French Research Institute for Exploitation of the Sea
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Population genetic diversity and structure of wild and hatchery-raised populations of European abalone Haliotis tuberculata tuberculata: guidelines for future restocking and stock-enhancement programs
No full textPopulations of Haliotis tuberculata tuberculata declined sharply over the last two decades, mainly due to pathogenic bacteria, Vibrio Harveyi. In this context, restocking or stock-enhancement operations based on hatchery juveniles might be relevant to restore populations and ensure sustainable fisheries. Maintaining the genetic diversity of wild populations and hatchery individuals is a primary concern in supplementation programs. Here, the genetic diversity of 14 hatchery samples and ten wild populations was assessed using 158 nuclear SNPs. Genetic diversity was comparable between wild and hatchery samples, and even slightly higher in the hatchery. However, high genetic differentiation and small effective population sizes suggested strong genetic drift in the hatchery. Pooling hatchery samples decreased differentiation levels with wild samples, suggesting that released juveniles should be composed of several cohorts and/or generations to limit the genetic heterogeneity between seed and wild populations. Moreover, reduced connectivity was detected between northwestern and southeastern populations, suggesting that restocking broodstock should be chosen depending on the locality where it would be released. Overall, this study provides useful guidelines for future restocking programs
Sea Ice as a Driver of Fin Whale (Balaenoptera physalus) 20 Hz Acoustic Presence in Eastern Antarctic Waters
No full textThe environmental drivers of fin whale (Balaenoptera physalus) acoustic presence in Eastern Antarctic waters were investigated based on passive acoustic recordings from four sites, 2013–2019. Fin whale 20 Hz pulses were detected from late austral summer to early winter. Daily values of sea-ice concentration (SIC) were compared with the number of days with fin whale 20 Hz acoustic presence using a generalized additive model approach. At the Southern Kerguelen Plateau, Casey, and Dumont d’Urville sites, SIC correlated with fin whale calling activity, but less so at the Prydz site. Changes in SIC between sites resulted in variation in acoustic presence: Earlier sea-ice formation at Dumont d’Urville resulted in less acoustic presence in comparison to the Southern Kerguelen Plateau, where sea ice formed later in the season. Interannual variability in SIC impacted yearly acoustic presence, with a later onset of high SIC resulting in greater acoustic presence and later departure (migration timing) of the animals. Identifying the environmental drivers of fin whale presence is key to informing how this migratory species may be affected by environmental variability resulting from climate change
Nutrient estimation in the Peruvian upwelling system based on a neural network approach
No full textThis study presents a regionally trained version of the “CArbonate system and Nutrients concentration from hYdrological properties and Oxygen using a Neural network” (CANYON) method, named CANYON-PU, for estimating primary macronutrients (phosphates, silicates, and nitrates) in the Peruvian Upwelling System (PUS). Using a neural network approach, the model was trained using extensive biogeochemical data spanning between 2003 and 2021, collected by the Peruvian Institute of Marine Research (IMARPE). Variables representing the low-frequency variability related to ENSO were introduced in the training and significantly improved the performance of the algorithm. The performance of CANYON-PU was validated against independent datasets and demonstrated an improvement in accuracy over the global CANYON model that struggled to represent the nutrient distribution in the PUS mainly due to the lack of samples in its training. Therefore, CANYON-PU successfully captured nutrient variability across different spatial and temporal scales, showcasing its applicability to diverse datasets, including high-frequency data such as profiling floats or gliders. This work highlights the effectiveness of neural networks for representing the nutrient distribution within highly variable ecosystems like the PUS
The Fast-Greedy algorithm reveals hourly fluctuations and associated risks of shark communities in a South Pacific city
No full textUnprovoked shark bites are increasing globally. Regional hotspots like Nouméa show rising incidents involving bull sharks (Carcharhinus leucas) and tiger sharks (Galeocerdo cuvier), leading to the culling of these protected species. Identifying high-risk areas and times is key to balancing human safety and shark conservation. Here, we collected five years of acoustic telemetry data for both shark species in the lagoon of Nouméa. The data were categorized by species, divided into 24 hourly subsets, and modeled as bipartite graphs. The Fast-Greedy algorithm was applied to identify distinct communities of sharks and stations. Normalized mutual information was used to cluster communities and detect spatiotemporal patterns. The study revealed up to 9 hourly communities for bull sharks and 21 for tiger sharks, each grouping into 3 clusters. Several high-risk areas and times were identified. Bull sharks formed schools, and a cluster was observed in the harbor between 6:00 and 13:00, increasing bite risk on nearby beaches in the morning. Tiger sharks were more solitary and were present day and night at most stations except those in relatively turbid areas. Both species showed fission–fusion dynamics, with communities merging at dusk, indicating increased movement and a higher risk during this low-light period. A key innovation of our modelling framework was its ability to handle temporal variability in community detection algorithms applied to bipartite networks. The model identified key overlap periods of shark-human activity, highlighting the need for real-time monitoring, safety measures, and public awareness to reduce bite risk and promote coexistence
Évaluation de la qualité des zones de production conchylicole. Région Occitanie – Période 2022-2024
No full textAprès un rappel des objectifs, du fonctionnement et de la méthode d’interprétation des résultats du réseau de surveillance microbiologique (REMI) et du réseau de surveillance chimique (ROCCH), ce rapport présente un bilan national et décrit le programme annuel 2024 de la région Occitanie. Il reprend l’ensemble des résultats obtenus, en particulier l’estimation de la qualité microbiologique et chimique des zones classées de production de coquillages. En 2024, 22 zones de production, dont 14 zones pêche et 8 d’élevage, ont été suivies en région Occitanie au travers de 28 lieux du réseau de surveillance microbiologique REMI et 11 lieux du volet sanitaire du réseau de surveillance de la contamination chimique ROCCH. Les programmes de surveillance ont été conduits avec un taux de réalisation des prélèvements et analyses de 100 % pour le ROCCH et de 95,3% pour le REMI. L’année 2024 a été marquée par le transfert du déclenchement et de la diffusion des bulletins d’alerte de l’Ifremer vers la DDPP34 en juillet. Au total, 33 épisodes de vigilance ou d’alerte ont été déclenchés et suivis en Occitanie et ont concerné 11 zones. Les 2 épisodes marquants de contamination microbiologique suivis en alerte de niveau 2 ont concerné la (même) zone de pêche de palourdes n°34.38.02 « Lagune de Thau - Mèze Conque » qui est, parmi l’ensemble des zones actuellement suivies en Occitanie, la plus fréquemment exposée à des pics de contamination. La qualité microbiologique estimée en 2025 à partir des résultats de la période 2022-24 est A pour 4 zones d’élevage localisées au large en mer sur les filières (18,2%), B pour 10 zones (45,5%), C pour 5 zones (22,7%) et très mauvaise pour 2 zones (9,1%). La qualité ne peut être estimée pour 1 zone. La qualité chimique est satisfaisante pour l’ensemble des points suivis. Toutefois, le suivi des dioxines, PCB et HAP règlementés n’a pas été programmé sur la période 2022-2024 pour 5 des 11 lieux suivis en raison d’une absence de financement. Leur qualité chimique vis-à-vis de ces substances repose ainsi sur celle de la période précédente. Parmi ces zones, 16 ont un classement sanitaire concordant avec l’estimation de leur qualité, 5 ont un classement sanitaire plus favorable que l’estimation de leur qualité.
Parmi ces zones, 16 ont un classement sanitaire concordant avec l’estimation de leur qualité, 5 ont un classement sanitaire plus favorable que l’estimation de leur qualité
Catalyzing change: a literature review on the implementation of the Nature Futures Framework
No full textThe Nature Futures Framework (NFF), developed under the Intergovernmental Science–Policy Platform on Biodiversity and Ecosystem Services (IPBES), serves as a catalyst for advancing new scenarios and models focused on biodiversity and ecosystem services within the broader research community. In particular, the framework facilitates the development of scenarios and models that can help guide change processes toward desirable futures for nature and people. This paper assesses 31 studies that have engaged with the NFF since its introduction in 2020, aiming to identify which research areas have been addressed, and where development needs remain. The applications exhibit a large diversity in terms of locations, spatial scales, methods, outputs, and stakeholder involvement. The most common use of the framework has been in developing visions and scenarios. Nearly all studies engaged with diverse values of nature through the framework’s fundamental value perspectives: ‘Nature for Society’, ‘Nature for Nature’, and ‘Nature as Culture/One with Nature’. While the framework is generally perceived as useful, challenges remain in integrating the NFF across multiple scales and fully incorporating plural values, particularly in measuring relational aspects and avoiding Western-centric biases. Future research priorities include developing integrated, quantitative studies and exploring transformative pathways to enhance the framework's effectiveness in driving sustainable outcomes. Overall, the growing body of work using the NFF provides a strong foundation for distilling best practices, facilitating large-scale applications, and achieving the framework's objectives
Regulations based on local realities
No full textTo ensure that management measures for marine areas and species are appropriate and properly applied, key stakeholders and local realities must be taken into account. New Caledonia's local authorities are experimenting with different approaches to tailor their environmental policies to the social and environmental challenges they are facin
Highlighting the resilience potential of marine protected areas in the face of coral bleaching with passive acoustic monitoring
No full textMarine Protected Areas (MPAs) can increase the resilience of reef communities to disturbances, playing a role in sheltering biodiversity from climate-related impacts. To determine if the protection status allows for better resilience after coral bleaching events, we recorded soundscapes of eight reefs of Moorea Island (French Polynesia). We compared the biophony of MPAs to the one of adjacent non-protected zones recorded in 2015, before two bleaching events (2016 and 2019), to the one in 2021. Then, the biophony from 2021 was compared within and outside MPAs. We hypothesize that differences in the biophony between these periods vary within and outside MPAs. The main result is an increase in the nocturnal high frequency (2–22 kHz) mass phenomena of benthic invertebrates, observed at sites with higher coral cover post-bleaching compared to pre-bleaching: nocturnal power spectral density (PSD) and peak frequency of invertebrate sounds varied between 2015 and 2021. For fish sounds, no daytime difference was observed, while nocturnal PSD was higher in 2021. These observations reflect distinct bleaching histories. High-frequency PSD measurements and the associated frequency values demonstrated strong correlation with temporal changes in coral cover. We suggest including it in long-term reef monitoring due to its complementary nature with respect to classical methods
Near-inertial wave trapping inside a fine-scale anticyclonic eddy during the BioSWOT-Med 2023 cruise: turbulence and energy flux
No full textNear-inertial waves (NIWs) are an important source of turbulence for the ocean interior. Mesoscale anticyclonic eddies are known to facilitate their propagation at depth while trapping them. However, in-situ observations have so far focused on large (>50 km radius), energetic eddies, whereas most of the ocean is populated by smaller, moderately energetic fine-scale structures. Are these smaller structures efficient to trap NIWs and enhance turbulence? Here, we present in-situ observations from the BioSWOT-Med 2023 cruise addressing this issue by surveying a fine-scale frontal area of the North Balearic front, assisted by the first high-resolution Sea Surface Height images of the new SWOT satellite mission during its Calibration/validation phase. We explore how fine scales modulate the evolution of turbulence below the mixed layer after experiencing two consecutive strong wind events. We show that turbulence remains low in the front and its cyclonic side, while being greatly enhanced in the anticyclonic side. The latter side is dominated by a fine-scale anticyclone (12.8 km of radius, Rossby number of 0.5) that trapped NIWs down to 300 m depth, increasing turbulent dissipation level to several 10-8 W/kg. Estimations of the NIW-induced vertical kinetic energy flux are about 1 to 10 times stronger than previous estimations outside and inside mesoscale anticyclones (5-10 mW/m2 vs 0.5-10 mW/m2). These results suggest that moderately energetic fine-scale structures are as important to structure flows and turbulence as large and intense structures found in western boundary currents and upwelling systems, addressing new challenges for their parameterization in Earth system models