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Costa, C., Vandeputte, M., Antonucci, F., Boglione, C., De Verdal, H., & Chatain, B. (2015). Are trunk lateral line anomalies and disoriented scale patterns in European seabass (Dicentrarchus labrax) influenced by genetics? Aquaculture, 448, 38–43.
Résumé: Different kinds of defects are observed on farmed fish, and while a lot of research has concentrated on skeletal abnormalities, little is known on scale anomalies. We carried out a survey for lateral line shape anomalies and disorientated scale patterns on a batch composed of crosses of 5 different wild populations of European seabass, in order to find out whether there is a genetic basis to these anomalies. Lateral line shape was standardized coupling geometric morphometrics with advanced warping procedures based on thin-plate splines. Genetic variation between and within populations was found for lateral line shape, which was also affected by vertebral anomalies to a certain extent. Conversely, no significant genetic variation was found for scale disorientation, either between or within populations. We conclude that the shape of lateral line is probably not a decisive factor to externally evaluate spine anomalies; further, its variation is more likely linked to a general variation of fish shape than to impaired early development, while the cause of scale disorientations is more environmental than genetic.
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Fiandrino, A., Ouisse, V., Dumas, F., Lagarde, F., Pete, R., Malet, N., et al. (2017). Spatial patterns in coastal lagoons related to the hydrodynamics of seawater intrusion. Mar. Pollut. Bull., 119(1), 132–144.
Résumé: Marine intrusion was simulated in a choked and in a restricted coastal lagoon by using a 3D-hydrodynamic model. To study the spatiotemporal progression of seawater intrusion and its mixing efficiency with lagoon waters we define Marine Mixed Volume (V-MM) as a new hydrodynamic indicator. Spatial patterns in both lagoons were described by studying the time series and maps of VMM taking into account the meteorological conditions encountered during a water year. The patterns comprised well-mixed zones (WMZ) and physical barrier zones (PBZ) that act as hydrodynamic boundaries. The choked Bages-Sigean lagoon comprises four sub-basins: a PBZ at the inlet, and two WMZ's separated by another PBZ corresponding to a constriction zone. The volumes of the PBZ were 2.1 and 5.4 millions m(3) with characteristic mixing timescale of 68 and 84 days, respectively. The WMZ were 123 and 433 millions m(3) with characteristics mixing timescale of 70 and 39 days, respectively. (C) 2017 Elsevier Ltd. All rights reserved.
Mots-Clés: bay; confinement; estuary; Hydromorphological zonations; Mediterranean coastal lagoons; Mixing efficiency; model performance; Numerical model; sparus-aurata; Transport timescale; transport time scales; ulva rigida; venice lagoon; Water renewal; water renewal timescales; wind-driven circulation
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Goikoetxea, A., Sadoul, B., Blondeau-Bidet, E., Aerts, J., Blanc, M. - O., Parrinello, H., et al. (2021). Genetic pathways underpinning hormonal stress responses in fish exposed to short- and long-term warm ocean temperatures. Ecological Indicators, 120, 106937.
Résumé: Changes in ocean water temperature associated with global climate change are bound to enormously affect fish populations, with potential major economic consequences in the aquaculture and fisheries industries. A link between temperature fluctuations and changes in fish stress response is well established. In this study, we aimed to assess the effects of a short- (4 days) or a long-term (4 months) exposure to warm temperature in the stress physiology of European sea bass (Dicentrarchus labrax) larvae and juveniles. First, cortisol (i.e. the main stress hormone in fishes) analysis was used to confirm that a steady and short-term elevation of temperature acts as a physiological stressful event in these fish, and cortisol release is indeed above a metabolic increase linked to temperature. Moreover, our results verified that measurement of cortisol released into the water can be reliably employed as a non-invasive indicator of acute thermal stress in experimental conditions. Secondly, the different effects on the genetic cascade underlying the stress response between long-term low or high thermal treatments were evaluated at two larval development stages via candidate-gene and whole-transcriptome approaches. Interestingly, opposite expression for some key stress genes (nr3c1, nr3c2 and hsd11b2) were observed between developmental stages, highlighting the distinct adaptive mechanisms controlling the primary and secondary responses to a stressor. Surprising expression patterns for some understudied genes involved in the stress axis were also revealed, including crhr1, mc2r, mc5r, trh or trhr, which should be further explored. Finally, evaluation of cortisol content in scales was successfully used as a biomarker of chronic thermal stress, with 10x more cortisol in fish kept at 21 °C vs 16 °C after 4 months, supporting the gene expression results observed. The use of such a method as a proxy of long-term stress, unprecedented in the literature, holds a vast array of applications in further research, in particular, in the investigation of the impact of global warming on wild fish populations.
Mots-Clés: Commercial fish; Cortisol; Glucocorticoid receptors; Scales; Transcriptomics
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Leitao, R. P., Zuanon, J., Mouillot, D., Leal, C. G., Hughes, R. M., Kaufmann, P. R., et al. (2018). Disentangling the pathways of land use impacts on the functional structure of fish assemblages in Amazon streams. Ecography, 41(1), 219–232.
Résumé: Agricultural land use is a primary driver of environmental impacts on streams. However, the causal processes that shape these impacts operate through multiple pathways and at several spatial scales. This complexity undermines the development of more effective management approaches, and illustrates the need for more in-depth studies to assess the mechanisms that determine changes in stream biodiversity. Here we present results of the most comprehensive multi-scale assessment of the biological condition of streams in the Amazon to date, examining functional responses of fish assemblages to land use. We sampled fish assemblages from two large human-modified regions, and characterized stream conditions by physical habitat attributes and key landscape-change variables, including density of road crossings (i.e. riverscape fragmentation), deforestation, and agricultural intensification. Fish species were functionally characterized using ecomorphological traits describing feeding, locomotion, and habitat preferences, and these traits were used to derive indices that quantitatively describe the functional structure of the assemblages. Using structural equation modeling, we disentangled multiple drivers operating at different spatial scales, identifying causal pathways that significantly affect stream condition and the structure of the fish assemblages. Deforestation at catchment and riparian network scales altered the channel morphology and the stream bottom structure, changing the functional identity of assemblages. Local deforestation reduced the functional evenness of assemblages (i.e. increased dominance of specific trait combinations) mediated by expansion of aquatic vegetation cover. Riverscape fragmentation reduced functional richness, evenness and divergence, suggesting a trend toward functional homogenization and a reduced range of ecological niches within assemblages following the loss of regional connectivity. These results underscore the often-unrecognized importance of different land use changes, each of which can have marked effects on stream biodiversity. We draw on the relationships observed herein to suggest priorities for the improved management of stream systems in the multiple-use landscapes that predominate in human-modified tropical forests.
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