Can fisheries-induced evolution shift reference points for fisheries management? Auteur(s) : Heino, Mikko Baulier, Loic Boukal, David S. Ernande, Bruno Johnston, Fiona D. Mollet, Fabian M. Pardoe, Heidi Therkildsen, Nina O. Éditeur(s) : Oxford Univ Press Résumé : Biological reference points are important tools for fisheries management. Reference points are not static, butmay change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to "shifting" reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in "true" reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in more perilous directions, such that actual risks are greater than anticipated. Our qualitative analysis suggests that all commonly used reference points are susceptible to shifting through fisheries-induced evolution, including the limit and "precautionary" reference points for spawning-stock biomass, B-lim and B-pa, and the target reference point for fishing mortality, F-0.1. Our findings call for increased awareness of fisheries-induced changes and highlight the value of always basing reference points on adequately updated information, to capture all changes in the biological processes that drive fish population dynamics. Ices Journal Of Marine Science (1054-3139) (Oxford Univ Press), 2013-07 , Vol. 70 , N. 4 , P. 707-721 Droits : 2013 International Council for the Exploration of the Sea. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com http://archimer.ifremer.fr/doc/00151/26228/24302.pdf DOI:10.1093/icesjms/fst077 http://archimer.ifremer.fr/doc/00151/26228/ | Partager |
Effects of Oceanic Salinity on Body Condition in Sea Snakes Auteur(s) : Brischoux, Francois Rolland, Virginie Bonnet, Xavier Caillaud, Matthieu Shine, Richard Éditeur(s) : Oxford Univ Press Inc Résumé : Since the transition from terrestrial to marine environments poses strong osmoregulatory and energetic challenges, temporal and spatial fluctuations in oceanic salinity might influence salt and water balance (and hence, body condition) in marine tetrapods. We assessed the effects of salinity on three species of sea snakes studied by mark-recapture in coral-reef habitats in the Neo-Caledonian Lagoon. These three species include one fully aquatic hydrophiine (Emydocephalus annulatus), one primarily aquatic laticaudine (Laticauda laticaudata), and one frequently terrestrial laticaudine (Laticauda saintgironsi). We explored how oceanic salinity affected the snakes' body condition across various temporal and spatial scales relevant to each species' ecology, using linear mixed models and multimodel inference. Mean annual salinity exerted a consistent and negative effect on the body condition of all three snake species. The most terrestrial taxon (L. saintgironsi) was sensitive to salinity over a short temporal scale, corresponding to the duration of a typical marine foraging trip for this species. In contrast, links between oceanic salinity and body condition in the fully aquatic E. annulatus and the highly aquatic L. laticaudata were strongest at a long-term (annual) scale. The sophisticated salt-excreting systems of sea snakes allow them to exploit marine environments, but do not completely overcome the osmoregulatory challenges posed by oceanic conditions. Future studies could usefully explore such effects in other secondarily marine taxa such as seabirds, turtles, and marine mammals. Integrative And Comparative Biology (1540-7063) (Oxford Univ Press Inc), 2012-08 , Vol. 52 , N. 2 , P. 235-244 Droits : The Author 2012. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. http://archimer.ifremer.fr/doc/00089/20064/20739.pdf DOI:10.1093/icb/ics081 http://archimer.ifremer.fr/doc/00089/20064/ | Partager |
The Protist Ribosomal Reference database (PR2): a catalog of unicellular eukaryote Small Sub-Unit rRNA sequences with curated taxonomy Auteur(s) : Guillou, Laure Bachar, Dipankar Audic, S Bass, David Berney, Cedric Bittner, Lucie Boutte, Christophe Burgaud, Gaetan Éditeur(s) : Oxford Univ Press Résumé : The interrogation of genetic markers in environmental meta-barcoding studies is currently seriously hindered by the lack of taxonomically curated reference data sets for the targeted genes. The Protist Ribosomal Reference database (PR2, http://ssurrna. org/) provides a unique access to eukaryotic small sub-unit (SSU) ribosomal RNA and DNA sequences, with curated taxonomy. The database mainly consists of nuclear-encoded protistan sequences. However, metazoans, land plants, macrosporic fungi and eukaryotic organelles (mitochondrion, plastid and others) are also included because they are useful for the analysis of hightroughput sequencing data sets. Introns and putative chimeric sequences have been also carefully checked. Taxonomic assignation of sequences consists of eight unique taxonomic fields. In total, 136 866 sequences are nuclear encoded, 45 708 (36 501 mitochondrial and 9657 chloroplastic) are from organelles, the remaining being putative chimeric sequences. The website allows the users to download sequences from the entire and partial databases (including representative sequences after clustering at a given level of similarity). Different web tools also allow searches by sequence similarity. The presence of both rRNA and rDNA sequences, taking into account introns (crucial for eukaryotic sequences), a normalized eight terms ranked-taxonomy and updates of new GenBank releases were made possible by a long-term collaboration between experts in taxonomy and computer scientists. Nucleic Acids Research (0305-1048) (Oxford Univ Press), 2013-01 , Vol. 41 , N. D1 , P. D597-D604 Droits : The Author(s) 2012. Published by Oxford University Press. http://archimer.ifremer.fr/doc/00114/22492/20174.pdf DOI:10.1093/nar/gks1160 http://archimer.ifremer.fr/doc/00114/22492/ | Partager |
Combining sensitivity and uncertainty analysis to evaluate the impact of management measures with ISIS-Fish: marine protected areas for the Bay of Biscay anchovy (Engraulis encrasicolus) fishery Auteur(s) : Lehuta, Sigrid Mahevas, Stephanie Petitgas, Pierre Pelletier, Dominique Éditeur(s) : Oxford Univ Press Résumé : Spatio-seasonal explicit simulation models can predict the impact of spatial management measures on marine fish populations and fishing activities. As fisheries are complex systems, fisheries simulation models are often complex, with many uncertain parameters. Here, the methodology is provided to deliver fishery diagnostics within an uncertainty context using a complex simulation tool. A sensitivity analysis of the model is performed on model outputs using partial least-squares to identify the most sensitive parameters. The impact of several management measures is then simulated using a statistical simulation design taking into account the uncertainty of the selected sensitive parameters. This approach was applied to the Bay of Biscay anchovy stock using the ISIS-Fish (Integration of Spatial Information for Simulation of Fisheries) model to assess the impact of imposing marine protected areas (MPAs) conditionally on parameter uncertainty. The diagnostic appeared to be highly sensitive to the mortality of larvae and juveniles, growth, and reproduction. The uncertainty of the values of these parameters did not permit any of the simulated MPA designs to be proposed. However, according to anchovy catch and biomass, the simulations allowed the low impact of closure duration to be shown and underscored the utility of protecting such key processes as spawning. Ices Journal Of Marine Science (1054-3139) (Oxford Univ Press), 2010-07 , Vol. 67 , N. 5 , P. 1063-1075 Droits : 2010 ICES/CIEM. Oxford journals http://archimer.ifremer.fr/doc/00011/12234/9281.pdf DOI:10.1093/icesjms/fsq002 http://archimer.ifremer.fr/doc/00011/12234/ | Partager Voir aussi Bay of Biscay anchovy marine protected area sensitivity analysis simulation uncertainty analysis Télécharger |
Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration Auteur(s) : Mihoubi, A. Schnurle, Philippe Benaissa, Z. Badsi, M. Bracene, R. Djelit, H. Geli, Louis Sage, F. Éditeur(s) : Oxford Univ Press Résumé : This study presents the results of a deep seismic survey across the north Algerian margin, based on the combination of 2-D multichannel and wide-angle seismic data simultaneously recorded by 41 ocean bottom seismometers deployed along a north-south line extending 180 km off Jijel into the Algerian offshore basin, and 25 land stations deployed along a 100-km-long line, cutting through the Lesser Kabylia and the Tellian thrust-belt. The final model obtained using forward modelling of the wide-angle data and pre-stack depth migration of the seismic reflection data provides an unprecedented view of the sedimentary and crustal structure of the margin. The sedimentary layers in the Algerian basin are 3.75 km thick to the north and up to 4.5-5 km thick at the foot of the margin. They are characterized by seismic velocities from 1.9 to 3.8 km s(-1). Messinian salt formations are about 1 km thick in the study area, and are modelled and imaged using a velocity between 3.7 and 3.8 km s(-1). The crust in the deep sea basin is about 4.5 km thick and of oceanic origin, presenting two distinct layers with a high gradient upper crust (4.7-6.1 km s(-1)) and a low gradient lower crust (6.2-7.1 km s(-1)). The upper-mantle velocity is constrained to 7.9 km s(-1). The ocean-continent transition zone is very narrow between 15 and 20 km wide. The continental crust reaches 25 km thickness as imaged from the most landward station and thins to 5 km over a less than 70 km distance. The continental crust presents steep and asymmetric upper- and lower-crustal geometry, possibly due to either asymmetric rifting of the margin, an underplated body, or flow of lower crustal material towards the ocean basin. Present-time deformation, as imaged from three additional seismic profiles, is characterized by an interplay of gravity-driven mobile-salt creep and active thrusting at the foot of the tectonically inverted Algerian margin. Geophysical Journal International (0956-540X) (Oxford Univ Press), 2014-09 , Vol. 198 , N. 3 , P. 1486-1503 Droits : 2014 The Royal Astronomical Society http://archimer.ifremer.fr/doc/00217/32836/32150.pdf DOI:10.1093/gji/ggu179 http://archimer.ifremer.fr/doc/00217/32836/ | Partager |
Martinique: a Clear Case for Sediment Melting and Slab Dehydration as a Function of Distance to the Trench Auteur(s) : Labanieh, Shasa Chauvel, Catherine Germa, Aurelie Quidelleur, Xavier Éditeur(s) : Oxford Univ Press Résumé : In subduction zones, melting and dehydration of the subducted slab introduce material into the mantle wedge and modify its chemical and isotopic composition. As a consequence, island arc lavas differ significantly from mid-ocean ridge basalts and ocean island basalts. In some arcs, the composition of lavas is strongly influenced by the sedimentary material introduced with the slab; in others, magma composition is mainly affected by aqueous fluids released by the slab. The Lesser Antilles arc is known for its extreme continental-crust-like signature but for some Lesser Antilles lavas subducted sediments are barely involved and enrichment in fluid-mobile elements (Ba, U, Sr, Pb, etc.) is the dominant feature. Here we evaluate whether La/Sm is a quantitative proxy of sediment involvement in volcanic arcs, and we relate dehydration and melting processes to the temperature and pressure conditions of the slab. We use Martinique as a case study because in this island both dehydration and sediment melting fingerprints coexist. We measured major and trace elements for about 130 age-constrained samples, carefully chosen to cover all volcanic phases of Martinique (25 Ma to present). Using these results we demonstrate that: (1) weathering does not modify the La/Sm ratio; (2) fractional crystallization of amphibole and/or garnet does not increase La/Sm by more than 20%; (3) rare earth element transfer from wall-rock to magma during fractionation is not significant; (4) melting of the mantle source increases La/Sm by only about 20%. As a consequence, we show that the proportion of slab sediment incorporated in the mantle wedge controls the La/Sm ratio of the source. The observed correlations between La/Sm and Nd and Hf isotopic compositions indicate that the effect of sediment addition is the overwhelming factor: La/Sm is a good proxy for slab sediment proportion in Martinique. We observe a geographical gradient between slab dehydration and sediment melting on the island. Whereas lavas located on the western side of the island display a clear sedimentary input in their source, lavas located on the eastern side of the island, closer to the trench, are clearly influenced by dehydration of the subducted slab. In addition, the aqueous fluids clearly come from the subducted basalt and they did not interact with the overlying sediments. The influence of sediment added to the source of the magmas increases from the eastern part to the western part of the island. We relate this geographical change to the pressure and temperature conditions at the slab surface. Sediments probably cross their solidus under Martinique and hydrous melting is triggered. Finally, we show that under all volcanic arcs where the signature of sediments overwhelms the signature of fluids, the slab surface reaches P-T conditions that allow the subducted sediments to melt. Inversely, under most volcanic arcs where the signal of aqueous fluids dominates over sediment melts, the subducted slab is not hot enough for the sedimentary pile to melt. Journal Of Petrology (0022-3530) (Oxford Univ Press), 2012-12 , Vol. 53 , N. 12 , P. 2441-2464 Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/00113/22392/20234.pdf DOI:10.1093/petrology/egs055 http://archimer.ifremer.fr/doc/00113/22392/ | Partager |
An investigation of human vs. technology-induced variation in catchability for a selection of European fishing fleets Auteur(s) : Mahevas, Stephanie Vermard, Youen Hutton, Trevor Iriondo, Ane Jadaud, Angelique Maravelias, Christos D. Punzon, Antonio Sacchi, Jacques Éditeur(s) : Oxford Univ Press Résumé : The impact of the fishing effort exerted by a vessel on a population depends on catchability, which depends on population accessibility and fishing power. The work investigated whether the variation in fishing power could be the result of the technical characteristics of a vessel and/or its gear or whether it is a reflection of inter-vessel differences not accounted for by the technical attributes. These inter-vessel differences could be indicative of a skipper/crew experience effect. To improve understanding of the relationships, landings per unit effort (lpue) from logbooks and technical information on vessels and gears (collected during interviews) were used to identify variables that explained variations in fishing power. The analysis was undertaken by applying a combination of generalized additive models and generalized linear models to data from several European fleets. The study highlights the fact that taking into account information that is not routinely collected, e. g. length of headline, weight of otter boards, or type of groundrope, will significantly improve the modelled relationships between lpue and the variables that measure relative fishing power. The magnitude of the skipper/crew experience effect was weaker than the technical effect of the vessel and/or its gear. Ices Journal Of Marine Science (1054-3139) (Oxford Univ Press), 2011-11 , Vol. 68 , N. 10 , P. 2252-2263 Droits : 2011 International Council for the Exploration of the Sea. Published by Oxford University Press. All rights reserved. http://archimer.ifremer.fr/doc/00049/16043/15172.pdf DOI:10.1093/icesjms/fsr150 http://archimer.ifremer.fr/doc/00049/16043/ | Partager |