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Suquet, M., Cosson, J., Donval, A., Labbe, C., Boulais, M., Haffray, P., et al. (2012). Marathon vs sprint racers: an adaptation of sperm characteristics to the reproductive strategy of Pacific oyster, turbot and seabass. J. Appl. Ichthyol., 28(6), 956–960.
Résumé: This work assesses the present knowledge on Pacific oyster sperm biology in comparison to two marine fish species (turbot and seabass) whose sperm characteristics are well described. Sperm morphology mainly differs by the presence of an acrosome in Pacific oyster which is absent in both fish species. In turbot as in Pacific oyster, a sperm maturation process along the genital tract is observed. Sperm motility is triggered by changes in osmolality for seabass and turbot and in pH for Pacific oyster. However, complementary factors are involved to maintain sperm immotile in the genital tract. Sperm movement duration is very long in Pacific oyster (2024 h), compared to turbot (35 min) and seabass (4050 s). A high capacity of ATP regeneration is observed in Pacific oyster sperm, sustained by the limited changes in its morphology observed at the end of the swimming phase. Then, the total distance covered by spermatozoa is very different among the studied species (seabass: 2 mm, turbot: 12 mm, Pacific oyster: 1 m). Considering the main characteristics of sperm movement, the three studied species can be separated in two groups: the sprint racer group (seabass: high velocity and short distance covered) and the marathonian racer one (Pacific oyster: low velocity but covering long distances). To an intermediate extent, turbot sperm belongs to the sprint racer group. Then, the two different sperm movement strategies observed in the three species, are compensated by the behaviour of the breeders.
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Rossi, F., Colao, E., Martinez, M. J., Klein, J. C., Carcaillet, F., Callier, M. D., et al. (2013). Spatial distribution and nutritional requirements of the endosymbiont-bearing bivalve Loripes lacteus (sensu Poli, 1791) in a Mediterranean Nanozostera noltii (Hornemann) meadow. Journal of Experimental Marine Biology and Ecology, 440, 108–115.
Résumé: Sulphur-oxidising endosymbiont-bearing bivalves often inhabit seagrass meadows, where they can control sulphide levels and variably contribute to carbon cycling, by feeding on endosymbiotic bacteria and/or on particulate organic matter from the water column. The patterns of variability in their feeding mode and their spatial distribution within the seagrass meadows are however poorly studied. Seagrass beds form naturally patchy habitats with seagrass-sand edges that may have variable effects on different organisms. The present study aims at understanding differences in feeding mode and abundance of the endosymbiont-bearing bivalve Loripes lacteus (sensu Poli, 1791) as well as the physiological conditions of its endosymbiotic populations between edge and inner portion of meadows of the eelgrass Nanozostera noltii (Hornemann). In July 2010, Loripes specimens were sampled in 4 eelgrass patches at 2 different locations in the Thau lagoon, South of France. There was a clear negative edge effect on the abundance of small individuals of Loripes, while large individuals were homogeneously distributed between edge and inner part of the meadow. Although Loripes isotopic signatures (delta C-13 and delta N-15) were always closer to those of its symbiotic bacteria than to those of suspension-feeding bivalves, eelgrass edge enhanced mixotrophic behaviour of small animals, which assimilated less bacterial carbon and nitrogen at the edge than in the inner part of the eelgrass meadow. No differences related to eelgrass edges were instead found for the bacterial populations harboured by Loripes. Rather, flow cytometry revealed large variability at small spatial scales. Although bacteria were always important for the nutrition of Loripes, these findings showed that seagrass edges may contribute to regulate feeding mode and population structure of Loripes, which may have implications for seagrass functioning. (C) 2012 Elsevier B.V. All rights reserved.
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Lassalle, G., Gascuel, D., Loc'h, F. L., Lobry, J., Pierce, G. J., Ridoux, V., et al. (2012). An ecosystem approach for the assessment of fisheries impacts on marine top predators : the Bay of Biscay case study. Ices Journal of Marine Science, 69(6), 925–938.
Résumé: A number of marine mammal populations is currently threatened by their interactions with fisheries. The present study aimed to provide insights into the severity of potential impacts of operational and biological interactions between top predators and fisheries, in the Bay of Biscay region. Our approach was to modify an Ecopath with Ecosim (EwE) model describing the overall structure and function of the ecosystem by including landings and discards of exploited stocks and estimations of the bycatch of non-target compartments. Second, a set of ecological indices and a trophic level (TL)-based model (EcoTroph, ET) were derived from the EwE model. ET was used to simulate the effects of increasing fishing pressure on the ecosystem and, more particularly, on top predators. The Bay of Biscay was demonstrated to be not far from overexploitation at the current fishing rate, this phenomenon being particularly noticeable for the highest TLs. Within the toothed cetacean community, bottlenose dolphins appeared the most sensitive to resource depletion, whereas common dolphins and harbour porpoises were most impacted by their incidental captures in fishing gears. This study provides a methodological framework to assess the impacts of fisheries on ecosystems for which EwE, or other ecosystem models, already exist.
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Marinesque, S., Kaplan, D., & Rodwell, L. D. (2012). Global implementation of marine protected areas : is the developing world being left behind ? Marine Policy, 36(3), 727–737.
Résumé: While the global network of marine protected areas (MPAs) has recently been evaluated in the light of bio-geographic targets, there has been no attempt to evaluate the relative conservation efforts made by the different nations with regards to their level of socio-economic development. Using information mostly gathered from the world database on protected areas (WDPA), this paper gives a comparative assessment of MPA progress in countries from different economic categories, ranging from advanced economies to least developed countries (LDCs). Potentially explanatory socio-economic and environmental factors, such as fishing activity and existence of vulnerable marine ecosystems, for variability between nations in the level of MPA implementation are also explored. Existing MPA databases demonstrate a clear gap between developed and developing nations in MPA establishment, with advanced economies accounting for two thirds of the global MPA network. Patterns of MPA use, however, remain extremely heterogeneous between countries within each development group. International agreements on marine conservation, above and beyond the influence of country socioeconomic and environmental profiles, are identified as a stimulating factor to MPA implementation. The level dependence on marine resource extraction appears to impede MPA implementation, though the relationship is not statistically significant due to large heterogeneity among countries. Leading developed nations increasingly use MPAs to designate integrated and adaptive management areas, and implementation of large “no-take” reserves in relatively-pristine overseas areas continues to accelerate. These analyses highlight certain limitations regarding our ability to assess the true conservation effectiveness of the existing global MPA network and the need for improved indicators of MPA restrictions and management efforts.
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Grehan, A. J., Arnaud-Haond, S., D'Onghia, G., Savini, A., & Yesson, C. (2017). Towards ecosystem based management and monitoring of the deep Mediterranean, North-East Atlantic and Beyond. Deep-Sea Res. Part II-Top. Stud. Oceanogr., 145, 1–7.
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