HAL (Le Centre pour la Communication Scientifique Directe), Mar 27, 2018
National audienceDans le cadre des suivis pluriannuels des communautés piscicoles d'eau coura... more National audienceDans le cadre des suivis pluriannuels des communautés piscicoles d'eau courante, la quantification et la taille des juvéniles de l'année sont le plus souvent obtenues lors d'une unique campagne d'échantillonnage automnale. Au regard de la plasticité de croissance des poissons et de leurs réponses aux différents facteurs environnementaux, comme la température et l'hydrologie, les individus d'une même classe d'âge présentent une importante variabilité de taille. C'est pourquoi l'observation des conditions environnementales sur la croissance nécessite une estimation précise de l'âge des individus à l'aide des outils otolithométriques. Cette étude réalisée sur le Bas-Rhône médian et consacrée au chevaine (Cyprinidae, Squalius cephalus) a pour but de caractériser la variabilité spatio-temporelle de la forme et des taux de croissance journaliers des otolithes des juvéniles d'âge 0+. Les individus ont été échantillonnés dans trois sections distinctes du bief de Caderousse : le canal de fuite de l'usine de Bollène, une section court-circuitée et la retenue de l'usine de Caderousse. Nous avons comparé les résultats obtenus lors de deux années, 2013 et 2015, afin d'évaluer les effets de la température, des débits et de la date d'éclosion sur les taux de croissance journaliers. Tout d'abord, la forme des otolithes a été étudiée afin de déterminer si les individus se déplaçaient entre les différents sites d'étude. La forte discrimination de la forme des otolithes entre les sites observables chaque année suggère une sédentarité dans les sites et une structuration conservée dans le temps, mais la variabilité interannuelle des conditions hydroclimatiques influence significativement la forme des otolithes. Les taux de croissance ont été plus élevés en 2015 qu'en 2013 mais les profils interannuels des courbes de croissance ont été similaires avec un plus fort taux de croissance dans le canal de fuite par rapport à la retenue et à la section court-circuitée. Ces résultats suggèrent une influence prépondérante des conditions du milieu sur la forme et la croissance des otolithes. Les estimations de l'âge ont été utilisées pour rétro-calculer les dates d'éclosion de l'ensemble des individus étudiés. Plusieurs cohortes ont été identifiées chaque année, confirmant la stratégie de pontes multiples des chevaines. En 2015, la période d'éclosion (avril à juin) a été plus courte qu'en 2013 (avril à août). Ces différences ont été attribuées aux régimes hydrologiques et thermiques contrastés entre les deux années
The present study describes the otolith shape and age of three species of Gobiidae: Neogobius mel... more The present study describes the otolith shape and age of three species of Gobiidae: Neogobius melanostomus (Pallas, 1814), Ponticola eurycephalus (Kessler, 1974) and Mesogobius batrachocephalus (Pallas, 1814) from the Western part of the Black Sea. These phylogenetically close species showed otolith shape differences. The round goby, Neogobius melanostomus, showed differences in otolith shape between local populations, probably related to differences in diet and environmental variability influenced by the Danube River inputs in the North of the study area. The age of these commercially exploited species was estimated by otolith microstructural analysis and the results were linked to sex, size and weight. This information is valuable for fishery management purposes.
Long-term surveys confirm the rapidity of environmental and biological changes undergone by endan... more Long-term surveys confirm the rapidity of environmental and biological changes undergone by endangered species but that also concerned relatively “tolerant” species, especially common rheophilic species such as European chub (Squalius cephalus, Linnaeus 1758). As many organisms, fish are highly vulnerable during their first life stages. Body size is a determinant factor for ecosystem functioning and for fish to survive to predators or to winter conditions. While numerous studies has already demonstrated the large variability of autumnal size of fish hatched during the year, few have focused on the factors explaining these interannual variations and on the growth patterns underlying these distributions. Using otoliths of young-of-the-year (YOY), we studied how the interannual variability in fall sizes of chub might be related to varying phenology, temperature, hydrology and growth patterns. YOY were sampled in three sections of the same reach of the Rhône River with contrasted hydrol...
Le corb, Sciaena umbra, est une espece longevive a croissance lente tres convoitee par les chasse... more Le corb, Sciaena umbra, est une espece longevive a croissance lente tres convoitee par les chasseurs sous-marins. Cette pression de chasse a contribue a la diminution des effectifs et a une rarefaction des individus de grande taille hors des reserves marines. En 2014, en reponse a ce declin, un moratoire de cinq ans a ete mis en place pour proteger cette espece sur les cotes francaises. Dans cette etude, l’âge d’une grande femelle braconnee dans la reserve marine de Scandola a ete estime a 31 ans, ce qui est l’âge le plus eleve trouve a ce jour dans la bibliographie pour cette espece.
Despite the interest of studying animal populations at the limit of their geographical distributi... more Despite the interest of studying animal populations at the limit of their geographical distribution, little is known about the shag (Phalacrocorax aristotelis) in the extreme southern part of its range. In this study, the diet of the Mediterranean shag subspecies (P. a. desmarestii) was studied in the Riou Archipelago (French Mediterranean coast) through the analysis of 109 regurgitation pellets during the non-breeding period from 2004 to 2007. The objectives were (i) to determine the diet of the shag in this area, and (ii) to evaluate the interaction with local fisheries. A total of 2462 pairs of otoliths was found in pellets. Six fish families (Atherinidae, Pomacentridae, Labridae, Centracanthidae, Sparidae and Serranidae) composed 92 % of the shag diet (prey number). Shags mainly fish on shallow rocky bottoms and above or in Posidonia oceanica seagrass meadows. As they mainly targeted small fishes (∼10 cm TL), they did not strongly overlap with local fishing activities. Moreover,...
The diet of shag Phalacrocorax aristotelis desmarestii was studied in a NW Mediterranean archipel... more The diet of shag Phalacrocorax aristotelis desmarestii was studied in a NW Mediterranean archipelago (Marseilles, France) through the analysis of 109 regurgitation pellets during the non-breeding period (April to September) from 2004 to 2007. A total of 2 462 pairs of fish otoliths was found in pellets. These fishes belong to 12 families and 25 species. Six fish families (Atherinidae, Pomacentridae, Labridae, Centracanthidae, Sparidae and Serranidae) composed 92% of the shag diet. The diet remained stable during the four year study, but monthly variations were detected. These variations could result from diet changes at the end of the chick rearing period or from seasonal changes of fish community composition. The depth at which shags caught their prey was also determined. Shags mainly fish above or in Posidonia oceanica seagrass meadows, and mainly targeted small fishes (~10 cm TL). The mean fish biomass eaten daily by shag (280 g) was lower than that consumed by this species in th...
La sole commune presente au cours de son cycle de vie un changement ontogenetique d’habitat. Les ... more La sole commune presente au cours de son cycle de vie un changement ontogenetique d’habitat. Les larves sont marines et pelagiques, les juveniles sont benthiques et vivent dans les nourriceries cotieres (lagunes et estuaires) alors que les adultes sont benthiques et marins en zones plus profondes. Les otolithes sont des concretions mineralisees de carbonate de calcium de l’oreille interne des teleosteens qui ne subissent ni dissolution ni resorption. Ils enregistrent les caracteristiques chimiques et isotopiques des milieux traverses.L’etude de la croissance, de la composition chimique et isotopique des otolithes des soles des nourriceries a confirme l’existence de deux stocks de soles dans le golfe du Lion, un a l’Est et l’autre a l’Ouest. Les faibles valeurs de 13C et les fortes valeurs de Ba/Ca des otolithes des soles de l’Est du golfe ont ete associees a une forte influence des apports rhodaniens sur la phase de vie larvaire lors des annees ou le debit du Rhone est normal. En p...
Stable isotope ratios in muscle (C, N) and otolith (C, O), and otolith microchemistry were analys... more Stable isotope ratios in muscle (C, N) and otolith (C, O), and otolith microchemistry were analysed in common soles when they entered a coastal lagoon in spring and when they returned to the sea in autumn. Fingerprints of lagoonal life were observed both in muscle and otolith, but were fixed for the whole life of fish in otoliths only.
Abstract Trait‐based approaches are increasingly used to study species assemblages and understand... more Abstract Trait‐based approaches are increasingly used to study species assemblages and understand ecosystem functioning. The strength of these approaches lies in the appropriate choice of functional traits that relate to the functions of interest. However, trait–function relationships are often supported by weak empirical evidence. Processes related to digestion and nutrient assimilation are particularly challenging to integrate into trait‐based approaches. In fishes, intestinal length is commonly used to describe these functions. Although there is broad consensus concerning the relationship between fish intestinal length and diet, evolutionary and environmental forces have shaped a diversity of intestinal morphologies that is not captured by length alone. Focusing on coral reef fishes, we investigate how evolutionary history and ecology shape intestinal morphology. Using a large dataset encompassing 142 species across 31 families collected in French Polynesia, we test how phylogeny, body morphology, and diet relate to three intestinal morphological traits: intestinal length, diameter, and surface area. We demonstrate that phylogeny, body morphology, and trophic level explain most of the interspecific variability in fish intestinal morphology. Despite the high degree of phylogenetic conservatism, taxonomically unrelated herbivorous fishes exhibit similar intestinal morphology due to adaptive convergent evolution. Furthermore, we show that stomachless, durophagous species have the widest intestines to compensate for the lack of a stomach and allow passage of relatively large undigested food particles. Rather than traditionally applied metrics of intestinal length, intestinal surface area may be the most appropriate trait to characterize intestinal morphology in functional studies.
BNP Paribas Foundation; Agence National de la Recherche, Grant/Award Number: ANR-17-CE32-0006; U.... more BNP Paribas Foundation; Agence National de la Recherche, Grant/Award Number: ANR-17-CE32-0006; U.S. National Science Foundation, Grant/Award Number: OCE1547952
While otolith shape analysis can provide a valuable tool for discriminating between fish populati... more While otolith shape analysis can provide a valuable tool for discriminating between fish populations, factors which may influence otolith shape, such as the effect of size, directional asymmetry in growth, and local environmental conditions, are often unknown. Here, we analyzed differences in otolith shape across three size classes of age-0 common sole Solea solea L. from nursery grounds off the Belgian coast and in the Wadden Sea. Across size classes, form-factor decreased and roundness remained consistently high in both nursery grounds, while ellipticity increased in the Belgian nursery. Directional asymmetry between left and right otoliths measured by Fourier coefficients accounted for 0.96 and 7.2% of the variance when comparing otoliths overall, and for each size class, respectively. Within the Belgian nursery, results were consistent across sampling years and locations. In addition, otolith shape was marginally different between nursery grounds, but highly variable within nursery grounds. A small divergent group, which seems partly related to fish size, was noted at both spatial and temporal scales. Based on these results and before embarking on a study of population structure using otolith shape in age-0 common sole, we recommend testing for directional asymmetry and fish size effects across the entire region of interest.
This assesses features of otoliths from laboratory-reared embryos, larvae and juvenile European c... more This assesses features of otoliths from laboratory-reared embryos, larvae and juvenile European chub Squalius cephalus from hatching to 180 days post-hatching (dph). We observed the development of the three pairs of otoliths (lapilli, sagittae and asterisci) and more precisely shape changes, as well as timing and deposition rate of increments of the lapilli. The lapilli and the sagittae were present at hatching, whereas the asterisci formed between 20 and 30 dph. The lapillus and sagitta shapes were round until 20 dph. From 60 dph the anterior and the posterior rostra of the sagittae were well developed, but very thin, making this otolith too fragile to manipulate for further studies of shape and validation of otolith increment deposition rate. The lapilli provided reliable age estimates for free embryos, larvae and juveniles up to 120 dph. However, caution should be taken when ageing fish older than 150 dph as an underestimation was noticeable. The regression of the number of otolith increments on age showed a slope and an intercept not significantly different from 1 and 0, respectively, which indicated that otolith growth increments were deposited on a daily basis, with the first microincrement occurring at hatching. Increment counts were consistent between three interpreters, indicating a consistent and reliable age estimate. This study validates that the otolith increment deposition rate can be used to assess hatching dates and daily growth of wild S. cephalus under 150 dph and in environments similar to the conditions used in this study.
This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus ... more This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus uses different habitats throughout its life (mainly juvenile and adult phases). Of the most informative trace elements within otoliths (the twelve isotopes 23 Na, 25 Mg, 43 Ca, 55 Mn, 59 Co, 60 Ni, 63 Cu, 66 Zn, 86 Sr, 111 Cd, 138 Ba and 208 Pb) only three ratios of Ca (Na:Ca, Sr:Ca and Ba:Ca) were informative and therefore used in a multivariate regression-tree analysis. Using a multivariate partitioning, three main phases were described from profiles, including the larval life phase (leptocephali), the intermediate phase (longest section between the larval life phase and the terminal phase) and the terminal phase (final section i.e., the most recent months preceding the death of fish). According to concentrations of the three ratios to Ca, G. chilospilus can be separated into three groups during their larval life stage (very different in Sr and Na), four groups during the intermediate phase (few differences in Sr and Na) and three groups during the terminal phase (differences in Sr), illustrating that G. chilospilus inhabit different habitats during these three phases. Our results showed that the leptocephali encountered different oceanic water masses with fluctuating Sr:Ca ratios during the early larval phase. During the intermediate phase (main part of their life-span), they lived in lagoonal waters such as fringing reefs or reef flats of lagoonal islets, characterized by a lower Sr:Ca ratio. During the latter part of their life, approximately one third of G. chilospilus encountered more oceanic waters close to or at barrier reefs, suggesting possible movements of these fish along a coast-to-ocean gradient.
HAL (Le Centre pour la Communication Scientifique Directe), Mar 27, 2018
National audienceDans le cadre des suivis pluriannuels des communautés piscicoles d'eau coura... more National audienceDans le cadre des suivis pluriannuels des communautés piscicoles d'eau courante, la quantification et la taille des juvéniles de l'année sont le plus souvent obtenues lors d'une unique campagne d'échantillonnage automnale. Au regard de la plasticité de croissance des poissons et de leurs réponses aux différents facteurs environnementaux, comme la température et l'hydrologie, les individus d'une même classe d'âge présentent une importante variabilité de taille. C'est pourquoi l'observation des conditions environnementales sur la croissance nécessite une estimation précise de l'âge des individus à l'aide des outils otolithométriques. Cette étude réalisée sur le Bas-Rhône médian et consacrée au chevaine (Cyprinidae, Squalius cephalus) a pour but de caractériser la variabilité spatio-temporelle de la forme et des taux de croissance journaliers des otolithes des juvéniles d'âge 0+. Les individus ont été échantillonnés dans trois sections distinctes du bief de Caderousse : le canal de fuite de l'usine de Bollène, une section court-circuitée et la retenue de l'usine de Caderousse. Nous avons comparé les résultats obtenus lors de deux années, 2013 et 2015, afin d'évaluer les effets de la température, des débits et de la date d'éclosion sur les taux de croissance journaliers. Tout d'abord, la forme des otolithes a été étudiée afin de déterminer si les individus se déplaçaient entre les différents sites d'étude. La forte discrimination de la forme des otolithes entre les sites observables chaque année suggère une sédentarité dans les sites et une structuration conservée dans le temps, mais la variabilité interannuelle des conditions hydroclimatiques influence significativement la forme des otolithes. Les taux de croissance ont été plus élevés en 2015 qu'en 2013 mais les profils interannuels des courbes de croissance ont été similaires avec un plus fort taux de croissance dans le canal de fuite par rapport à la retenue et à la section court-circuitée. Ces résultats suggèrent une influence prépondérante des conditions du milieu sur la forme et la croissance des otolithes. Les estimations de l'âge ont été utilisées pour rétro-calculer les dates d'éclosion de l'ensemble des individus étudiés. Plusieurs cohortes ont été identifiées chaque année, confirmant la stratégie de pontes multiples des chevaines. En 2015, la période d'éclosion (avril à juin) a été plus courte qu'en 2013 (avril à août). Ces différences ont été attribuées aux régimes hydrologiques et thermiques contrastés entre les deux années
The present study describes the otolith shape and age of three species of Gobiidae: Neogobius mel... more The present study describes the otolith shape and age of three species of Gobiidae: Neogobius melanostomus (Pallas, 1814), Ponticola eurycephalus (Kessler, 1974) and Mesogobius batrachocephalus (Pallas, 1814) from the Western part of the Black Sea. These phylogenetically close species showed otolith shape differences. The round goby, Neogobius melanostomus, showed differences in otolith shape between local populations, probably related to differences in diet and environmental variability influenced by the Danube River inputs in the North of the study area. The age of these commercially exploited species was estimated by otolith microstructural analysis and the results were linked to sex, size and weight. This information is valuable for fishery management purposes.
Long-term surveys confirm the rapidity of environmental and biological changes undergone by endan... more Long-term surveys confirm the rapidity of environmental and biological changes undergone by endangered species but that also concerned relatively “tolerant” species, especially common rheophilic species such as European chub (Squalius cephalus, Linnaeus 1758). As many organisms, fish are highly vulnerable during their first life stages. Body size is a determinant factor for ecosystem functioning and for fish to survive to predators or to winter conditions. While numerous studies has already demonstrated the large variability of autumnal size of fish hatched during the year, few have focused on the factors explaining these interannual variations and on the growth patterns underlying these distributions. Using otoliths of young-of-the-year (YOY), we studied how the interannual variability in fall sizes of chub might be related to varying phenology, temperature, hydrology and growth patterns. YOY were sampled in three sections of the same reach of the Rhône River with contrasted hydrol...
Le corb, Sciaena umbra, est une espece longevive a croissance lente tres convoitee par les chasse... more Le corb, Sciaena umbra, est une espece longevive a croissance lente tres convoitee par les chasseurs sous-marins. Cette pression de chasse a contribue a la diminution des effectifs et a une rarefaction des individus de grande taille hors des reserves marines. En 2014, en reponse a ce declin, un moratoire de cinq ans a ete mis en place pour proteger cette espece sur les cotes francaises. Dans cette etude, l’âge d’une grande femelle braconnee dans la reserve marine de Scandola a ete estime a 31 ans, ce qui est l’âge le plus eleve trouve a ce jour dans la bibliographie pour cette espece.
Despite the interest of studying animal populations at the limit of their geographical distributi... more Despite the interest of studying animal populations at the limit of their geographical distribution, little is known about the shag (Phalacrocorax aristotelis) in the extreme southern part of its range. In this study, the diet of the Mediterranean shag subspecies (P. a. desmarestii) was studied in the Riou Archipelago (French Mediterranean coast) through the analysis of 109 regurgitation pellets during the non-breeding period from 2004 to 2007. The objectives were (i) to determine the diet of the shag in this area, and (ii) to evaluate the interaction with local fisheries. A total of 2462 pairs of otoliths was found in pellets. Six fish families (Atherinidae, Pomacentridae, Labridae, Centracanthidae, Sparidae and Serranidae) composed 92 % of the shag diet (prey number). Shags mainly fish on shallow rocky bottoms and above or in Posidonia oceanica seagrass meadows. As they mainly targeted small fishes (∼10 cm TL), they did not strongly overlap with local fishing activities. Moreover,...
The diet of shag Phalacrocorax aristotelis desmarestii was studied in a NW Mediterranean archipel... more The diet of shag Phalacrocorax aristotelis desmarestii was studied in a NW Mediterranean archipelago (Marseilles, France) through the analysis of 109 regurgitation pellets during the non-breeding period (April to September) from 2004 to 2007. A total of 2 462 pairs of fish otoliths was found in pellets. These fishes belong to 12 families and 25 species. Six fish families (Atherinidae, Pomacentridae, Labridae, Centracanthidae, Sparidae and Serranidae) composed 92% of the shag diet. The diet remained stable during the four year study, but monthly variations were detected. These variations could result from diet changes at the end of the chick rearing period or from seasonal changes of fish community composition. The depth at which shags caught their prey was also determined. Shags mainly fish above or in Posidonia oceanica seagrass meadows, and mainly targeted small fishes (~10 cm TL). The mean fish biomass eaten daily by shag (280 g) was lower than that consumed by this species in th...
La sole commune presente au cours de son cycle de vie un changement ontogenetique d’habitat. Les ... more La sole commune presente au cours de son cycle de vie un changement ontogenetique d’habitat. Les larves sont marines et pelagiques, les juveniles sont benthiques et vivent dans les nourriceries cotieres (lagunes et estuaires) alors que les adultes sont benthiques et marins en zones plus profondes. Les otolithes sont des concretions mineralisees de carbonate de calcium de l’oreille interne des teleosteens qui ne subissent ni dissolution ni resorption. Ils enregistrent les caracteristiques chimiques et isotopiques des milieux traverses.L’etude de la croissance, de la composition chimique et isotopique des otolithes des soles des nourriceries a confirme l’existence de deux stocks de soles dans le golfe du Lion, un a l’Est et l’autre a l’Ouest. Les faibles valeurs de 13C et les fortes valeurs de Ba/Ca des otolithes des soles de l’Est du golfe ont ete associees a une forte influence des apports rhodaniens sur la phase de vie larvaire lors des annees ou le debit du Rhone est normal. En p...
Stable isotope ratios in muscle (C, N) and otolith (C, O), and otolith microchemistry were analys... more Stable isotope ratios in muscle (C, N) and otolith (C, O), and otolith microchemistry were analysed in common soles when they entered a coastal lagoon in spring and when they returned to the sea in autumn. Fingerprints of lagoonal life were observed both in muscle and otolith, but were fixed for the whole life of fish in otoliths only.
Abstract Trait‐based approaches are increasingly used to study species assemblages and understand... more Abstract Trait‐based approaches are increasingly used to study species assemblages and understand ecosystem functioning. The strength of these approaches lies in the appropriate choice of functional traits that relate to the functions of interest. However, trait–function relationships are often supported by weak empirical evidence. Processes related to digestion and nutrient assimilation are particularly challenging to integrate into trait‐based approaches. In fishes, intestinal length is commonly used to describe these functions. Although there is broad consensus concerning the relationship between fish intestinal length and diet, evolutionary and environmental forces have shaped a diversity of intestinal morphologies that is not captured by length alone. Focusing on coral reef fishes, we investigate how evolutionary history and ecology shape intestinal morphology. Using a large dataset encompassing 142 species across 31 families collected in French Polynesia, we test how phylogeny, body morphology, and diet relate to three intestinal morphological traits: intestinal length, diameter, and surface area. We demonstrate that phylogeny, body morphology, and trophic level explain most of the interspecific variability in fish intestinal morphology. Despite the high degree of phylogenetic conservatism, taxonomically unrelated herbivorous fishes exhibit similar intestinal morphology due to adaptive convergent evolution. Furthermore, we show that stomachless, durophagous species have the widest intestines to compensate for the lack of a stomach and allow passage of relatively large undigested food particles. Rather than traditionally applied metrics of intestinal length, intestinal surface area may be the most appropriate trait to characterize intestinal morphology in functional studies.
BNP Paribas Foundation; Agence National de la Recherche, Grant/Award Number: ANR-17-CE32-0006; U.... more BNP Paribas Foundation; Agence National de la Recherche, Grant/Award Number: ANR-17-CE32-0006; U.S. National Science Foundation, Grant/Award Number: OCE1547952
While otolith shape analysis can provide a valuable tool for discriminating between fish populati... more While otolith shape analysis can provide a valuable tool for discriminating between fish populations, factors which may influence otolith shape, such as the effect of size, directional asymmetry in growth, and local environmental conditions, are often unknown. Here, we analyzed differences in otolith shape across three size classes of age-0 common sole Solea solea L. from nursery grounds off the Belgian coast and in the Wadden Sea. Across size classes, form-factor decreased and roundness remained consistently high in both nursery grounds, while ellipticity increased in the Belgian nursery. Directional asymmetry between left and right otoliths measured by Fourier coefficients accounted for 0.96 and 7.2% of the variance when comparing otoliths overall, and for each size class, respectively. Within the Belgian nursery, results were consistent across sampling years and locations. In addition, otolith shape was marginally different between nursery grounds, but highly variable within nursery grounds. A small divergent group, which seems partly related to fish size, was noted at both spatial and temporal scales. Based on these results and before embarking on a study of population structure using otolith shape in age-0 common sole, we recommend testing for directional asymmetry and fish size effects across the entire region of interest.
This assesses features of otoliths from laboratory-reared embryos, larvae and juvenile European c... more This assesses features of otoliths from laboratory-reared embryos, larvae and juvenile European chub Squalius cephalus from hatching to 180 days post-hatching (dph). We observed the development of the three pairs of otoliths (lapilli, sagittae and asterisci) and more precisely shape changes, as well as timing and deposition rate of increments of the lapilli. The lapilli and the sagittae were present at hatching, whereas the asterisci formed between 20 and 30 dph. The lapillus and sagitta shapes were round until 20 dph. From 60 dph the anterior and the posterior rostra of the sagittae were well developed, but very thin, making this otolith too fragile to manipulate for further studies of shape and validation of otolith increment deposition rate. The lapilli provided reliable age estimates for free embryos, larvae and juveniles up to 120 dph. However, caution should be taken when ageing fish older than 150 dph as an underestimation was noticeable. The regression of the number of otolith increments on age showed a slope and an intercept not significantly different from 1 and 0, respectively, which indicated that otolith growth increments were deposited on a daily basis, with the first microincrement occurring at hatching. Increment counts were consistent between three interpreters, indicating a consistent and reliable age estimate. This study validates that the otolith increment deposition rate can be used to assess hatching dates and daily growth of wild S. cephalus under 150 dph and in environments similar to the conditions used in this study.
This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus ... more This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus uses different habitats throughout its life (mainly juvenile and adult phases). Of the most informative trace elements within otoliths (the twelve isotopes 23 Na, 25 Mg, 43 Ca, 55 Mn, 59 Co, 60 Ni, 63 Cu, 66 Zn, 86 Sr, 111 Cd, 138 Ba and 208 Pb) only three ratios of Ca (Na:Ca, Sr:Ca and Ba:Ca) were informative and therefore used in a multivariate regression-tree analysis. Using a multivariate partitioning, three main phases were described from profiles, including the larval life phase (leptocephali), the intermediate phase (longest section between the larval life phase and the terminal phase) and the terminal phase (final section i.e., the most recent months preceding the death of fish). According to concentrations of the three ratios to Ca, G. chilospilus can be separated into three groups during their larval life stage (very different in Sr and Na), four groups during the intermediate phase (few differences in Sr and Na) and three groups during the terminal phase (differences in Sr), illustrating that G. chilospilus inhabit different habitats during these three phases. Our results showed that the leptocephali encountered different oceanic water masses with fluctuating Sr:Ca ratios during the early larval phase. During the intermediate phase (main part of their life-span), they lived in lagoonal waters such as fringing reefs or reef flats of lagoonal islets, characterized by a lower Sr:Ca ratio. During the latter part of their life, approximately one third of G. chilospilus encountered more oceanic waters close to or at barrier reefs, suggesting possible movements of these fish along a coast-to-ocean gradient.
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Papers by Fabien Morat