Depletion of trophy large-sized sharks populations of the south-western Atlantic: insights from fishers knowledge

ALEJO J. IRIGOYEN; GASTON TROBBIANI

NEOTROPICAL ICHTHYOLOGY

SOC BRASILEIRA ICTIOLOGIA

Lugar: Porto Alegre; Año: 2016 vol. 14

1679-6225

Globally, sharks are impacted by a wide range of human activities, resulting in many populations being depleted. Trophy large-sized sharks of the south west Atlantic, the sand-tiger Carcharias taurus, the copper Carcharhinus brachyurus and the broadnose sevengill shark Notorynchus cepedianus are under intense sport and artisanal fishing since the 50?s decade. However, there is no current or historical information for the assessment of its populations status. Expert fishermen knowledge (FK), gathered on this work on semi-structured interviews, about abundance variation between the beginning and the end of their fishing careers revealed a critical status for the species study (means variation between -77 and -90 %). Furthermore, a best day´s catch analysis reinforce this result in the case of the sand tiger shark. The school shark Galeorhinus galeus was included on this work with the objective of contrast FK with formal information available of catch-per-unit-effort (CPUE) time series. Both sources of information, despite are not comparable, shows declines ~ - 80%. Additionally, information about seasonal occurrence of adults and neonates, gathered on this work provide more specific information of potential key nursery and birth areas. The critical conservation situation of study species needs urgent management action.