Spawning season is longer for bigger (older) females

  8. The Big individuals arrived at the beginning of the Spawning season

  9. Sex ratio fluctuated seasonalyaccording to SST

  10. Millions of oocytes Batch fecundity increases with the fish weight (age)

  11. Big Old Fat Fecund Female Fish (BOFFFF) hypothesis(Longhurst 2002, Berkeley et al. 2004) Diameter of eggs ☺ ☺ offsprings Viability ☺ Growth BOFFFF more biologically valuable

  12. Spawning activity is localized in discrete areas

  13. Conclusion • Spawning activity localised in discrete areas • Synchronised movements between spawning ground and neighboring regions • Major role of the BOFFF in the reproductive capacity

  14. PROSPECTS • Confirm migration pattern (homing pattern) • Consider the protection of BOFFFF • How to preserve the population age structure • Fishing closure ? • Protected marine areas? • Gear selectivity ?

  15. Acknowledgements This project was an financed by the European Union (FEDER), and the Conseil Régional and Conseil Général de La Réunion. The authors would like to express their gratitude to the skippers who volunteered to allow scientific observers on board their vessels and to all people involved in the sampling. We thank the fishery industry of Reunion Island for their outstanding support of the “Programme Palangre Réunion” (PPR) project.

  16. THANKS FOR YOUR ATTENTION DO SWORDFISH ♂ PREFER THE BOFFFF ?

  17. Histological analyses Maturity scale for females Ovocyte diameters Distribution Stages 0 undeveloped 1 Immature developing 2 3 maturing Transverse section of a an early developing ovary stage 4 ripening 5 Spawning 6 Spent or resting Transverse section of a a ripe ovary in hydratation Spawning occurs in the vicinity of Reunion Island

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