7 research outputs found
Role of the environment in the spatial dynamics of marine fishes at the sea-lagoon interface in the French Mediterranean : spatial ecology and ecophysiology approaches applied to three coastal species
La trĂšs grande majoritĂ© des organismes vivants se dĂ©placent au cours de leur vie et ce Ă des Ă©chelles spatio-temporelles trĂšs contrastĂ©es, du butinage des abeilles aux migrations emblĂ©matiques des baleines Ă bosses entre les tropiques et les pĂŽles. Lâun des grands dĂ©fis des Ă©cologistes du mouvement reste encore aujourdâhui de mieux comprendre les relations entre physiologie et dĂ©placement, souvent gouvernĂ©es par les variations environnementales. Le cĆur est un organe vital dont les battements reflĂštent directement les variations physiologiques imposĂ©es par lâenvironnement.Ce travail de doctorat, par une approche couplĂ©e de tĂ©lĂ©mĂ©trie acoustique et dâĂ©cophysiologie expĂ©rimentale, cherche Ă mieux comprendre lâimpact de lâenvironnement (1) sur les dĂ©placements de trois espĂšces de poissons cĂŽtiers emblĂ©matiques du golfe du Lion, la daurade royale Sparus aurata, le loup Dicentrachus labrax et la saupe Sarpa salpa, au sein de leur site dâalimentation en milieu lagunaire ainsi que (2) sur leurs migrations vers la mer. Les rĂ©sultats montrent que les trois modĂšles biologiques sont fortement rĂ©sidents dans la lagune pendant la pĂ©riode dâalimentation et y sont fidĂšles inter-annuellement, confirmant ainsi lâimportance du milieu lagunaire strict au sein de leur cycle de vie. Le dĂ©veloppement dâune technique dâimplantation de capteurs mesurant la frĂ©quence cardiaque de daurades dâĂ©levage en nage libre sâest rĂ©vĂ©lĂ© efficace pour dĂ©terminer des seuils de tolĂ©rance pertinents au rĂ©chauffement. Cette technique a Ă©tĂ© appliquĂ©e pour la premiĂšre fois Ă des daurades sauvages afin de dĂ©terminer des seuils de tolĂ©rance Ă la baisse ou Ă la hausse de tempĂ©ratures et de les relier aux mouvements observĂ©s en milieu naturel. Les conclusions sont que (1) la tempĂ©rature semble avoir trĂšs peu dâinfluence sur lâutilisation de lâespace lagunaire des daurades en phase dâalimentation, mais (2) quâelle est le principal dĂ©clencheur de migrations de refuge vers la mer durant les Ă©pisodes de forte chaleur et vraisemblablement le principal facteur empĂȘchant les daurades dâhiverner au sein de la lagune. Enfin, (3) la photopĂ©riode, probablement en lien avec la tempĂ©rature, apparait comme le principal dĂ©clencheur des dĂ©parts en migrations de reproduction des daurades, ce que leur synchronisation de ces dĂ©parts semble confirmer. LâĂ©tude des rĂ©ponses cardiaques au rĂ©chauffement a montrĂ© que 29°C est un seuil de tolĂ©rance pertinent au rĂ©chauffement ce qui semble ĂȘtre en accord avec les tempĂ©ratures initiant les migrations de refuge. En revanche, aucun seuil nâa pu ĂȘtre clairement identifiĂ© Ă partir de la rĂ©ponse cardiaque au refroidissement.Plus gĂ©nĂ©ralement, cette Ă©tude dĂ©montre la pertinence dâune approche multidisciplinaire pour lâĂ©tude des mouvements.The vast majority of living organisms move during their lives and at very different scales, from the foraging of bees to the emblematic migrations of humpback whales between the poles and the tropics. One of the major challenges for movement ecologists is to better understand the physiology behind these movements, which are often triggered by the environment. The heart is a vital organ whose activity can directly reflect physiological constraints imposed by the environment.This doctoral research, using a coupled approach of acoustic telemetry and experimental ecophysiology, sought to better understand the impact of the environment on the movements of three emblematic species of coastal marine fishes in the Gulf of Lion, the gilthead seabream Sparus aurata, the European seabass Dicentrarchus labrax and the salema Sarpa salpa. I studied theirs movements within their seasonal foraging ground in a coastal lagoon (Ătang du PrĂ©vost) and their migrations from the lagoon to sea at different time scales. All three species were highly resident in the lagoon during the foraging season and all showed inter-annual fidelity to it, demonstrating the importance of lagoon environments in the life cycle of coastal fishes. Using cultured seabream, I developed a method to instrument them with archival (biologging) tags to measure their heart rate while free-swimming. I then demonstrated that measures of cardiac activity can evaluate impacts of environmental factors (warming, hypoxia) on seabream physiology, including tolerance thresholds. I then used this approach on wild seabream, to evaluate cardiac responses to temperature and determine their tolerance thresholds, as a basis to interpret movements in the wild. Temperature seemed to have little influence on patterns of lagoon space use by the seabream during the foraging season. Dominance analysis revealed, however, that temperature was the main trigger for refuge migrations to the sea during summer heat waves and was also the main factor defining when seabream could first recolonise the lagoon after winter at sea. Photoperiod, probably combined with temperature, appeared to be the main trigger for the departure of seabream from the lagoon in autumn, for their breeding migration, which seemed to be confirmed by their extreme synchronization. In general, temperatures that seabream experienced in the lagoon were well within their range of physiological tolerance. Cardiac responses to warming revealed, however, that 29°C was a relevant threshold of upper tolerance which seemed in close agreement with the summer heatwave temperatures that stimulated refuge migrations out to sea. However, no relevant threshold could be deduced from cardiac responses to cooling. Overall, the research demonstrated that a multidisciplinary approach holds much promise for understanding the drivers of movements of wild marine fishes
RÎle de l'environnement dans la dynamique spatiale des poissons marins à l'interface lagune-mer en Méditerranée française : approches d'écologie spatiale et d'écophysiologie appliquées à trois espÚces cÎtiÚres
The vast majority of living organisms move during their lives and at very different scales, from the foraging of bees to the emblematic migrations of humpback whales between the poles and the tropics. One of the major challenges for movement ecologists is to better understand the physiology behind these movements, which are often triggered by the environment. The heart is a vital organ whose activity can directly reflect physiological constraints imposed by the environment.This doctoral research, using a coupled approach of acoustic telemetry and experimental ecophysiology, sought to better understand the impact of the environment on the movements of three emblematic species of coastal marine fishes in the Gulf of Lion, the gilthead seabream Sparus aurata, the European seabass Dicentrarchus labrax and the salema Sarpa salpa. I studied theirs movements within their seasonal foraging ground in a coastal lagoon (Ătang du PrĂ©vost) and their migrations from the lagoon to sea at different time scales. All three species were highly resident in the lagoon during the foraging season and all showed inter-annual fidelity to it, demonstrating the importance of lagoon environments in the life cycle of coastal fishes. Using cultured seabream, I developed a method to instrument them with archival (biologging) tags to measure their heart rate while free-swimming. I then demonstrated that measures of cardiac activity can evaluate impacts of environmental factors (warming, hypoxia) on seabream physiology, including tolerance thresholds. I then used this approach on wild seabream, to evaluate cardiac responses to temperature and determine their tolerance thresholds, as a basis to interpret movements in the wild. Temperature seemed to have little influence on patterns of lagoon space use by the seabream during the foraging season. Dominance analysis revealed, however, that temperature was the main trigger for refuge migrations to the sea during summer heat waves and was also the main factor defining when seabream could first recolonise the lagoon after winter at sea. Photoperiod, probably combined with temperature, appeared to be the main trigger for the departure of seabream from the lagoon in autumn, for their breeding migration, which seemed to be confirmed by their extreme synchronization. In general, temperatures that seabream experienced in the lagoon were well within their range of physiological tolerance. Cardiac responses to warming revealed, however, that 29°C was a relevant threshold of upper tolerance which seemed in close agreement with the summer heatwave temperatures that stimulated refuge migrations out to sea. However, no relevant threshold could be deduced from cardiac responses to cooling. Overall, the research demonstrated that a multidisciplinary approach holds much promise for understanding the drivers of movements of wild marine fishes.La trĂšs grande majoritĂ© des organismes vivants se dĂ©placent au cours de leur vie et ce Ă des Ă©chelles spatio-temporelles trĂšs contrastĂ©es, du butinage des abeilles aux migrations emblĂ©matiques des baleines Ă bosses entre les tropiques et les pĂŽles. Lâun des grands dĂ©fis des Ă©cologistes du mouvement reste encore aujourdâhui de mieux comprendre les relations entre physiologie et dĂ©placement, souvent gouvernĂ©es par les variations environnementales. Le cĆur est un organe vital dont les battements reflĂštent directement les variations physiologiques imposĂ©es par lâenvironnement.Ce travail de doctorat, par une approche couplĂ©e de tĂ©lĂ©mĂ©trie acoustique et dâĂ©cophysiologie expĂ©rimentale, cherche Ă mieux comprendre lâimpact de lâenvironnement (1) sur les dĂ©placements de trois espĂšces de poissons cĂŽtiers emblĂ©matiques du golfe du Lion, la daurade royale Sparus aurata, le loup Dicentrachus labrax et la saupe Sarpa salpa, au sein de leur site dâalimentation en milieu lagunaire ainsi que (2) sur leurs migrations vers la mer. Les rĂ©sultats montrent que les trois modĂšles biologiques sont fortement rĂ©sidents dans la lagune pendant la pĂ©riode dâalimentation et y sont fidĂšles inter-annuellement, confirmant ainsi lâimportance du milieu lagunaire strict au sein de leur cycle de vie. Le dĂ©veloppement dâune technique dâimplantation de capteurs mesurant la frĂ©quence cardiaque de daurades dâĂ©levage en nage libre sâest rĂ©vĂ©lĂ© efficace pour dĂ©terminer des seuils de tolĂ©rance pertinents au rĂ©chauffement. Cette technique a Ă©tĂ© appliquĂ©e pour la premiĂšre fois Ă des daurades sauvages afin de dĂ©terminer des seuils de tolĂ©rance Ă la baisse ou Ă la hausse de tempĂ©ratures et de les relier aux mouvements observĂ©s en milieu naturel. Les conclusions sont que (1) la tempĂ©rature semble avoir trĂšs peu dâinfluence sur lâutilisation de lâespace lagunaire des daurades en phase dâalimentation, mais (2) quâelle est le principal dĂ©clencheur de migrations de refuge vers la mer durant les Ă©pisodes de forte chaleur et vraisemblablement le principal facteur empĂȘchant les daurades dâhiverner au sein de la lagune. Enfin, (3) la photopĂ©riode, probablement en lien avec la tempĂ©rature, apparait comme le principal dĂ©clencheur des dĂ©parts en migrations de reproduction des daurades, ce que leur synchronisation de ces dĂ©parts semble confirmer. LâĂ©tude des rĂ©ponses cardiaques au rĂ©chauffement a montrĂ© que 29°C est un seuil de tolĂ©rance pertinent au rĂ©chauffement ce qui semble ĂȘtre en accord avec les tempĂ©ratures initiant les migrations de refuge. En revanche, aucun seuil nâa pu ĂȘtre clairement identifiĂ© Ă partir de la rĂ©ponse cardiaque au refroidissement.Plus gĂ©nĂ©ralement, cette Ă©tude dĂ©montre la pertinence dâune approche multidisciplinaire pour lâĂ©tude des mouvements
RÎle de l'environnement dans la dynamique spatiale des poissons marins à l'interface lagune-mer en Méditerranée française : approches d'écologie spatiale et d'écophysiologie appliquées à trois espÚces cÎtiÚres
The vast majority of living organisms move during their lives and at very different scales, from the foraging of bees to the emblematic migrations of humpback whales between the poles and the tropics. One of the major challenges for movement ecologists is to better understand the physiology behind these movements, which are often triggered by the environment. The heart is a vital organ whose activity can directly reflect physiological constraints imposed by the environment.This doctoral research, using a coupled approach of acoustic telemetry and experimental ecophysiology, sought to better understand the impact of the environment on the movements of three emblematic species of coastal marine fishes in the Gulf of Lion, the gilthead seabream Sparus aurata, the European seabass Dicentrarchus labrax and the salema Sarpa salpa. I studied theirs movements within their seasonal foraging ground in a coastal lagoon (Ătang du PrĂ©vost) and their migrations from the lagoon to sea at different time scales. All three species were highly resident in the lagoon during the foraging season and all showed inter-annual fidelity to it, demonstrating the importance of lagoon environments in the life cycle of coastal fishes. Using cultured seabream, I developed a method to instrument them with archival (biologging) tags to measure their heart rate while free-swimming. I then demonstrated that measures of cardiac activity can evaluate impacts of environmental factors (warming, hypoxia) on seabream physiology, including tolerance thresholds. I then used this approach on wild seabream, to evaluate cardiac responses to temperature and determine their tolerance thresholds, as a basis to interpret movements in the wild. Temperature seemed to have little influence on patterns of lagoon space use by the seabream during the foraging season. Dominance analysis revealed, however, that temperature was the main trigger for refuge migrations to the sea during summer heat waves and was also the main factor defining when seabream could first recolonise the lagoon after winter at sea. Photoperiod, probably combined with temperature, appeared to be the main trigger for the departure of seabream from the lagoon in autumn, for their breeding migration, which seemed to be confirmed by their extreme synchronization. In general, temperatures that seabream experienced in the lagoon were well within their range of physiological tolerance. Cardiac responses to warming revealed, however, that 29°C was a relevant threshold of upper tolerance which seemed in close agreement with the summer heatwave temperatures that stimulated refuge migrations out to sea. However, no relevant threshold could be deduced from cardiac responses to cooling. Overall, the research demonstrated that a multidisciplinary approach holds much promise for understanding the drivers of movements of wild marine fishes.La trĂšs grande majoritĂ© des organismes vivants se dĂ©placent au cours de leur vie et ce Ă des Ă©chelles spatio-temporelles trĂšs contrastĂ©es, du butinage des abeilles aux migrations emblĂ©matiques des baleines Ă bosses entre les tropiques et les pĂŽles. Lâun des grands dĂ©fis des Ă©cologistes du mouvement reste encore aujourdâhui de mieux comprendre les relations entre physiologie et dĂ©placement, souvent gouvernĂ©es par les variations environnementales. Le cĆur est un organe vital dont les battements reflĂštent directement les variations physiologiques imposĂ©es par lâenvironnement.Ce travail de doctorat, par une approche couplĂ©e de tĂ©lĂ©mĂ©trie acoustique et dâĂ©cophysiologie expĂ©rimentale, cherche Ă mieux comprendre lâimpact de lâenvironnement (1) sur les dĂ©placements de trois espĂšces de poissons cĂŽtiers emblĂ©matiques du golfe du Lion, la daurade royale Sparus aurata, le loup Dicentrachus labrax et la saupe Sarpa salpa, au sein de leur site dâalimentation en milieu lagunaire ainsi que (2) sur leurs migrations vers la mer. Les rĂ©sultats montrent que les trois modĂšles biologiques sont fortement rĂ©sidents dans la lagune pendant la pĂ©riode dâalimentation et y sont fidĂšles inter-annuellement, confirmant ainsi lâimportance du milieu lagunaire strict au sein de leur cycle de vie. Le dĂ©veloppement dâune technique dâimplantation de capteurs mesurant la frĂ©quence cardiaque de daurades dâĂ©levage en nage libre sâest rĂ©vĂ©lĂ© efficace pour dĂ©terminer des seuils de tolĂ©rance pertinents au rĂ©chauffement. Cette technique a Ă©tĂ© appliquĂ©e pour la premiĂšre fois Ă des daurades sauvages afin de dĂ©terminer des seuils de tolĂ©rance Ă la baisse ou Ă la hausse de tempĂ©ratures et de les relier aux mouvements observĂ©s en milieu naturel. Les conclusions sont que (1) la tempĂ©rature semble avoir trĂšs peu dâinfluence sur lâutilisation de lâespace lagunaire des daurades en phase dâalimentation, mais (2) quâelle est le principal dĂ©clencheur de migrations de refuge vers la mer durant les Ă©pisodes de forte chaleur et vraisemblablement le principal facteur empĂȘchant les daurades dâhiverner au sein de la lagune. Enfin, (3) la photopĂ©riode, probablement en lien avec la tempĂ©rature, apparait comme le principal dĂ©clencheur des dĂ©parts en migrations de reproduction des daurades, ce que leur synchronisation de ces dĂ©parts semble confirmer. LâĂ©tude des rĂ©ponses cardiaques au rĂ©chauffement a montrĂ© que 29°C est un seuil de tolĂ©rance pertinent au rĂ©chauffement ce qui semble ĂȘtre en accord avec les tempĂ©ratures initiant les migrations de refuge. En revanche, aucun seuil nâa pu ĂȘtre clairement identifiĂ© Ă partir de la rĂ©ponse cardiaque au refroidissement.Plus gĂ©nĂ©ralement, cette Ă©tude dĂ©montre la pertinence dâune approche multidisciplinaire pour lâĂ©tude des mouvements
RÎle des lagunes littorales dans le cycle biologique des poissons méditerranéens: comprendre pour mieux préserver
Les lagunes mĂ©diterranĂ©ennes sont aujourdâhui dĂ©crites comme des habitats essentiels au cycle de vie de nombreuses espĂšces de poissons cĂŽtiers quâelles soient sĂ©dentaires ou migratrices. Ces masses dâeau, relativement confinĂ©es, prĂ©sentes en effet des caractĂ©ristiques environnementales permettant de maximiser la croissance des juvĂ©niles et dâoptimiser la survie des adultes (abondance en nourriture, tempĂ©rature plus Ă©levĂ©e, prĂ©dation limitĂ©eâŠ) mais celles-ci varient spatialement et temporellement au sein mĂȘme dâune lagune sous lâinfluence de facteurs naturels et anthropiques. Comprendre le lien entre les habitats et les poissons nĂ©cessite donc de qualifier et quantifier ces interactions Ă ces Ă©chelles de temps et dâespace afin dâĂȘtre en mesure dâadapter in fine la gestion de ces milieux pour renforcer leurs rĂŽles dans le cycle de vie des espĂšces de poissons lagunaires et cĂŽtiers. Au stade juvĂ©nile, lâattractivitĂ© des habitats lagunaires variraient selon lâespĂšce et le stade de vie, aussi bien pour les juvĂ©niles des espĂšces migratrices que pour ceux des espĂšces rĂ©sidentes. La prĂ©sence de macrophytes et en particulier de macroalgues sur le fond jouerait un rĂŽle essentiel en structurant dâune part les habitats pour les juvĂ©niles (zone de refuge, abrits de proies) et en contribuant dâautre part au rĂ©gime trophique de maniĂšre directe ou indirecte. Ces rĂ©sultats permettent de mieux dĂ©finir la notion de nurserie en considĂ©rant une mosaĂŻque dâhabitats qui assure des fonctions complĂ©mentaires pour les juvĂ©niles de poissons. Au stade adulte, la dynamique spatiale de trois espĂšces modĂšle (Dicentrarchus labrax, Salpa salpa et Sparus aurata) en relation avec les habitats que ces lagunes suivie par tĂ©lĂ©mĂ©trie acoustique illustre le rĂŽle clĂ©s de ces habitats lagunaire probablement en fournissant un habitat dâalimentation rĂ©pondant Ă leurs besoins en termes de croissance. Pour ces trois espĂšces, un effet saisonnier important dans sa frĂ©quentation, essentiellement durant la phase hivernale en lien avec les basses tempĂ©ratures et la phase de reproduction a ainsi pu ĂȘtre dĂ©montrĂ© avec une forte fidĂ©litĂ© dâune annĂ©e sur lâautre Ă la lagune. Sur la base de ces nouvelles connaissances, le maintien ou la restauration des fonctions assurĂ©es par une mosaĂŻque dâhabitats lagunaires semble ainsi ĂȘtre un des futurs enjeux majeurs au vu de la fragilitĂ© de ces Ă©cosystĂšmes aux pressions anthropiques an particulier aujourdâhui dans un contexte de changement climatique, de dĂ©gradation des habitats et dâabsence de mesures de gestions des pĂȘcheries durables
Residency, home range and inter-annual fidelity of three coastal fish species in a Mediterranean coastal lagoon
International audienceIn the Gulf of Lion (NW Mediterranean), fish species such as gilthead sea bream Sparus aurata, European seabass Dicentrarchus labrax, and salema Sarpa salpa show seasonal occupation of coastal lagoons, presumably as feeding grounds during their adult life stage. The role of the lagoons in these species; life cycles remains unknown, particularly with respect to their residency, space-use, and inter-annual fidelity. Using acoustic telemetry, the movements of 72 seabream, 58 seabass, and 81 salema were monitored over four years within PrĂ©vost Lagoon (HĂ©rault Department, Occitania Region), to characterise (1) the main seasonal patterns of space use inside the lagoon and (2) their annual migrations between the lagoon and the sea. Overall, all three species were highly resident in the lagoon during the spring/summer foraging season; seabass was the only species that also displayed high residency to the lagoon throughout the winter breeding season. The three species showed differences in their space use, although they all mainly inhabited the deep lagoon centre and adjacent shellfish farms, with very small individual home ranges (meanâŻÂ±âŻSD, 0.12âŻÂ±âŻ0.06 km2 over all species). All species showed some inter-annual fidelity to the lagoon (>43% at minimum for seabream) although these fidelity rates were probably underestimated due to fishing mortality, which is probably high during the winter breeding season. Overall, this study reveals that coastal lagoons are key foraging habitats for these species in the Gulf of Lion. The high residency and inter-annual fidelity suggest that any increase of anthropogenic pressure within the lagoon could negatively impact these fish populations. Therefore, protection of such productive habitats could be beneficial for long-term management of emblematic coastal species and the fisheries that they support
Cardiac and behavioural responses to hypoxia and warming in free-swimming gilthead seabream, Sparus aurata
WOS:000681398200011International audienceGilthead seabream were equipped with intraperitoneal biologging tags to investigate cardiac responses to hypoxia and warming, comparing when fish were either swimming freely in a tank with conspecifics or confined to individual respirometers. After tag implantation under anaesthesia, heart rate (f(H)) required 60 h to recover to a stable value in a holding tank. Subsequently, when undisturbed under control conditions (normoxia, 21 degrees C), mean f(H) was always significantly lower in the tank than in the respirometers. In progressive hypoxia (100% to 15% oxygen saturation), mean f(H) in the tank was significantly lower than in the respirometers at oxygen levels down to 40%, with significant bradycardia in both holding conditions below this level. Simultaneous logging of tri-axial body acceleration revealed that spontaneous activity, inferred as the variance of external acceleration (VAR(m)), was low and invariant in hypoxia. Warming (21 to 31 degrees C) caused progressive tachycardia with no differences in f(H) between holding conditions. Mean VAR(m) was, however, significantly higher in the tank during warming, with a positive relationship between VAR(m) and f(H) across all temperatures. Therefore, spontaneous activity contributed to raising f(H) of fish in the tank during warming. Mean f(H) in respirometers had a highly significant linear relationship with mean rates of oxygen uptake, considering data from hypoxia and warming together. The high f(H) of confined seabream indicates that respirometry techniques may bias estimates of metabolic traits in some fishes, and that biologging on free-swimming fish will provide more reliable insight into cardiac and behavioural responses to environmental stressors by fish in their natural environment
Farmed bivalve loss due to seabream predation in the French Mediterranean Prevost Lagoon
Bivalve predation by seabream has been observed worldwide and is a major concern for bivalve farmers. Farmed bivalve-seabream interactions must be better understood to ensure the sustainability of bivalve aquaculture. The objectives of this study were to characterize gilthead seabream Sparus aurata presence in a bivalve farm in Prevost Lagoon (Mediterranean Sea) using acoustic telemetry and to evaluate monthly losses of mussels Mytilus galloprovincialis and oysters Crassostrea gigas due to seabream predation over an 18 mo period inside the farm and at an unprotected experimental platform. Large (281 to 499 mm TL) seabream were more commonly detected in the bivalve farm than were small (200 to 280 mm TL) seabream. In contrast to small seabream, 90% of large seabream returned to and spent extended periods in the study area the following year, suggesting inter-annual site fidelity for large fish that used the bivalve farm as a feeding site. Signs of predation were observed on mussels and oysters throughout the year at the unprotected experimental platform. Farmers noted losses in the farm from April to September. Maximal losses (90 to 100%) were observed post-oyster âstickingâ and mussel socking. Despite the deployment of nets as mechanical protection to reduce predation, oyster losses represented 28% of the annual value of oysters sold while mussel losses were estimated at ca. 1%. These results suggest that bivalves must be protected by nets throughout the year to avoid predation, particularly post-handling. A collaboration between shellfish farmers and fishermen could be a sustainable solution for bivalve farming, by regularly fishing for seabream in farms, between tables and inside protective nets