… diverses populations: adaptations comportementales …

Pbrehmer

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… diverses populations: adaptations comportementales …

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• Publié par: umoryhel
• Nombre de lectures: 118
• Langue: Français

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THESE (PhD)

Présentée devant L’Ecole Nationale Supérieure Agronomique de Rennes

pour obtenir le titre de docteur de l’Ensar

Spécialité: HALIEUTIQUE

par

Patrice Brehmer

«

Analyse comparée des caractéristiques dynamiques et spatiales des bancs de

Sardinella

aurita

(Valenciennes, 1847) de diverses populations: adaptations comportementales face à

l’environnent et à l’exploitation ; effet sur la capturabilité

»

Directeur: François Gerlotto (IRD, Valparaiso)

Rapporteur: Thang DoChi (CNRS-Université de Montpellier II, Montpellier)

Rapporteur: Jacques Sacchi (Ifremer, Sète)

Examinateur: Andrew Bakun (Université de Miami, Floride)

Examinateur: Didier Gascuel (Ensar, Rennes)

Examinateur: Denis Reale (Univsersité du Québec, Montréal)

Examinateur: Jean Guillard (INRA, Thonon-les-bains)

Abstract

The behaviour of fish school, functional unit on which the fishing pressure focus in general, is

the major source of bias of the biomass index obtained by the methods of stock assessment

(echo-integration, scientific fishing etc..). This work, want to measure the possible relation

between the fishing effort and the fish school avoidance reaction. In this goal, we have made a

comparative approach from three genetically independent stock of

Sardinella aurita

, with a

similar environment but a different historical fishing exploitation. The avoidance behaviour

generated by the boat perception (acoustic, visual and tactile), can be measured by the

in situ

school kinematic. We have developed

Infobancs

software for the exploitation of

omnidirectional sonar data and an observation methodology, considering the boat in cruise or

in drift. The environment, (biotic, abiotic) and the intrinsic characteristics of the population

have a direct impact on this behaviour, which is expressed by morphological deformation and

three distinct wave of avoidance. We present the hypothesis of a innate of acquired of the

avoidance reaction. Our results show for a same fishing effort, catches more important in

Venezuela than in Senegal and Ivory Coast. More over the spatial and kinematics

in situ

observations of school show an avoidance behaviour different in Venezuela, in front of the

two Africans stocks. This indicate the existence of a link between fishing effort and the

avoidance, and so the adaptative response to the fishing pressure. This behavioural adaptation

comes from a Darwin selection process and/or a learning of the

Sardinella aurita

populations

to the fishing exploitation. In order to measure the bias engendered by the avoidance on the

stock management, we discuss of the conception of virtual fish school and the possibilities of

a continuous three-dimensional recording of the avoidance reaction.