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Matich, P., Kiszka, J. J., Heithaus, M. R., Le Bourg, B., & Mourier, J. (2019). Inter-individual differences in ontogenetic trophic shifts among three marine predators. Oecologia, 189(3), 621–636.
Résumé: Ontogenetic niche shifts are widespread. However, individual differences in size at birth, morphology, sex, and personalities can cause variability in behavior. As such, inherent inter-individual differences within populations may lead to context-dependent changes in behavior with animal body size, which is of concern for understanding population dynamics and optimizing ecological monitoring. Using stable carbon and nitrogen isotope values from concurrently sampled tissues, we quantified the direction and magnitude of intraspecific variation in trophic shifts among three shark species, and how these changed with body size: spurdogs (Squalus spp.) in deep-sea habitats off La Reunion, bull sharks (Carcharhinus leucas) in estuarine habitats of the Florida Everglades, and blacktip reef sharks (Carcharhinus melanopterus) in coral reef ecosystems of Moorea, French Polynesia. Intraspecific variation in trophic shifts was limited among spurdogs, and decreased with body size, while bull sharks exhibited greater individual differences in trophic shifts, but also decreased in variability through ontogeny. In contrast, blacktip reef sharks exhibited increased intraspecific variation in trophic interactions with body size. Variability in trophic interactions and ontogenetic shifts are known to be associated with changes in energetic requirements, but can vary with ecological context. Our results suggest that environmental stability may affect variability within populations, and ecosystems with greater spatial and/or temporal variability in environmental conditions, and those with more diverse food webs may facilitate greater individual differences in trophic interactions, and thus ontogenetic trophic shifts. In light of concerns over environmental disturbance, elucidating the contexts that promote or dampen phenotypic variability is invaluable for predicting population- and community-level responses to environmental changes.
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Mazurais, D., Covès, D., Papandroulakis, N., Ortega, A., Desbruyeres, E., Huelvan, C., et al. (2015). Gene expression pattern of digestive and antioxidant enzymes during the larval development of reared Atlantic bluefin tuna (ABFT), Thunnus thynnus L. Aquac Res, 46(10), 2323–2331.
Résumé: The aim of this study was to determine whether mortality observed during the larval development of reared bluefin tuna (Thunnus thynnus) could be related to improper expression profiles of key genes involved in digestive or antioxidant response capabilities. Tuna larvae were sampled at hatching, 2, 5, 10, 15 and 20 dph (days post hatching) for the relative quantification of transcripts encoded by genes involved in digestive [trypsinogen 1 (TRYP1), alpha-amylase (AMY), aminopeptidase N (ANPEP)] and antioxidant [catalase (CAT)] functions. The levels of expression of ANPEP related to the development and maturation of intestinal function increased from 5 to 20 dph. Furthermore, AMY and TRYP1 genes, which are pancreatic enzymes implicated in carbohydrate and peptide digestions exhibit a typical peak of expression at 5 and 15 dph respectively. The antioxidant enzyme, CAT, exhibited higher mRNA levels during the first stage of larval development. In conclusion, our investigation indicates that the expression of genes involved in digestive and antioxidant physiological processes followed typical patterns which could not explain high mortality rate observed during the first stage of larval development.
Mots-Clés: antioxidant; development; digestion; expression; gene; Tuna
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Pendleton, L. H., Ahmadia, G. N., Browman, H. I., Thurstan, R. H., Kaplan, D. M., & Bartolino, V. (2018). Debating the effectiveness of marine protected areas Introduction. ICES J. Mar. Sci., 75(3), 1156–1159.
Résumé: Increasing the size and number of marine protected areas (MPAs) is widely seen as a way to meet ambitious biodiversity and sustainable development goals. Yet, debate still exists on the effectiveness of MPAs in achieving ecological and societal objectives. Although the literature provides significant evidence of the ecological effects of MPAs within their boundaries, much remains to be learned about the ecological and social effects of MPAs on regional and seascape scales. Key to improving the effectiveness of MPAs, and ensuring that they achieve desired outcomes, will be better monitoring that includes ecological and social data collected inside and outside of MPAs. This can lead to more conclusive evidence about what is working, what is not, and why. Eight authors were asked to write about their experiences with MPA effectiveness. The authors were instructed to clearly define “effectiveness” and discuss the degree to which they felt MPAs had achieved or failed to be effective. Essays were exchanged among authors and each was invited to write a shorter “counterpoint.” The exercise shows that, while experiences are diverse, many authors found common ground regarding the role of MPAs in achieving conservation targets. This exchange of perspectives is intended to promote reflection, analysis, and dialogue as a means for improving MPA design, assessment, and integration with other conservation tools.
Mots-Clés: Aichi; benefits; conservation; fisheries; management; monitoring; reserves; shortfalls; spillover; sustainable development goals; targets
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Seddon, N., Mace, G. M., Naeem, S., Tobias, J. A., Pigot, A. L., Cavanagh, R., et al. (2016). Biodiversity in the Anthropocene: prospects and policy. Proc. R. Soc. B-Biol. Sci., 283(1844), 20162094.
Résumé: Meeting the ever-increasing needs of the Earth's human population without excessively reducing biological diversity is one of the greatest challenges facing humanity, suggesting that newapproaches to biodiversity conservation are required. One idea rapidly gaining momentum-as well as opposition-is to incorporate the values of biodiversity into decision-making using economic methods. Here, we develop several lines of argument for how biodiversity might be valued, building on recent developments in natural science, economics and science-policy processes. Then we provide a synoptic guide to the papers in this special feature, summarizing recent research advances relevant to biodiversity valuation and management. Current evidence suggests that more biodiverse systems have greater stability and resilience, and that by maximizing key components of biodiversity we maximize an ecosystem's long-term value. Moreover, many services and values arising from biodiversity are interdependent, and often poorly captured by standard economic models. We conclude that economic valuation approaches to biodiversity conservation should (i) account for interdependency and (ii) complement rather than replace traditional approaches. To identify possible solutions, we present a framework for understanding the foundational role of hard-to-quantify ` biodiversity services' in sustaining the value of ecosystems to humanity, and then use this framework to highlight new directions for pure and applied research. In most cases, clarifying the links between biodiversity and ecosystem services, and developing effective policy and practice for managing biodiversity, will require a genuinely interdisciplinary approach.
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Siegwalt, F., Benhamou, S., Girondot, M., Jeantet, L., Martin, J., Bonola, M., et al. (2020). High fidelity of sea turtles to their foraging grounds revealed by satellite tracking and capture-mark-recapture: New insights for the establishment of key marine conservation areas. Biol. Conserv., 250, 108742.
Résumé: Movement ecology studies are essential to protect highly mobile threatened species such as the green turtle (Chelonia mydas), classified as an endangered species by the IUCN. In 2019, the South Atlantic subpopulation has been downlisted to 'Least Concern', but the maintenance of this status strongly relies on the pursuit of research and conservation, especially on immatures, which contribute to the demographic renewal of this subpopulation. Identifying marine areas used by immatures is therefore crucial to implement efficient measures for the conservation of sea turtles in the Caribbean. We analysed data of capture-mark-recapture of 107 (out of 299) immatures recaptured at least once in Martinique, and satellite tracked 24 immatures to investigate their site fidelity and habitat use. Our results revealed a strong fidelity to foraging grounds, with mean residence times higher than 2 years, and with a high degree of affinity for specific areas within the coastal marine vegetation strip. Home ranges (95% kernel contour) and core areas (50% kernel contour) varied from 0.17 to 235.13 km(2) (mean +/- SD = 30.73 +/- 54.34 km(2)) and from 0.03 to 22.66 km(2) (mean +/- SD = 2.95 +/- 5.06 km(2)), respectively. Our findings shed light on a critical developmental area for immature green turtles in the French West Indies, and should help to refine Regional Management Units and reinforce the cooperative network aiming at ensuring conservation of the species at international scale.
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