INDITOL · Individual variation in tolerance of hypoxia and high temperatures in teleost fish: mechanisms and implications

Individual variation in tolerance of hypoxia and high temperatures in teleost fish: mechanisms and implications

• What is the problem/issue being addressed? Our oceans are changing. They are losing in their oxygen inventory and becoming more hypoxic. Hypoxia is a condition where the dissolved oxygen levels present in the water is becoming depleted. More than 700 coastal sites have been reported as new hypoxic or worsening in their oxygen conditions. With this recurrent environmental stressor, oceans are also becoming warmer. Hypoxia and acute warming share a common physiological mode of action in fishes, both stressors challenge the animal's capacity to provide sufficient O2 to respiring tissues. This can have severe consequences at the individual level, causing reduced performance and fitness, even threatening survival. Therefore, it is important to study the inter-individual variation in tolerance of these stressors within fish populations. This variation in tolerance will determine the ability of the population to persist, and even thrive, when challenged by these stressors. Why is it important for society? Investigations into physiological mechanisms that underlie tolerance of climate change are well-aligned with strategic priorities of the European Union and consist of one of the major societal challenges within the Horizon 2020 objectives. Determining the adaptive responses of fish populations towards two major environmental stressors will help us to predict the future of fisheries stocks and also improve sustainability of aquaculture by identifying robust strains. As fisheries and aquaculture, are both extremely important economic activities based on natural resources; with 1.2 million tonnes produced from EU aquaculture in 2012 of which 69% coming from marine water environment. Sustainable management of fisheries and aquaculture have been identified as an EU research and development priority, in accordance with the Horizon 2020 objectives. Current EU policy is committed to ensure the European fishing and aquaculture industry are sustainable, do not threaten fish population size, productivity and secure food quality and security over the long-term. The EU commission also recognizes that the impacts of climate and environmental changes on the marine environment are not fully understood and strongly encourage long-term scientific research project relevant to aquaculture management. The current project is fundamental research but is nonetheless perfectly in harmony with these EU policies and research objectives. It will provide important insights about how climate change stressors may affect the nature of populations of valuable coastal fishes, in terms of productivity (growth rates) and population dynamics (aging and life span). The proposed work will also inform about how selection for robust individuals in aquaculture may have correlated effects in terms of production and welfare. • What are the overall objectives? 1) To document variation in sub-lethal tolerance of hypoxia and acute warming in a population of juveniles, and reveal cross-tolerance 2) To demonstrate that relative tolerance depends upon each individual’s intrinsic respiratory physiology 3) To investigate how tolerance relates to underlying mitochondrial respiration 4) To evaluate whether tolerance trades-off against important individual traits such as growth efficiency 5) To evaluate the genomic links between maintenance metabolism and hypoxia tolerance and to estimate the heritability for these two traits

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