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Sagittal otoliths of the yellowstripe goatfish Mulloidichthys flavolineatus were analysed in order to compare Reunion Island fish stocks with those of Mauritius (south-west Indian Ocean). Conventional otolith morphometric variables (area, perimeter, length and width), shape indices (form factor, roundness, circularity, rectangularity, ellipticity and eccentricity) and Fourier shape analysis were compared between three sites; two in Reunion Island and one in Mauritius. Regional and site-specific differences were found for all the conventional otolith morphometric features. Regarding the shape indices, the differences between sites were best described by form factor, roundness, circularity and rectangularity. A classification by canonical discriminant analysis indicated significant differences between the three sampling sites. The combined use of morphometric variables (size and shape) and external outlines (shape analysis through Fourier series) showed the importance of otolith shape for intraspecific discrimination.

The 2 amphidromous gobiids Sicyopterus lagocephalus and Cotylopus acutipinnis from La Réunion Island (Mascarene archipelago, south-western Indian Ocean) are heavily exploited by traditional fisheries during their river colonisation. Traits of their oceanic larval life were investigated to better understand the complex life cycle of these fishes. Age estimates were established using otolith increment counts and an alizarin complexon validation method. Larval duration was longer for the widespread S. lagocephalus (133 to 266 d; mean 199 ± 33 d) than for the endemic C. acutipinnis (78 to 150 d; mean 101 ± 14 d), which reflects their distributional ranges. For both species, no correlation was established between age and size, suggesting a decrease in growth during the larval phase. From the back-calculated birth dates, all S. lagocephalus of a major colonisation episode (December 2002) were hatched during the cool season. All results are discussed in terms of the recruitment origins of S. lagocephalus and C. acutipinnis within the Mascarenes. Recognition of the differences in larval life traits is essential for proposing both management and conservation measures for each species.

Anguillid glass eels were sampled between October 2000 and October 2001 in an estuarine goby-fry traditional fishery of Réunion Island (21°S, 56°E), Mascarene Islands, western Indian Ocean. Recruitment occurred from November to April. Among the 633 specimens collected, 4 species were identified by biometric measurements coupled with number of vertebrae (61.9% of the specimens were Anguilla marmorata, 19.4% A. bicolor bicolor, 18.3% A. mossambica and 0.3% A. nebulosa labiata). A. mossambica had the shortest total length at recruitment (51.2 ± 2.7 mm), compared to A. marmorata (53.3 ± 2.5 mm) and A. bicolor bicolor (54.0 ± 2.1 mm). Most juvenile pigmentation corresponded to the glass eel stage (VA to VB). We extracted 34 otoliths and visualized their microstructure by SEM. The short-finned A. bicolor bicolor had the shortest leptocephalus stage (46.2 ± 5.8 d) and age at recruitment (79.8 ± 7.7 d). The long-finned glass eels had the same age at recruitment (120.2 ± 24.7 and 123.6 ± 17 d for A. marmorata and A. mossambica respectively) and the same leptocephalus stage duration (96.9 ± 26.4 and 102.1 ± 17.2 d for A. marmorata and A. mossambica respectively). Otolith readings and sampling dates showed that A. mossambica hatched about 2 mo earlier than A. marmorata. Their identical early life histories should imply adjoining spawning grounds, whereas A. bicolor bicolor must spawn in a distinctive location. Hypotheses for spawning area locations are discussed as a function of the region's oceanic circulation.

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Much concern has been raised about the decline in the European eel (Anguilla anguilla) population. European management plans for the recovery of the stock are now in preparation, the main objective being to increase the escapement of the potential spawners (silver eels) in each basin to allow 40% of the pristine biomass to escape. However, there are relatively few studies on silver eel escapement and production, and no recent measurement of escapement in lagoons, habitats which support large silver eel sub-populations in the Mediterranean region. A markrecapture study was carried out in autumn 2007 in order to estimate the number of silver eels migrating from the Bages-Sigean lagoon in the SouthWest of France. The migrating population, mostly males between 36 and 42 cm, was estimated to be around 1 120 000 eels (30 kg·ha -1 ). The exploitation rate by professional fishermen was around 20% (6 kg·ha -1 ), leading to an escapement level of 80% (24 kg·ha -1 ). The results are discussed regarding the available data in the literature on silver eel escapement. RÉSUMÉTaille et échappement de la population d'anguilles argentées d'une lagune méditerranéenne : Bages-Sigean, FranceLe déclin de l'anguille européenne Anguilla anguilla est très préoccupant et chaque pays européen a maintenant le devoir de préparer un plan de gestion pour la reconstitution du stock. Le principal objectif est d'assurer un taux d'échappement d'au moins 40 % de la biomasse pristine des anguilles argentées (futurs géniteurs) vers leur lieu de reproduction. Cependant, très peu de recherches ont été menées sur l'estimation du stock et du taux d'échappement des anguilles argentées et aucune estimation récente du taux d'échappement n'avait encore été réalisée en Méditerranée. Cette étude de marquage-recapture a été réalisée en automne 2007 dans le but d'estimer la quantité d'anguilles argentées migrantes de la lagune de Bages-Sigean. La population migrante, principalement des mâles entre 36 et 42 cm, a été estimée à 1 120 000 anguilles (30 kg·ha -1 ). Le taux d'exploitation par les pêcheurs professionnels évalué à 20 % (6 kg·ha -1 ) laisse suggérer un taux d'échappement de 80 % (24 kg·ha -1 ). Les résultats sont discutés au regard de la littérature disponible sur l'échappement des anguilles argentées.

Otolith shape analysis has been used in a number of studies as an inexpensive and powerful method for categorising fish in individual stocks. Elliptical Fourier analysis was used on three different amphidromous Sicyopterus species. Sicyopterus lagocephalus is a widespread species while the other two have a limited distribution area, Sicyopterus aiensis being endemic to Vanuatu, and Sicyopterus sarasini to New Caledonia. Both endemics live in sympatry with the widespread species. The otolith shape of all fish sampled was a clear species differentiator, thereby demonstrating that otolith shape is species-specific. At an intraspecific level there are different river populations within samples from Vanuatu, indicating a western group and an eastern "central" group.These results are congruent both for the endemic species, S. aiensis and for the cosmopolitan species. Finally, we found that, for S. lagocephalus, the cosmopolitan species, New Caledonian samples are close to western Vanuatu samples, the latter two being well differentiated from the eastern "central" Vanuatu samples. The explanation for these results may lay either in the influence of environmental factors on the otolith shape, or in the influence of common early life history thus reflecting genetic factors, or a combination of both.