New insights on Reproductive strategy of swordfish ( Xiphias gladius )

New insights on Reproductive strategy of swordfish (Xiphias

gladius) In the Southwestern Indian

OCean

F.Poisson. Fauvel C.

Part 2: Fecundity and spawning pattern

Close to over-exploitation (IOTC)

35,000 Tonnes

1990

Monitor the gonadal development of individuals around Reunion Island,

Review all information available in the Indian and western Pacific Oceans.

Aims of this study

Sampling program

Over 32 CONSECUTIVE MONTHS

52 trips onboard domestic longlinersonboard domestic longliners 294 days at sea, 235 longline sets 1727 gonads sampled

Spawning occurs from October to April

Threshold value1.375

Gonadal Index (Hinton et al. 1996)

Spawning

Spawning season is longer for bigger (older)

females

The Big individuals arrived at the beginning of the Spawning season

Sex ratio fluctuated seasonaly according to SST

Batch fecundity increases with the fish weight (age)

0

5

10

0 150 300

fish weight (kg)

Millions of oocytes

Big Old Fat Fecund Female Fish (BOFFFF) hypothesis

(Longhurst 2002, Berkeley et al. 2004)

Diameter of eggs

offsprings Viability

BOFFFF more biologically valuable

Growth

☺

☺

☺

Spawning activity is localized in discrete

areas

Spawning activity localised in discrete areas

Synchronised movements between spawning ground and neighboring regions

Major role of the BOFFF in the reproductive capacity

Conclusion

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 ?

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.

THANKS FOR YOUR ATTENTION

DO SWORDFISH ♂ PREFER THE BOFFFF ?

Spawning occurs in the vicinity of Reunion Island

Histologicalanalyses

Transverse section of a an early developing ovary stage

Transverse section of a a ripe ovary in

hydratation

Stages

1 Immature

2

3

4

5

6

developing

maturing

ripening

Spawning

Spent or resting

Maturity scale for females

0 undeveloped

Ovocyte diametersDistribution

0

0,05

0,1

0,15

0,2

0,25

0,3

0,350

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35