French Research Institute for Exploitation of the Sea
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Aquaculture potential evolution during early domestication trials in a model species (Danio rerio) with different breeding strategies
No full textDomestication is a cornerstone for diversifying aquaculture, and the feasibility of domesticating a wild fish population can be assessed through its aquaculture potential (i.e., a measure based on key phenotypic traits related to growth and reproduction in captivity while meeting stakeholders' expectations). As domestication modifies these traits, aquaculture potential is expected to evolve over generations, influenced by breeding strategies. However, little is known about how different management approaches may shape this evolution during early domestication. In this study, we tracked changes in aquaculture potential over four captive generations of wild-caught zebrafish (Danio rerio), subjected to three breeding strategies: no selection (NS), single-function selective breeding program (S-SBP; growth-related traits), and multi-function selective breeding program (M-SBP: growth, reproduction, welfare). S-SBP and M-SBP employed within-family selection based on a phenotypic index. We developed a standardized Aquaculture Potential Score (APS) integrating growth (standard length, height/length ratio, specific growth rate), reproductive (fecundity, sperm motility), and welfare traits (stress-induced cortisol, Fulton condition factor). Trait evolution was assessed using linear model predictions and genetic trends based on estimated breeding values and heritability derived from pedigrees. Selective breeding (S-SBP and M-SBP) rapidly improved growth and morphometric traits, whereas NS lines showed minimal change. Reproductive and welfare traits, however, remained largely static due to both low heritability (h2 < 0.20) and environmental modulation. Consequently, APS remained stable across generations, with growth gains offset by stagnation in other domains. These findings underscore that (i) early selection may effectively improve high-heritability traits; (ii) composite metrics like APS may obscure divergent trait responses
Platinum and Rare Earth Elements distribution in costal sediments from French western Mediterranean Sea
No full textThis study presents the first assessment of Technological Critical Elements (TCE), specifically platinum (Pt) and rare earth elements (REE), in coastal sediments along the French western Mediterranean Sea. These trace elements, increasingly used in advanced technologies, raise particular concerns due to their potential environmental impact. Surface sediment samples were collected from 21 stations along the French Mediterranean coast (from Spain border to Italy including Corsica Island) to evaluate TCE concentrations and identify potential sources. Most of the REE concentrations fell within expected natural levels and were mainly influenced by the geological characteristics of local watersheds, indicating a dominant geogenic origin. When normalized to European Shale, REE distribution patterns exhibited convex shapes, typical of coastal environments. In contrast, localized Pt enrichment were detected at specific sites, particularly in port areas, which could be linked to anthropogenic emissions from vehicular catalytic converters. These results highlight platinum as a relevant emerging contaminant in urban coastal environments. However, unexpected REE and Pt concentrations at the mouth of the Hérault river call for further investigation. This study highlights the importance of integrating geological background and anthropogenic pressures in coastal sediment quality assessments and supports the inclusion of TCE in long -term environmental monitoring programs in the Mediterranean Sea
Global ocean indicators: Marking pathways at the science-policy nexus
No full textOcean knowledge is crucial for shaping policies that enable sustainable development, adaptation, and well-being at all levels, as everyone—either directly or indirectly—depends on the ocean, which today faces escalating threats from climate change, pollution, and biodiversity loss, pushing us beyond critical planetary boundaries. Ocean indicators are crucial for translating ocean science and data into practical metrics, guidance, and tools informing on the state and health of the ocean that can be directly applied by policymakers, practitioners, and the public. Despite their critical importance, ocean indicators trail behind those for continental areas, limiting effective monitoring and policy integration. Developing reliable, comparable, and regularly updated ocean indicators, backed by a unified international framework, is essential for delivering coherent, actionable insights that can guide global goals and protect the ocean's future. This paper establishes a scientific foundation for ocean indicators through international and multidisciplinary collaboration, presenting defined criteria and a set of pilot indicators for the ocean’s physical, biogeochemical, biodiversity, and ecosystem aspects. The proposed framework offers a solid foundation for generating indicators that not only track the ocean state but also provide outputs for application in informing policy and decision-making
Shrimp hydrolysate-based palatability enhancer: A strategy to reduce fish-in fish-out ratio in marine fish species
No full textReducing the reliance of the aquaculture industry on wild fish resources remains a key challenge. Generally obtained from food coproducts, protein hydrolysates have emerged as promising functional and sustainable protein sources that can help compensate for the limitations of alternatives to marine proteins. In this study, we evaluated their use as a palatability enhancer (PE) by top-coating them directly on the feed, as a liquid and at low dose. We tested a PE made primarily from a shrimp liquid hydrolysate, as a cost-effective dietary solution to replace significant amounts of fish meal (FM) with plant proteins in juvenile red sea bream diets. The experimental feeds consisted in a high FM diet (HFM, 30% FM), a low FM diet (LFM, 15% FM) and two additional diets with 2% PE top-coated (HFM+PE and LFM+PE). Six replicate tanks, each containing fish weighing 27.2 ± 0.2 g, were provided with one of the test diets twice daily until apparent satiety for a duration of 15 weeks. Half of the tanks were exposed to an intermittent stress consisting in a 1 min net-chasing, 1 hour before their first meal. After the nutritional trial, individuals were subjected to an Edwarselia tarda challenge through injections. The basal diets, LFM and HFM, achieved comparable growth and feed efficiency. The use of LFM, therefore, mechanically reduced wild fish use by 25% if referring to the eFIFO index (Kok et al., 2020). PE supplementation in both diets resulted in enhanced fish growth and health performance, and improved feed use. Consequently, we estimated that PE use can significantly, and additionally, reduce by 6% the use of wild fish biomass in these conditions. The beneficial effects of PE on the growth performance were stable despite the stress challenge, which led however to overall strong reduction in growth performances in all groups. Survival was significantly increased by PE addition in response to the bacterial challenge compared to the LFM diet. All these results were supported by underlying physiological results. We concluded that liquid hydrolysate PE represent a great potential for feed formulators to cost-effectively reduce pressure on wild resources, while maintaining high performance of their feed
Welfare Indicators for Aquaculture Research: Toolboxes for Five Farmed European Fish Species
No full textRefining approaches to measuring, monitoring and appraising animal welfare in aquaculture research is key to (i) protecting and optimizing it, (ii) documenting the severity of how and when it deviates, and (iii) ensuring good scientific quality, reliable results and reproducibility, amongst other factors. However, different fish species and life stages can have varying welfare needs and assessing their welfare can be challenging. An array of welfare indicators (WIs) can be utilized when documenting fish welfare, and there is currently little consensus on which WIs are most applicable to the key fish species used in European aquaculture research. The aim of this review is to propose updated, fit for purpose and comprehensive WI toolboxes for aquaculture research involving Atlantic salmon ( Salmo salar ), rainbow trout ( Oncorhynchus mykiss ), European seabass ( Dicentrarchus labrax ), gilthead seabream ( Sparus aurata ), and the common carp ( Cyprinus carpio ). Where possible, these toolboxes will also include life‐stage considerations. It also provides information on utilizing WIs in deciding humane end‐points as well as information on how to sample different types of indicators. The review closes with information on how digitalization can affect the collection, collation and analysis of WI data in aquaculture research, including both practical and theoretical considerations. The toolboxes incorporate a range of WIs that go beyond those required for legally safeguarding fish welfare in both laboratory and operational experimental facilities in the current European 2010/63/EU Directive on the protection of animals used for scientific purposes and its amendment, the Commission Delegated Directive (EU) 2024/1262
Climatic and nutrient drivers affect long-term phytoplankton temporal trends in coastal lagoons
No full textUnderstanding how climate influences phytoplankton dynamics is crucial for anticipating temporal trends and cascading consequences on ecosystem functioning under climate change. This study explores long-term dynamics in contrasted Mediterranean lagoons and investigates the effects of climatic (air temperature, rainfall, wind speed) and nutrient (inorganic nutrient concentrations) drivers on phytoplankton chlorophyll a, abundances, and pigment composition. 17 years of summer monitoring were analyzed using univariate trend tests and multivariate approaches to highlight changes and to disentangle the contributions of abiotic factors to phytoplankton variability. Our results revealed contrasts among lagoons in physicochemical conditions and phytoplankton community, which strongly structured their temporal trends. Climatic drivers significantly influenced phytoplankton, but their importance was context-dependent. In nutrient-enriched systems, phytoplankton dynamics were primarily controlled by inorganic nutrient concentrations, while climatic effects were weak by comparison. Conversely, in nutrient-poor systems, climatic signals became more visible and influential: wind events were associated with higher chlorophyll a, warmer conditions with increases in phycoerythrin-rich picocyanobacteria, and rainfall with higher picoeukaryote abundances, potentially through indirect effects on water column stability and nutrient and light availability. However, under nutrient limitation, abundances remained low and dominated by small cells, suggesting that nutrient control exerts the strongest influence on phytoplankton, which may explain why nutrient control tends to mask diffuse climatic signals. Yet, climate change modulates physicochemical patterns and may progressively shape lagoon functioning. This study emphasizes the need to account for lagoon features and vulnerabilities, and supports adaptive and site-specific management strategies to safeguard coastal lagoons under future changes
Assessing the Effects of Three Harmful Microalgal Species on Spermatozoa and Embryos of the King Scallop Pecten Maximus
No full textThe reproductive process plays a crucial role in the renewal of populations of marine bivalves and represents an economic issue for exploited species like the king scallop Pecten maximus. However, environmental phenomena, such as harmful microalgal blooms (HAB), can affect key reproductive life stages, such as gametes and embryos. This study examines the effects of exposure to three harmful microalgal species (Alexandrium minutum, Lingulodinium polyedra, and Pseudo-nitzschia australis) on spermatozoa and embryos of king scallops P. maximus. The physiological responses of spermatozoa were evaluated after exposure to low (LC) and high concentrations (HC) of each microalgal species. While none of the tested microalgal strains showed direct toxicity, oxidative stress was associated to HC of A. minutum, and morphological changes were observed after exposure to L. polyedra and P. australis. Embryos of P. maximus were also exposed to HC of the same three microalgae species and examined under a microscope after 4h, 24h, and 48h of exposure. Exposure to A. minutum hindered cell division of embryos within the first four hours of development, leading to complete embryo lethality at 24 hours. No significant changes in early development were noted during the initial 48 hours of exposure to L. polyedra and P. australis. These findings underscore the diverse effects of harmful microalgal species, emphasizing the need for targeted fishery and shellfishery management, both spatially and temporally, especially when bivalves and harmful algal bloom species potentially coincide during bivalve reproduction and recruitment
Differences in telomere length and telomerase gene expression with age and among tissues in the Pacific oyster
No full textMarine organisms are continuously exposed to chemical stressors, highlighting the need for operational biomarkers that can be reliably implemented in biomonitoring programmes. Telomere length (TL) has emerged as a promising biomarker of cumulative stress, but its application in ecotoxicology remains limited due to two main challenges: (i) methodological difficulties in obtaining reliable TL measurements from preserved samples, and (ii) incomplete understanding of telomere dynamics across tissues and life stages in sentinel marine species.
In this study, we addressed both limitations in the Pacific oyster Crassostrea gigas. First, we compared different DNA extraction methods and selected a protocol suitable for isolating high-molecular-weight DNA from frozen oyster tissues. The qPCR assay was then optimized to minimise technical biases and ensure accurate TL quantification. Using this optimized method, we assessed TL variation across tissues and age classes. Significant tissue-specific differences were observed, with the digestive gland exhibiting the shortest telomeres. In addition, a clear age-related decrease in TL was detected across all tissues. Finally, RT-qPCR analyses revealed lower expression of the telomerase gene in adult tissues compared to early developmental stages, in line with the absence of detectable telomerase activity in adults.
Together, these findings provide a methodological and biological framework for future investigations into the effects of chemical stress on telomere dynamics in oysters
Using Mixed-clay Sediment Gravity Flow Rheology as an Indicator for Flow Velocity and Runout Distance
No full textIt is important to determine whether the dynamics of mixed-clay sediment gravity flows (SGFs) can be predicted from their dominant clay type, because natural SGF deposits can contain mixtures of clay minerals of different cohesive strength, and latitudinal zonation in clay mineral production may influence depositional patterns in mud-rich submarine fans. The present lock-exchange experiments produced high-density SGFs carrying different proportions of strongly cohesive bentonite clay and weakly cohesive kaolinite clay with a fixed 20% volumetric concentration. Head velocity and runout distance of the flows decreased, and starting suspension yield stress increased, as the bentonite fraction increased beyond 20%. However, for bentonite fractions ≤20%, the initial suspensions had lower yield stresses and the flows were more mobile than the pure kaolinite flow, implying that small bentonite fractions reduce the cohesive strength of the suspensions. Predictive equations for the yield stress, head velocity, and runout distance of mixed-clay flows, based on yield stresses of pure-clay constituents, indicate minimal interaction between the constituents for bentonite fractions ≤20%. However, for bentonite fractions >20%, the equations demonstrate an increasingly nonlinear interaction. These results suggest natural SGF dynamics and deposits may be sensitive to the most cohesive clay rather than the dominant clay
Le congrès One Ocean Science, un éclairage scientifique pour la 3e conférence des Nations unies sur l'Océan
No full textA defining feature of the 3rd United Nations Ocean Conference was its precursor: an international scientific congress designed to base political commitments on the best available knowledge. The analysis carried out in this article of the link between scientific recommendations and the commitments made highlights the value of such an approach, with the launch of several actions aimed at improving the protection and preservation of the ocean. This is the case, for example, with the establishment of a coalition of countries seeking to place the ocean at the heart of national climate plans, echoing the recommendation to use oceanbased approaches to achieve the objectives of the Paris Agreement. It is also the case with the significant increase in the surface area of marine protected areas, in response to the recommendation to protect marine ecosystems while honoring international commitments. The analysis also points to shortcomings, such as the failure of negotiations on the international plastics treaty. It further shows that certain issues raised by scientists, such as ocean-based food, have not been discussed during the conference. Overall, the efficacy of this science-policy interface argues strongly for its continuation at the 4th edition in 2028.La 3e conférence des Nations-Unies sur l’océan s’est distinguée des précédentes éditions par l’organisation en amont d’un congrès scientifique international. Celui-ci avait pour objectif de fournir des recommandations afin que les engagements pris par les Etats et gouvernements soient basés sur les meilleures connaissances scientifiques disponibles. Cet article analyse le lien entre les recommandations scientifiques et les engagements pris et montre l’intérêt d’une telle démarche avec le lancement de plusieurs actions visant à améliorer la protection et la préservation de l’océan. Elle pointe également des lacunes : certains sujets portés par les scientifiques n’ont pas trouvé écho dans l’agenda international dédié à l’océan. Le succès de la charnière colloque scientifique – conférence onusienne plaide pour sa reconduction lors de la 4e édition prévue en 202