Biological aspects of the Bluntnose Sixgill Shark, Hexanchus griseus (Bonnaterre, 1788) in Tunisian waters: implications for fishery management

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Volume 15, Article 2

[Volume 15, Article 2]

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Sami MILI ⁽¹⁾

Raouia GHANEM ^(1,2)

Rym ENNOURI ⁽¹⁾

Dhaker TROUDI ⁽¹⁾

Hajer ZARROUK ⁽¹⁾

Samira JABBARI ⁽³⁾

¹Université de Carthage, Institut Supérieur de Pêche et d’Aquaculture de Bizerte, Unité de recherche : Exploitation des Milieux Aquatiques, Errimel, B.P.15. 7080 Bizerte, Tunisie.

²Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Biodiversité, Biotechnologie et Changement Climatique LR11ES09, 1002 Tunis, Tunisie.

³Faculté des Sciences de Bizerte, Zarzouna, 7021, Bizerte, Tunisie.

Abstract - The study of shark populations is crucial to ensure sustainable management of this exploited resource in Tunisia. It is within this objective that a study on the status of the bluntnose sixgill shark Hexanchus griseus fisheries in the Eastern Region of Tunisia was undertaken. A bottom longline fishing survey was conducted between March 2018 and July 2018 at depths ranging from 420m to 880m on a fishing boat operating at the Siculo-Tunisian Canal. A total of 83 specimens, with a total length ranging between 120 and 390 cm, were studied. Catches were more productive (76%) at a bathymetry of 750-900m compared to those of 500-750m and 300-500m. The study of reproductive parameters showed that the sex ratio was in favor of males (55.4%). The most captured individuals were immature. In addition, we noted the presence of a single pregnant female, 390cm in length, carrying 102 oocytes. Ecobiological parameters analyses statistics production revealed a very fragile stock of this shark species. Therefore, special attention should be given by fishery managers to provide a better conservation plan and a sustainable exploitation of this species in Tunisian waters.

Key words: Hexanchidae, Ecobiology, Fisheries, Central Mediterranean Sea, Stock, Elasmobranchs.