For the first time, an otolith shape analysis was used to investigate the stocks of saddled bream (Oblada melanura, Linnaeus, 1758) in three fishing zones along the Tunisian coast (Bizerte, Kélibia and Sayada). Otolith shape analysis was used on 30 otoliths for each site, sampled during the spawning period. Using elliptic Fourier descriptors (EFD) the quantization of the shape otolith was investigated by SHAPE and multivariate statistical procedures. Considering the environmental and the genotypic aspects, the preliminary results of the otolith shape analysis showed dissimilarity in silhouette of otoliths of saddled bream stocks collected from the north (Bizerte), the north-east (Kélibia) and the east (Sayada) of the Tunisian coast. Therefore, these three groups could be considered as three sub-units of the Tunisian stock, which should be managed separately.

Coastal lagoons are highly variable environments that may act as hotspots of genetic diversity as a consequence of their ecological role as nursery habitats of marine species with both ecological and fisheries importance. The edible cockle (Cerastoderma edule) is a commercially important shellfish resource inhabiting coastal lagoons in Europe and their fisheries management urgently needs genetic studies to design appropriate strategies to promote the recovery of exploited populations. The aim of this study was to assess the C. edule genetic diversity and population structure at a small geographic scale, inside Ria Formosa coastal lagoon (southern Portugal) using mitochondrial cytochrome oxidase I sequences in six locations. Outcomes pointed to a common pattern of high haplotype diversity and non-significant genetic structuring inside the Ria Formosa lagoon. A high level of gene flow was detected between all localities and the presence of a single stock from a genetic point of view may be considered for fisheries management purposes. The existence of a high number of haplotypes and high values of haplotype diversity of C. edule in Ria Formosa lagoon could be consistent with the hypothesis that higher genetic diversity is expected in populations occurring in coastal lagoons, suggesting that lagoons could increase standing genetic variation and an adaptive potential of lagoon populations as an ecological response to a highly variable environment.

L'étude des carnets de pêche des marins-pêcheurs et l'échantillonnage des captures ont permis de cerner les caractéristiques biologiques des populations de grandes aloses (Alosa alosa L.) prélevées sur l'Adour de 1988 à 1991 et d'étudier l'influence des conditions hydroclimatiques sur le niveau moyen des captures journalières par sortie. Les aloses sont principalement recrutées dans l'estuaire entre le début du mois d'avril et la fin du mois de mai: entre 78 et 89 % selon les années. Les mâles sont en moyenne plus jeunes et à âge égal plus petits et moins lourds que les femelles. Ces résultats confortent les connaissances obtenues sur les principaux stocks français qui remontent les systèmes fluviaux de la Loire et de la Gironde. Les analyses effectuées soit par l'Analyse Factorielle des Correspondances soit par l'utilisation du Modèle Linéaire Généralisé indiquent que les variations conjuguées du débit fluvial et du coefficient de marée ont une influence sur l'abondance des captures journalières exprimées en kg par sortie. Le travail réalisé à l'aide de ces deux méthodes complémentaires d'analyse permet à la fois de décrire et de quantifier les liens entre les captures par sortie (CPUE) et les facteurs hydroclimatiques. En effet, une augmentation de ces CPUE est constatée avec l'accroissement des coefficients de marée, le débit fluvial intervenant comme facteur de modulation secondaire.

Different random samplings were used to assess the biomass of intertidal bivalves on two main biotopes of the south west coast of New Caledonia. Over the 46.5 km line of sandy beach, the total bivalve biomass is 4.3 ± 1.8 t and the mean biomass of Atactodea striata is about 3.2 ± 1.2 t. Over the 9.85 km2 sandy-muddy shore of the study area, bivalve stocks (1.050 ± 392 t) are dominated by Gafrarium tumidum and Anadara scapha; their mean biomasses are respectively 270 ± 132 t and 418 ± 308 t. This resource is expected to meet the demand of the domestic market through an artisanal fishery.