|Titre||Shark by-catch observed in the bottom longline fishery off the Kerguelen Islands in 2006–2016, with a focus on the traveller lantern shark (Etmopterus viator)|
|Type de publication||Conference Proceedings|
|Year of Conference||2017|
|Auteurs||Chazeau, C, Iglesias, S, PERON, C, Gasco, N, Martin, A, Duhamel, G|
|Conference Name||The Kerguelen Plateau: marine ecosystem and fisheries.|
|Edition||Welsford, D., J. Dell and G. Duhamel|
|Mots-clés||abundance, Distribution, Elasmobranchs, length frequency, longline fishery, Southern Ocean|
Data collected by fishery observers on board French fishing vessels targeting Patagonian toothfish (Dissostichus eleginoides), were examined to quantify and describe shark by-catch within the Kerguelen exclusive economic zone (EEZ). From 2006 to 2016, the fishing crews of longline vessels reported the total catches of the line and observers were asked to identify and count fish by-catch on 25% of the total fishing effort. A total of 26 203 longline hauls and more than 55 million hooks were checked by observers reporting 29 500 individual sharks caught as by-catch. Four shark species were identified (traveller lantern shark – Etmopterus viator, southern sleeper shark – Somniosus antarcticus, Portuguese dogfish – Centroscymnus coelolepis and porbeagle shark – Lamna nasus) among which E. viator was numerically largely dominant (99%). Relative abundance (number of shark per 1 000 hooks observed) calculated for sets with sharks present, was used to show bathymetric and geographical distributions and biological data were analysed. There were marked differences between distributions of the shark by-catch species and their relative abundance. This study is a major contribution to the ecological knowledge of E. viator with a detailed description of its distribution, the deepest record for the species (1 951 m) and the updated length at first maturity for female (48.5 cm). Length-frequency distribution (LFD) for E. viator showed a bimodal distribution typical for long-lived species and a sexual dimorphism with females significantly longer than males. Although the stability of LFD through years seems to rule out the possibility of E. viator to be at risk in the Kerguelen EEZ, further studies must be conducted to assess population size and mitigate shark by-catch in the French longline fisheries.