Éditeur(s) : HAL CCSD Laboratoire Arago
Résumé : International audience
As it is unlikely that successful settlement is solely a matter of chance (i.e. tofind a suitable habitat), one of the greatest challenges facing the fish larvae is how to locate therelatively rare patches of coral reef habitat on which they settle and ultimately reside as adults.The answer must lie partly in the sensory modalities of fishes at settlement. Habitat selection isonly possible if fish larvae could detect some environmental cues to select a suitable reef habitatat settlement. The present review aims at providing the latest works dealing with informationperception in coral reef fish larvae at settlement. Two decades ago, it was generally assumedthat larval behaviors and sensory abilities at settlement were considered too feeble to significantlyaffect dispersal outcomes. Several recent studies showed that recognition of suitable reefhabitats by fish larvae at settlement is based on a combination of visual, chemical and acousticcues. The first part of our review shows the main advances in the knowledge of visual, chemicaland acoustic cues used by fish larvae to detect an island, a reef, a micro-habitat, a conspecific orsome predators. The second part of our review deals with the effect of imprinting and/or innatecapabilities. The third part focuses on the different cues used at different scales and underlinessome contradictory results about the distance of transmission and detection of chemical andacoustic cues in coral reefs. Finally, as global and regional environmental changes have stressedcoral reefs to such an extent that they are either destroyed or in decline, the fourth part presentsthe effects of both anthropogenic and environmental stressors on information perception andresponse capacities in coral reef fish larvae. If polluted seawater disrupts the larval abilities tofind a suitable reef habitat, fish larvae may spend more time in the planktonic environment,resulting in increased energetic costs and predation risk, and consequently a lower larval settlement.We hypothesise that as the stability of fish communities is dependent, in part, on the stabilityof social interactions, the disruption of “larvae-habitat relationships” can have major consequencesfor larval settlement into adult population with further repercussions for the ecosystemas a whole. Overall, larval settlement of coral reef fish is an excellent example of the complexityof interactions between an organism and its environment as without perceiving environmentalcues, fish larva would have very little chance of selecting a suitable reef habitat. Moreover,understanding the relationship between reef state and settlement potential will allow managementplanning for the maintenance of coral reefs that are increasingly degraded.
ISSN: 0240-8759

hal-01191776
https://hal-univ-perp.archives-ouvertes.fr/hal-01191776

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Well-designed and effectively managed networks of marine reserves can be effective tools for both fisheries management and biodiversity conservation. Connectivity, the demographic linking of local populations through the dispersal of individuals as larvae, juveniles or adults, is a key ecological factor to consider in marine reserve design, since it has important implications for the persistence of metapopulations and their recovery from disturbance. For marine reserves to protect biodiversity and enhance populations of species in fished areas, they must be able to sustain focal species (particularly fishery species) within their boundaries, and be spaced such that they can function as mutually replenishing networks whilst providing recruitment subsidies to fished areas. Thus the configuration (size, spacing and location) of individual reserves within a network should be informed by larval dispersal and movement patterns of the species for which protection is required. In the past, empirical data regarding larval dispersal and movement patterns of adults and juveniles of many tropical marine species have been unavailable or inaccessible to practitioners responsible for marine reserve design. Recent empirical studies using new technologies have also provided fresh insights into movement patterns of many species and redefined our understanding of connectivity among populations through larval dispersal. Our review of movement patterns of 34 families (210 species) of coral reef fishes demonstrates that movement patterns (home ranges, ontogenetic shifts and spawning migrations) vary among and within species, and are influenced by a range of factors (e.g. size, sex, behaviour, density, habitat characteristics, season, tide and time of day). Some species move <0.1–0.5 km (e.g. damselfishes, butterflyfishes and angelfishes), <0.5–3 km (e.g. most parrotfishes, goatfishes and surgeonfishes) or 3–10 km (e.g. large parrotfishes and wrasses), while others move tens to hundreds (e.g. some groupers, emperors, snappers and jacks) or thousands of kilometres (e.g. some sharks and tuna). Larval dispersal distances tend to be <5–15 km, and self-recruitment is common. Synthesising this information allows us, for the first time, to provide species, specific advice on the size, spacing and location of marine reserves in tropical marine ecosystems to maximise benefits for conservation and fisheries management for a range of taxa. We recommend that: (i) marine reserves should be more than twice the size of the home range of focal species (in all directions), thus marine reserves of various sizes will be required depending on which species require protection, how far they move, and if other effective protection is in place outside reserves; (ii) reserve spacing should be <15 km, with smaller reserves spaced more closely; and (iii) marine reserves should include habitats that are critical to the life history of focal species (e.g. home ranges, nursery grounds, migration corridors and spawning aggregations), and be located to accommodate movement patterns among these. We also provide practical advice for practitioners on how to use this information to design, evaluate and monitor the effectiveness of marine reserve networks within broader ecological, socioeconomic and management contexts.
ISSN: 1464-7931

Droits : http://creativecommons.org/licenses/by-nc-nd/
hal-01334353
https://hal-univ-perp.archives-ouvertes.fr/hal-01334353
https://hal-univ-perp.archives-ouvertes.fr/hal-01334353/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01334353/file/Green_et_al-2015-Biological_Reviews.pdf
DOI : 10.1111/brv.12155

Éditeur(s) : HAL CCSD Wiley/Blackwell
Résumé : International audience
Marine fishes exhibit spectacular phenotypic changes during their ontogeny, and the identification of their early stages is challenging due to the paucity of diagnostic morphological characters at the species level. Meanwhile, the importance of early life stages in dispersal and connectivity has recently experienced an increasing interest in conservation programmes for coral reef fishes. This study aims at assessing the effectiveness of DNA barcoding for the automated identification of coral reef fish larvae through large-scale ecosystemic sampling. Fish larvae were mainly collected using bongo nets and light traps around Moorea between September 2008 and August 2010 in 10 sites distributed in open waters. Fish larvae ranged from 2 to 100 mm of total length, with the most abundant individuals being <5 mm. Among the 505 individuals DNA barcoded, 373 larvae (i.e. 75%) were identified to the species level. A total of 106 species were detected, among which 11 corresponded to pelagic and bathypelagic species, while 95 corresponded to species observed at the adult stage on neighbouring reefs. This study highlights the benefits and pitfalls of using standardized molecular systems for species identification and illustrates the new possibilities enabled by DNA barcoding for future work on coral reef fish larval ecology.
ISSN: 1755-098X

hal-01342973
https://hal-univ-perp.archives-ouvertes.fr/hal-01342973
DOI : 10.1111/1755-0998.12293

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
In vertebrates, brain functional asymmetries are widespread and increase brain performance. Some species of fishes are known to have brain asymmetries; however, little information is available on brain lateralization in coral reef fishes and the impact this could have during the recruitment phase. In this study, soldierfish, Myripristis pralinia, at the larval and juvenile stage recognized conspecifics through visual cues. Larvae with the ablation of either the right or left telencephalic hemisphere lost the attraction towards conspecific cues. In contrast, juveniles with the ablation of the right (but not left) telencephalic hemisphere still displayed a preference towards conspecific visual cues. These results suggest the left telencephalic hemisphere is responsible for the lateralization process used in the visual recognition of coral reef fish juveniles. The determinism of lateralized perception of conspecifics during fish ontogeny may be a consequence of genetic factors, linked with the metamorphosis processes and/or environmental factors such as predation at recruitment.
ISSN: 0003-3472

hal-01340504
https://hal-univ-perp.archives-ouvertes.fr/hal-01340504
DOI : 10.1016/j.anbehav.2016.04.011

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Lateralization, i.e. the preferential use of one side of the body, may convey fitness benefits for organisms within rapidly-changing environments, by optimizing separate and parallel processing of different information between the two brain hemispheres. In coral reef-fishes, the movement of larvae from planktonic to reef environments (recruitment) represents a major life-history transition. This transition requires larvae to rapidly identify and respond to sensory cues to select a suitable habitat that facilitates survival and growth. This ‘recruitment’ is critical for population persistence and resilience. In aquarium experiments, larval Acanthurus triostegus preferentially used their right-eye to investigate a variety of visual stimuli. Despite this, when held in in situ cages with predators, those larvae that previously favored their left-eye exhibited higher survival. These results support the “brain’s right-hemisphere” theory, which predicts that the right-eye (i.e. left-hemisphere) is used to categorize stimuli while the left-eye (i.e. right-hemisphere) is used to inspect novel items and initiate rapid behavioral-responses. While these experiments confirm that being highly lateralized is ecologically advantageous, exposure to chlorpyrifos, a pesticide often inadvertently added to coral-reef waters, impaired visual-lateralization. This suggests that chemical pollutants could impair the brain function of larval fishes during a critical life-history transition, potentially impacting recruitment success.
ISSN: 2045-2322

Droits : http://creativecommons.org/licenses/by/
hal-01585550
http://hal.upmc.fr/hal-01585550
http://hal.upmc.fr/hal-01585550/document
http://hal.upmc.fr/hal-01585550/file/s41598-017-09381-0.pdf
DOI : 10.1038/s41598-017-09381-0

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades. PAHs are hydrophobic molecules which can accumulate in high concentrations in sediments acting then as major secondary sources. Fish contamination can occur through contact or residence nearby sediments or though dietary exposure. In this study, we analyzed certain physiological traits in unexposed fish (F1) issued from parents (F0) exposed through diet to three PAH mixtures at similar and environmentally relevant concentrations but differing in their compositions. For each mixture, no morphological differences were observed between concentrations. An increase in locomotor activity was observed in larvae issued from fish exposed to the highest concentration of a pyrolytic (PY) mixture. On the contrary, a decrease in locomotor activity was observed in larvae issued from heavy oil mixture (HO). In the case of the third mixture, light oil (LO), a reduction of the diurnal activity was observed during the setup of larval activity. Behavioral disruptions persisted in F1-PY juveniles and in their offspring (F2). Endocrine disruption was analyzed using cyp19a1b:GFP transgenic line and revealed disruptions in PY and LO offspring. Since no PAH metabolites were dosed in larvae, these findings suggest possible underlying mechanisms such as altered parental signaling molecule and/or hormone transferred in the gametes, eventually leading to early imprinting. Taken together, these results indicate that physiological disruptions are observed in offspring of fish exposed to PAH mixtures through diet.
ISSN: 0944-1344

hal-01121865
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01121865
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01121865/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01121865/file/Exposures%20of%20zebrafish_accepted.pdf
DOI : 10.1007/s11356-015-4157-8

Éditeur(s) : HAL CCSD
Résumé : Integrating ecological connectivity into marine ecosystem management and planning is important, especially in a global context of severe fish stocks depletion and growing habitat degradation. Environmental tools such as Marine Protected Areas have been proposed to protect biodiversity, restore damaged ecosystems, sustain fisheries, and rebuild overexploited stocks. The effectiveness of marine protected areas depends in part on the maintenance of connectivity between marine populations, linked by ecological processes such as larval dispersal. In this thesis, we applied a biophysical model driven by ocean currents derived from satellite altimetry to evaluate connectivity between Western Indian Ocean reefs and across the current MPA system in the Mediterranean Sea. We applied different methods of analysis such as graph-theoretic and clustering. In the Western Indian Ocean, marine connectivity analyses show that the number of connections between reefs increases with fish pelagic larval duration. It also highlights a low connectivity across the region and a high interconnectivity within several regions (Mozambique Channel, Mascarene archipelago). In the Mediterranean Sea, connectance is globally low at the regional scale. This connectance is more important in Western than Eastern Mediterranean. Moreover, the marine connectivity analyses revealed high domestic connectivity rates. Depending on the study area, priority reefs or sites for MPA implementation are proposed. Finally, implications for transboundary marine policies and regional cooperation are discussed.
Intégrer les connaissances sur la connectivité écologique dans la gestion des écosystèmes marins est essentiel, surtout dans un contexte d'appauvrissement des ressources marines et de dégradation des habitats côtiers à l'échelle mondiale. Des outils environnementaux, tels que les Aires Marines Protégées ont été mises en œuvre pour protéger la biodiversité, restaurer les écosystèmes endommagés, soutenir les pêcheries et reconstituer les stocks surexploités. Leur efficacité dépend en partie du maintien de la connectivité entre les populations marines, assurée à travers divers processus écologiques dont la dispersion larvaire. Dans le cadre de ce travail de thèse, un modèle biophysique intégrant des données de courants, issues de mesures d'altimétrie par satellite, a été utilisé pour évaluer la connectivité entre les récifs de l'océan Indien d'une part, et à travers le réseau d'AMP de Méditerranée d'autre part. Différentes méthodes d'analyse ont été utilisées, telles que la théorie des graphes et le clustering. Dans l'océan Indien occidental, l'analyse des connectivités marines montre que le nombre de connexions entre les récifs augmente avec la durée de vie larvaire des poissons. Elle met également en évidence une faible connectivité à l'échelle de la région, mais une forte inter-connectivité au sein de plusieurs sous-régions (Canal du Mozambique, Mascareignes). En Méditerranée, la connectance est globalement faible à l'échelle régionale, bien que plus importante dans le bassin occidental que le bassin oriental. L'analyse des connectivités marines montre également un taux de connectivité élevé à l'échelle d'un même pays. Selon le cas d'étude, une liste de récifs ou de sites prioritaires dans la mise en œuvre des AMP a été proposée. Enfin, les implications de ces résultats en termes de politiques transfrontalières et de coopération régionale sont discutées.
https://tel.archives-ouvertes.fr/tel-01269631

NNT : 2015LARE0003
tel-01269631
https://tel.archives-ouvertes.fr/tel-01269631
https://tel.archives-ouvertes.fr/tel-01269631/document
https://tel.archives-ouvertes.fr/tel-01269631/file/2015lare0003_ECrochelet.pdf

Éditeur(s) : Natl Acad Sciences
Résumé : Most marine organisms disperse via ocean currents as larvae, so it is often assumed that larval-stage duration is the primary determinant of geographic range size. However, empirical tests of this relationship have yielded mixed results, and alternative hypotheses have rarely been considered. Here we assess the relative influence of adult and larval-traits on geographic range size using a global dataset encompassing 590 species of tropical reef fishes in 47 families, the largest compilation of such data to date for any marine group. We analyze this database using linear mixed-effect models to control for phylogeny and geographical limits on range size. Our analysis indicates that three adult traits likely to affect the capacity of new colonizers to survive and establish reproductive populations (body size, schooling behavior, and nocturnal activity) are equal or better predictors of geographic range size than pelagic larval duration. We conclude that adult life-history traits that affect the postdispersal persistence of new populations are primary determinants of successful range extension and, consequently, of geographic range size among tropical reef fishes.
Proceedings Of The National Academy Of Sciences Of The United States Of America (0027-8424) (Natl Acad Sciences), 2013-10 , Vol. 110 , N. 41 , P. 16498-16502

Droits : Freely available online through the PNAS open access option.
http://archimer.ifremer.fr/doc/00161/27240/25457.pdf
DOI:10.1073/pnas.1304074110
http://archimer.ifremer.fr/doc/00161/27240/

Résumé : The study conducted in the framework of an agreement between Ifremer and the Local fisheries committee at Audierne is part of a project to restore spiny lobster Palinurus elephas stock levels in the Iroise Sea. It is supported by professional fishermen from Finistère and by the Regional fisheries committee of Brittany. After a brief review of the way lobster stocks are managed worldwide, followed by the major biological and ecological features of red lobster and the state of fisheries in Europe and North Africa, the very poor state of the resource along French coast is borne out by the statistics of landings. Various scenarios (not alternatives) to promote the rebuilding of the biomass are suggested: minimum landing size increase, seasonal closure of the fishery, berried females protection, no fishing zones. The drift of phyllosoma larvae during their long larval stage is addressed using a 3-D hydrodynamic simulation model.
L'étude réalisée dans le cadre d'une convention entre Ifremer et le Comité local des Pêches d'Audierne s'inscrit dans un projet de reconquête des niveaux de ressource en langouste rouge Palinurus elephas en mer d'Iroise soutenu par les pêcheurs professionnels de la pointe du Finistère et par le Comité régional des Pêches de Bretagne. Après avoir rappelé brièvement les modalités de gestion des stocks de langoustes dans le monde puis les grands traits biologiques et écologiques de la langouste rouge et l'état des pêcheries en Europe et dans le nord de l'Afrique, le très mauvais état de cette ressource sur les côtes françaises est confirmé au travers des statistiques de débarquement. Divers scénarios (non alternatifs) visant à favoriser la reconstitution d'une biomasse sont proposés : augmentation de la taille minimale au débarquement, fermeture saisonnière de la pêche, protection des femelles ovigères et création de zones protégées. La dérive des larves phyllosomes au cours de leur longue phase larvaire est abordée par un modèle de simulation hydrodynamique en trois dimensions.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2005/rapport-1198.pdf
http://archimer.ifremer.fr/doc/00000/1198/

Éditeur(s) : Co-tutelle Al Centro de Investigaciones Biológicas del Noroeste - Université de Bretagne occidentale
Résumé : The interest in probiotics for aquaculture is increasing rapidly. In the present work we evaluated the potential of some yeast to induce the larvae gut maturation in sea bass larvae Dicentrarchus labrax. The production of polyamines putrescine, spermidine and spermine was quantified in ten yeast strains using high performance liquid chromatography (HPLC). Afterwards, fluorescently labelled yeast adhesion to the intestine of sea bass larvae and the spotted sand bass (Paralabrax maculatofasciatus) was evaluated by fluorescent microscopy. Two of them, CBS 8339 strain (Debaryomyces hansenii) and X2180 strain (Saccharomyces cerevisiae) produce the polyamines of our interest. The same strains showed the best adhering capabilities to the sea bass and spotted sand bass intestine. Both strains were selected and introduced by pulverization into the diet of larvae. The larvae fed with CBS 8339 strain, increase survival in 8.3% but not in their weight. The secretion of trypsin and amylase as well as those from the brush border membrane: alkaline phosphatase, maltase and leucine aminopeptidase, are incresed at 27 days after hatching (dah). At 42 dah difference in the enzyme activity of the different groups does not exist, suggesting a maturation of the digestive system in early stages of larval development. A second experiment was carried out to know the effect of different levels of incorporation into the diet of CBS 8339 strain: 1.1% and 5.7%. The minimum level, 1.1% of yeast produce best growth and survival rates, as well as lower deformed larvae than those obtained by 5.7% and the control one. Both level of yeast inclusion favored the trypsin secretion and lipase activity at 26 dah. Whereas mRNA levels for trypsin and amylase were influenced by both yeast concentrations at 26 and 36 dah, which suggest a development of digestive capacity of larvae as a result of the presence of polyamines secreted by the yeast.
Les probiotiques ont été définis comme des préparations microbiennes vivantes utilisées comme additif alimentaire, et qui ont une action bénéfique sur l'animal hôte en améliorant la digestion et l'hygiène intestinale. L'application de tels traitements aux productions aquacoles suscite un intérêt qui s'accroît rapidement. Dans ce travail, nous avons étudié l'effet de souches de levures sur la maturation de l'intestin des larves du bar Dicentrarchus labrax. Ces souches produisent des polyamines qui sont impliquées dans la réplication et la différentiation cellulaire, ainsi que dans la synthèse des protéines et des acides nucléiques. Dix souches de levures ont été testées pour leur production de polyamines (putrescine, spermidine et spermine), et pour leur adhérence à la paroi intestinale du bar et la cabrilla (Paralabrax maculatofasciatus). La production des polyamines a été analysée en utilisant la chromatographie liquide à haute performance (HPLC). Les levures selectionées ont été marquées avec un composé fluorescent pour tester leur adhérence a l'intestin de larves de bar et de juvéniles de cabrilla. L'adhérence a pu ainsi être evaluée par observation microscopique en épifluorescence. Les souches CBS 8339 (Debaryomyces hansenii) et X2180 (Saccharomyces cerevisiae) ont été choisies pour leur forte production de spermidine et de spermine, respectivement, et pour leur capacité d'adhérence à l'intestin du bar et de la cabrilla. Les deux souches ont été ajoutées par pulvérisation au régime des larves. Nous avons observé une augmentation de 8.3% du taux de survie avec les larves alimentées avec la souche CBS 8339, mais le poids moyen de ces larves était inférieur à celui obtenu sans ajout de levure. Une augmentation de l'activité de la trypsine et de l'amylase, aussi bien que des activités enzymatiques dans la bordure en brosse, aminopeptidase, phosphatase alkaline et maltase, ont été observées dans les larves âgées de 27 jours alimentées avec la souche CBS 8339. Au jour 42, il n'existait plus de différence d'activité enzymatique entre les larves traitées ou non avec la levure. Ces résultats suggèrent que la maturation du système digestif a été accélérée chez les larves nourries avec la levure, la maturation étant achevée chez les larves de 42 jours, qu'elles aient reçu l'un ou l'autre régime. Une deuxième expérience a été effectuée pour étudier l'effet de différents niveaux d'incorporation dans le régime contenant 1,1% et 5,7% de levure CBS 8339. L'incorporation de 1,1% a induit une augmentation du poids moyen et du taux de survie des larves, ainsi qu'une réduction du taux de malformation de la colonne vertébrale, par rapport aux résultats obtenus avec 0 ou 5,7% de levure. Les deux niveaux d'incorporation de la levure ont favorisé l'activité de la trypsine et de la lipase au jour 26. Les niveaux d'ARNm codant pour la synthèse de la trypsine et de l'amylase ont été influencés par les deux doses de levure aux jours 26 et 36. Ces résultats suggèrent qu'une faible dose de levure améliore le développement et la capacité digestive des larves, et nous formulons l'hypothèse que cette efficacité est due à la production de polyamines in situ. Le rôle des polyamines est particulièrement important pendant les phases de forte croissance comme les stades larvaires, mais elles peuvent être toxiques à dose trop élevée. L'incorporation de levure dans l'aliment destiné aux larves semble donc une excellente méthode pour délivrer les polyamines chez l'animal hôte.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2002/these-103.pdf
http://archimer.ifremer.fr/doc/00000/103/

Éditeur(s) : Elsevier
Résumé : Marine fish larvae undergo major morphological and cellular changes during the first month of life. The ontogeny of the gastrointestinal tract combines these two aspects of the larval development and is very interesting in that the timing of functional changes appears genetically hard-wired. The goal of this paper is to give an overview of the gastrointestinal development process in marine fish larvae, with particular attention to three species: sea bass; red drum; and sole, since the description of gut maturation in fish larvae was initiated during the last decade with these species. During the early stages, marine fish larvae exhibit particular digestive features. Concerning the exocrine pancreas, amylase expression decreases with age from the third week post-hatching in sea bass and red drum (approximately 400 degree days), whereas expression of other enzymes (trypsin, lipase, phospholipase A2...) increases until the end of the larva period. Moreover, secretory function of the exocrine pancreas progressively develops and becomes efficient after the third week of life. Concerning the intestine, enzymes of the enterocyte cytosol (in particular peptidase) have higher activity in young larvae than in older. Approximately in the fourth week of post-hatching development in sea bass, red drum and sole larvae, the cytosolic activities dramatically decline concurrently with a sharp increase in membranous enzyme activities of the brush border, such as alkaline phosphatase, aminopeptidase N, maltase... This process characterises the normal maturation of enterocytes in developing fish larvae and also in other vertebrates' species. The establishment of an efficient brush border membrane digestion represents the adult mode of digestion of enterocytes. This paper also describes the role of diet on the development of the gastrointestinal tract. Indeed, the maturational process of digestive enzyme can be enhanced, stopped, or delayed depending on the composition of the diet.
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology (1532-0456) (Elsevier), 2001-12 , Vol. 130 , N. 4 , P. 477-487

Droits : 2001 Elsevier Science Inc. All rights reserved
http://archimer.ifremer.fr/doc/2001/publication-650.pdf
DOI:10.1016/S1532-0456(01)00274-5
http://archimer.ifremer.fr/doc/00000/650/

Éditeur(s) : Yale University
Résumé : Sea-surface temperature images of the coastal upwelling regions off Northwest Africa show that the core of upwelling is sometimes located far from the coast. This has been documented in three regions that share a common feature, namely a wide and shallow continental shelf. This upwelling feature plays a key role in the ecology of the Canary Current System. It creates an innerfront which provides retention for biological material, e.g. fish eggs and larvae, in the highly productive nearshore environment. An analytical model has been developed based on a two dimensional extension of Ekman's solution. The linear and steady response of a homogeneous ocean forced by an upwelling-favorable wind provides a mechanism for the upwelling separation from the coast. The merging of the surface and bottom Ekman layers induces a very weak cross-shore circulation and a "kinematic barrier" for the Ekman transport divergence. In the case of an alongshore wind, the barrier is located near the isobath h ≈ 0.4D, where D is the thickness of Ekman layers. This yields an upwelling cell which is essentially concentrated in the region 0.5D < h < 1.25D, with upwelling occurring preferentially near the isobath h ≈ 0.6D. It turns out that the cross-shore width of upwelling scales with D/S, the ratio of Ekman depth to bottom topographic slope. The application of this solution to real bathymetric profiles rationalizes, not only the offshore upwelling observations in Northwest Africa, but also the influence of topography on the cross-shelf structure of a wind-driven coastal upwelling. The model also quantifies the effect of the cross-shore wind component showing how it drives the nearshore pressure gradient adjustment and how it affects the upwelling. A linear numerical experiment reproduces the theoretical steady solution, thereby allowing investigation of the transient regime. Relaxation of the hypothesis in the numerical model validates the linear assumption of the theory and then allows investigation of the sensitivity to friction parameterizations and the influence of stratification. The latter leads to an "oscillation" of the upwelling cell with seaward migration driven by outcropping and homogeneization of the water column, and, coastal incursion driven by a "boundary layers splitting" process caused by shoreward advection of the isopycnal dome and stratification of the inner shelf.
Journal of Marine Research (Yale University), 2008-09 , Vol. 66 , N. 5 , P. 589-616

Droits : 2008 Yale University
http://archimer.ifremer.fr/doc/2008/publication-6334.pdf
DOI:10.1357/002224008787536790
http://archimer.ifremer.fr/doc/00000/6334/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Marine organisms are under threat globally from a suite of anthropogenic sources, but the current emphasis on global climate change has deflected the focus from local impacts. While the effect of increased sedimentation on the settlement of coral species is well studied, little is known about the impact on larval fish. Here, the effect of a laterite “red soil” sediment pollutant on settlement behaviour and post-settlement performance of reef fish was tested. In aquarium tests that isolated sensory cues, we found significant olfaction-based avoidance behaviour and disruption of visual cue use in settlement-stage larval fish at 50 mg L−1, a concentration regularly exceeded in situ during rain events. In situ light trap catches showed lower abundance and species richness in the presence of red soil, but were not significantly different due to high variance in the data. Prolonged exposure to red soil produced altered olfactory cue responses, whereby fish in red soil made a likely maladaptive choice for dead coral compared to controls where fish chose live coral. Other significant effects of prolonged exposure included decreased feeding rates and body condition. These effects on fish larvae reared over 5 days occurred in the presence of a minor drop in pH and may be due to the chemical influence of the sediment. Our results show that sediment pollution of coral reefs may have more complex effects on the ability of larval fish to successfully locate suitable habitat than previously thought, as well as impacting on their post-settlement performance and, ultimately, recruitment success.
ISSN: 0029-8549

hal-01270670
https://hal-univ-perp.archives-ouvertes.fr/hal-01270670
DOI : 10.1007/s00442-015-3367-6

Éditeur(s) : Wiley-blackwell Publishing, Inc
Résumé : Oceanic larvae of the European (Anguilla anguilla) and American (A. rostrata) eels have to cross the Atlantic Ocean from the Sargasso Sea to European or North American coasts before entering continental habitats. In some European rivers, eel recruitment is now < 1% of levels in the 1980s. A better understanding of the effects of anthropogenic pressures and environmental fluctuations on eel larvae and subsequent recruitment is a prerequisite to build efficient management plans. The present paper provides insight into the critical oceanic phase of the eel life cycle with a focus on the duration of the larval migration whose estimates varies between 7 months and more than 2 years in both species. Does this range correspond to a natural variability in larval duration or does it stem from methodological artefacts? We first review the different methods used to estimate the duration of larval migration and critically describe their possible sources of misinterpretation. We then evaluate the consistency of these methods with the current knowledge about the ecology and physiology of eel larvae and the physical oceanography. While a moderate discrepancy in migration duration was found between methods for the American eel, the discrepancy was large in the European eel. In this species, otolith microstructure studies indicated migration durations between 7 and 9 months, while other methods pointed to durations of about 2 years. We show that estimates in favour of a long migration duration seem more robust to methodological caveats than methods estimating short durations of migration.
Fish And Fisheries (1467-2960) (Wiley-blackwell Publishing, Inc), 2010-09 , Vol. 11 , N. 3 , P. 289-306

Droits : 2010 Blackwell Publishing Ltd.
http://archimer.ifremer.fr/doc/00011/12208/9033.pdf
DOI:10.1111/j.1467-2979.2010.00362.x
http://archimer.ifremer.fr/doc/00011/12208/

Éditeur(s) : HAL CCSD Linnean Society of London
Résumé : International audience
Although migratory pelagic fishes generally exhibit little geographic differentiation across oceans, as expected from their life-history (broadcast spawning, pelagic larval life, swimming ability of adults) and the assumed homogeneity of the pelagic habitat, exceptions to the rule deserve scrutiny. One such exception is the narrow-barred Spanish mackerel (Scomberomorus commerson), where strong genetic heterogeneity at the regional scale has been previously reported. We investigated the genetic composition of S. commerson across the Indo-West Pacific range using control-region sequences (including previously published datasets), cytochrome-b gene partial sequences, and eight microsatellite loci, to further explore its phylogeographic structure. All haplotypes sampled from the Indo-Malay-Papua archipelago (IMPA) and the southwestern Pacific coalesced into a clade (Clade II) that was deeply separated (14.5% nucleotide divergence) from a clade grouping all haplotypes from the Persian Gulf and Oman Sea (Clade I). Such a high level of genetic divergence suggested the occurrence of two sister-species. Further phylogeographic partition was evident between the western IMPA and the regions sampled east and south of it, i.e. northern Australia, West Papua, and the Coral Sea. Strong allele-frequency differences were found between local populations in the southwestern Pacific, both at the mitochondrial locus (ΦST=0.282-0.609) and at microsatellite loci (^θ=0.202-0.313). Clade II consisted of four deeply divergent subclades (9.0-11.8% nucleotide divergence for the control region; 0.3-2.5% divergence at the cytochrome b locus). Mitochondrial sub-clades within Clade II generally had narrow geographic distribution, demonstrating further genetic isolation. However, one particular haplogroup within Clade II was present throughout the central Indo-West Pacific; that haplogroup was found to be sister-group to an haplogroup restricted to West Papua and the Coral Sea, yielding evidence of recent secondary westward colonization. Such a complex structure is in sharp contrast with the generally weak phylogeographic patterns uncovered to date in other widely distributed, large pelagic fishes with pelagic eggs and larvae. We hypothesize that in S. commerson and possibly other Scomberomorus species, philopatric migration may play a role in maintaining the geographic isolation of populations by annihilating the potential consequences of passive dispersal.
Biological Journal of the Linnean Society

ird-00759711
http://hal.ird.fr/ird-00759711
http://hal.ird.fr/ird-00759711/document

Résumé : This report is presented by Chantal Cahu for obtaining accreditation to supervise research. Since 1981, her research activity has addressed the study of reproducers' nutrition and the young stages of development of marine organisms belonging to two different branch lines, crustaceans and fish. This work, performed in a base-lined research body, IFREMER, is placed within a more general programme of aquaculture development. Indeed, whatever species are at issue, the development of aquaculture in France, as at the global level, is based on the production of juveniles in hatcheries. My work has therefore more precisely the goal of acquiring knowledge about the nutritional needs, mechanisms of digestion and the development of these animals in order to improve the production of prawn post-larvae and fish alevin in the hatchery. This work took place in three main periods that appear in this report: - The study of reproducers' nutrition and its influence on the quality of the Penaeid prawn's eggs and larvae. My work has focused mainly on the effect of lipids and vitamins on the development of eggs and larvae. - The study of the ontogenesis of the digestive functions and the nutritional needs of sea fish larvae, with bass as the model. The goal was to determine the specific nutritional needs of the young stages by studying the implementation and regulation of pancreatic and intestinal digestive enzymes. - The study of the regulation of certain developmental genes by means of nutrients, so as to understand how these nutrients behave during ontogenesis, particularly during development of the skeleton.
Ce mémoire est présentée par Chantal Cahu pour pour l'obtention d'une habilitation a diriger des recherches. Depuis 1981, son activité de recherche concerne l'étude de la nutrition des reproducteurs et des jeunes stades de développement d'organismes marins appartenant à deux embranchements différents, les crustacés et les poissons. Ce travail réalisé dans un organisme de recherche finalisée, l'Ifremer, se situe dans un programme plus général de développement de l'aquaculture. En effet, quelles que soient les espèces en jeu, le développement de l'aquaculture en France comme au niveau mondial repose sur la production de juvéniles en écloserie. Mon travail a donc plus précisément pour objectif l'acquisition de connaissances sur les besoins nutritionnels, les mécanismes de digestion et le développement des ces animaux afin d'améliorer la production de post-larves de crevettes et d'alevins de poissons en écloserie. Ce travail s'est déroulé en trois grandes périodes qui apparaissent dans ce mémoire : - L'étude de la nutrition des reproducteurs et son influence sur la qualité des oeufs et des larves de crevettes Pénéides. Mon travail a essentiellement porté sur l'effet des lipides et des vitamines sur le développement des oeufs et des larves. - L'étude de l'ontogenèse des fonctions digestives et les besoins nutritionnels des larves de poissons marins, avec le bar comme modèle. Le but était de déterminer les besoins nutritionnels spécifiques des jeunes stades, en étudiant la mise en place et la régulation des enzymes digestives pancréatiques et intestinales. - L'étude de la régulation de certains gènes du développement par les nutriments, de façon à comprendre comment ces nutriments agissent lors de l'ontogenèse, notamment lors du développement du squelette.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/rapport-2086.pdf
http://archimer.ifremer.fr/doc/00000/2086/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The replenishment and persistence of marine species is contingent on dispersing larvae locating suitable habitatand surviving to a reproductive stage. Pelagic larvae rely on environmental cues to make behavioural decisionswith chemical information being important for habitat selection at settlement. We explored the sensory worldof crustaceans and fishes focusing on the impact anthropogenic alterations (ocean acidification, red soil, pesti-cide) have on conspecific chemical signals used by larvae for habitat selection. Crustacean (Stenopus hispidus)and fish (Chromis viridis) larvae recognized their conspecifics via chemical signals under control conditions. Inthe presence of acidified water, red soil or pesticide, the ability of larvae to chemically recognize conspecificcues was altered. Our study highlights that recruitment potential on coral reefs may decrease due to anthropo-genic stressors. If so, populations of fishes and crustaceans will continue their rapid decline; larval recruitmentwill not replace and sustain the adult populations on degraded reefs
ISSN: 0025-326X

hal-01491052
https://hal-univ-perp.archives-ouvertes.fr/hal-01491052
DOI : 10.1016/j.marpolbul.2016.08.083

Éditeur(s) : HAL CCSD Linnean Society of London
Résumé : International audience
Although migratory pelagic fishes generally exhibit little geographic differentiation across oceans, as expected from their life-history (broadcast spawning, pelagic larval life, swimming ability of adults) and the assumed homogeneity of the pelagic habitat, exceptions to the rule deserve scrutiny. One such exception is the narrow-barred Spanish mackerel (Scomberomorus commerson), where strong genetic heterogeneity at the regional scale has been previously reported. We investigated the genetic composition of S. commerson across the Indo-West Pacific range using control-region sequences (including previously published datasets), cytochrome-b gene partial sequences, and eight microsatellite loci, to further explore its phylogeographic structure. All haplotypes sampled from the Indo-Malay-Papua archipelago (IMPA) and the southwestern Pacific coalesced into a clade (Clade II) that was deeply separated (14.5% nucleotide divergence) from a clade grouping all haplotypes from the Persian Gulf and Oman Sea (Clade I). Such a high level of genetic divergence suggested the occurrence of two sister-species. Further phylogeographic partition was evident between the western IMPA and the regions sampled east and south of it, i.e. northern Australia, West Papua, and the Coral Sea. Strong allele-frequency differences were found between local populations in the southwestern Pacific, both at the mitochondrial locus (ΦST=0.282-0.609) and at microsatellite loci (^θ=0.202-0.313). Clade II consisted of four deeply divergent subclades (9.0-11.8% nucleotide divergence for the control region; 0.3-2.5% divergence at the cytochrome b locus). Mitochondrial sub-clades within Clade II generally had narrow geographic distribution, demonstrating further genetic isolation. However, one particular haplogroup within Clade II was present throughout the central Indo-West Pacific; that haplogroup was found to be sister-group to an haplogroup restricted to West Papua and the Coral Sea, yielding evidence of recent secondary westward colonization. Such a complex structure is in sharp contrast with the generally weak phylogeographic patterns uncovered to date in other widely distributed, large pelagic fishes with pelagic eggs and larvae. We hypothesize that in S. commerson and possibly other Scomberomorus species, philopatric migration may play a role in maintaining the geographic isolation of populations by annihilating the potential consequences of passive dispersal.
ISSN: 0024-4066

ird-00759711
http://hal.ird.fr/ird-00759711
http://hal.ird.fr/ird-00759711v2/document
http://hal.ird.fr/ird-00759711/file/FauvelotBorsa_Scomberomorus%20commerson%20p%20HAL.pdf

Éditeur(s) : HAL CCSD Laboratoire Arago
Résumé : International audience
The analysis of the C-O stable isotope composition of coral reef fish otoliths from Taiaro, a French Polynesian atoll normally isolated from the Pacific Ocean, has been performed to address two main questions. The first is to confirm previous results which suggest that a lagoonal coral reef fish population is able to achieve its ontogenetic cycle without any open ocean phase. If so, are O isotopic values of otoliths an indicator of temperature fluctuations in the tropical Pacific Ocean related to climate change and in particular temperature variations of water masses? δ18O and δ13C values on both lagoon and open ocean fish otoliths caught in 2006 indicated clearly that O-isotopes reached the isotopic equilibrium; in contrast, all δ13C values exhibited a strong isotopic disequilibrium related to metabolic activity. Stable isotope compositions revealed a clear differentiation between fish from lagoons and those from the open ocean (with a δ18O enrichment of 1 ‰ in favour of the lagoon). This confirmed a lack of connectivity between habitats and that fish from lagoon lived their entire life cycle in the lagoon. Both δ18O and δ13C data indicated differences between nucleus and edge signatures with changes in fish behavior from the larval life to adulthood (habitat, diet, etc.), and a clear adaptation of dietary behavior of lagoon fish. The comparison of the 2006 data set with those of 1994 showed that environmental conditions were stable in the lagoon, leading to a very narrow range of variations in the δ18O values. δ18O of fish otoliths of the open ocean exhibited a wider variation (+0.25 ‰) between 1994 and 2006, suggesting a decrease in temperature linked to a change of SST, which can be interpreted in terms of climate change associated with El Nino Southern Oscilation (ENENSO). These differences could also be due to a switch of habitats during the life cycle of fish from the open ocean.
ISSN: 0240-8759

hal-01162477
https://hal-univ-perp.archives-ouvertes.fr/hal-01162477

Éditeur(s) : HAL CCSD eLife Sciences Publication
Résumé : International audience
Larval recruitment, the transition of pelagic larvae into reef-associated juveniles, is a critical step for the resilience of marine fish populations but its molecular control is unknown. Here, we investigate whether thyroid-hormones (TH) and their receptors (TR) coordinate the larval recruitment of the coral-reef-fish Acanthurus triostegus. We demonstrate an increase of TH-levels and TR-expressions in pelagic-larvae, followed by a decrease in recruiting juveniles. We generalize these observations in four other coral reef-fish species. Treatments with TH or TR-antagonist, as well as relocation to the open-ocean, disturb A. triostegus larvae transformation and grazing activity. Likewise, chlorpyrifos, a pesticide often encountered in coral-reefs, impairs A. triostegus TH-levels, transformation, and grazing activity, hence diminishing this herbivore’s ability to control the spread of reef-algae. Larval recruitment therefore corresponds to a TH-controlled metamorphosis, sensitive to endocrine disruption. This provides a framework to understand how larval recruitment, critical to reef-ecosystems maintenance, is altered by anthropogenic stressors.
ISSN: 2050-084X

Droits : http://creativecommons.org/licenses/by/
hal-01633712
http://hal.upmc.fr/hal-01633712
http://hal.upmc.fr/hal-01633712/document
http://hal.upmc.fr/hal-01633712/file/elife-27595-v1.pdf
DOI : 10.7554/eLife.27595