Life history and connectivity between essential ecological habitats of coastal fishes in temperate seas: case of sandeels species (Ammodytidae) and Sea bass (Dicentrarchus labrax, Linnaeus, 1758) in the Normand Breon Gulf, environmental tracers

• Main Author: LAUGIER, FLORA
• Other Authors: Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU), Muséum national d'Histoire Naturelle (Paris, France), Eric Feunteun, Alexandre Carpentier
• Format: Thesis
• Language: English
• Published: HAL CCSD 2015
• Subjects: Life traits; Connectivity between Essential Habitats; sclerochronology and otolith microchemistry; food webs; stable isotopes; Traits de vie; connectivité entre habitats écologiques essentiels; sclérochronologie et microchimie des otolithes; réseaux trophiques; isotopes stables; envir; geo; Hyperoplus lanceolatus
• Online Access: https://hal.archives-ouvertes.fr/tel-01540497/file/Th%C3%A8se%20Flora%20Laugier%20pour%20diffusion%20finale.pdf; https://hal.archives-ouvertes.fr/tel-01540497

The objectives of our thesis were to precise the use strategies of essential ecological habitats by coastal fishes in the West French Channel (Norman-Breton Gulf and Lannion bay) using life traits for two taxa with contrasted biological cycles. European seabass (Dicentrarchus labrax) serves asmodel of migratory species with long lifespan and the four Ammodytidae sympatric species represent resident species with short lifespan (Ammodytes tobianus, Hyperoplus immaculatus, Hyperoplus lanceolatus et Gymnammodytes semisquamatus). For this purpose, a combination of complementary lifetraits and environmental tracers was used such as individual functional traits (e.g morpho-anatomical features), growth rates calculated via the otolith microstructure, carbon and nitrogen stable isotopes and otolith microchemistry analysis through a continuous laser ablation. In a first part, the combined use of these methods and the monitoring of sandeel species recruitment on each sites of capture highlighted strong interspecific differences of subtidal and intertidal habitat use allowing the cohabitation within the community. More precisely, the two Hyperoplus species could inhabit different sandy habitats duringtheir lifecycle as subtidal habitats at the adult stage whereas G. semisquamatus and A. tobianus seem to stay all their life in subtidal and intertidal habitats respectively. In a second part, for the case of the European seabass, the microchemistry and microstructure study and more precisely Sr/Ba variation alongthe otolith axis from the center to the otolith edge indicated a marine larval migration followed by a postlarval arrival in brackish waters, proving a coastal recruitment. Then during the juvenile growth, different life histories were detected within and between sites of capture: some individuals spending time in marine waters and others in more coastal waters with variable salinities. Moreover, the stable isotopes analysis and the functional traits associated to the locomotion and food acquisition corroborate the ...