Data/hora: 27/07/2024 03:03:50

Provedor de dados: 	Institutional Archive of Ifreme (ArchiMer)	
País: 	France	
Título: 	Sources de variation de la forme des otolithes: Implications pour la discrimination des stocks de poissons	
Autores: 	Mahe, Kelig.	
Data: 	2019-12-05	
Ano: 	2019	
Palavras-chave: 	Otolithe; Forme; Stock halieutique; Descripteurs de Fourier; Température; Acides gras; Asymétrie directionnelle; Degrés-jours de croissance; Otolith; Shape; Fish stock; Fourier descriptors; Temperature; Fatty acids; Directional asymmetry; Growing degree days.	
Resumo: 	The assessment and management of fish populations is based on the use of management units called fish stocks. The shape of otoliths, calcified structures of the fish's inner ear, can be used to discriminate these stocks. First, this thesis focuses on the study of the spatio-temporal variability of the otolith’s shape for three fish species with different ecological characteristics (size, swimming speed, behaviour in the water column, etc.) and biogeographical environments. The results showed that there is a decreasing structural gradient across stock sizes from large pelagic species to more localised demersal species. This is linked to the fact that some demersal species such as the bogue (Boops boops) are constrained by the presence of geographical barriers and hydrological fronts, which is not the case for the analysed pelagic species (blue whiting, Micromesistius poutassou; swordfish, Xiphias gladius). Secondly, we tested the effects of potential confounding factors (e. g. bilateral directional asymmetry, DA) on the discriminating power of an otolith’s shape. We have shown that there is a DA for bogue, induced by the lateralisation process, which varies in amplitude and direction according to the geographical area. In the bogue, this DA impacts stock identification by otolith shape, which changes according to which otolith is used (i.e. right or left). Otolith shape is useful to discriminate among fish stocks because it reflects the specific environmental conditions that fish have experienced during their lifetime. Finally, in the third part of the thesis, we analyzed, under controlled conditions, the effects of temperature and the diet content of omega-3 polyunsaturated fatty acids (n-3 PUFAs) on otolith morphogenesis for seabass (Dicentrachus labrax). After emergence, two phases can be distinguished in the ontogenesis of otolith shape with an initial elongation that reflects slower growth of the dorso-ventral axis compared to the antero-posterior axis. This leads to more localized modifications, in particular, in a more complex area between the rostrum and the anti-rostrum, which is clearly linked to the thermal regime. Conversely, the percentage of n-3 PUFAs does not appear to influence otolith morphogenesis. The use of growing degree days (GDD) has shown that the effect of temperature is to accelerate morphogenesis, but also to change its trajectory: at a fixed GDD value, for two given temperatures, the shapes differ. All the results obtained in this thesis validate the use of the otolith shape to discriminate fish stocks, but also emphasize the need to know the precise sources of morphological variability of intra-stock otoliths in order to determine more precisely the limits of fish stocks.	
Tipo: 	Text	
Idioma: 	Francês	
Identificador: 	https://archimer.ifremer.fr/doc/00598/70972/69201.pdf

https://archimer.ifremer.fr/doc/00598/70972/	
Editor: 	Université du Littoral Cote d'Opale	
Formato: 	application/pdf	
Fonte: 	info:eu-repo/semantics/openAccess

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