Reproductive dynamics of swordfish (Xiphias gladius) in the southwestern Indian Ocean (Reunion Island). Part 1: oocyte development, sexual maturity and spawning Auteur(s) : Poisson, Francois Fauvel, Christian Éditeur(s) : EDP Sciences Résumé : The reproductive dynamics of swordfish (Xiphias gladius) was investigated from catches of the Reunion Island-based longline swordfish fishery between 19-25 degrees S and 48-54 degrees E. Thus, 1727 swordfish (size range 75-289 cm, lower jaw-to-fork length, LJFL) were sampled on board commercial fishing vessels during the period of May 1998 to January 2001. Reproductive activity was assessed using macroscopic gonad characteristics, trends of gonadal indexes for both sexes, oocyte size-frequency distributions and microscopic investigation of oocyte development stages. Size at first maturity (L-50) for female and male swordfish was estimated in Indian Ocean for the first time. L50 was estimated at 170 cm and 120 cm (LJFL) for females and males, respectively. Spawning occurred from October to April in the vicinity of Reunion Island where sex ratio of caught populations fluctuated seasonally. The seasonal changes in sex ratio and the incidence of larger individuals at the beginning of the spawning season provide some preliminary indications of synchronized movements of swordfish between spawning grounds and neighboring regions. Our results add significantly to knowledge about the reproductive biology of swordfish in the southwestern Indian Ocean. An overview of the available information on reproductive biology and dynamics of swordfish in Indian Ocean and eastern Pacific indicated that spawning activity is localized in discrete areas, and showed that there is incomplete information on spawning grounds in this extended area. La dynamique de la reproduction est étudiée chez des espadons (Xiphias gladius) capturés dans l'océan Indien, entre 1925 °Sud et 4854 °Est, par les palangriers de l'île de La Réunion. Ainsi, 1727 espadons de tailles comprises entre 75 et 289 cm (de l'extrémité de la mâchoire inférieure à la fourche caudale) ont été échantillonnés à bord de navires professionnels, de mai 1998 à janvier 2001. La reproduction est évaluée en analysant : les caractéristiques macroscopiques des gonades, l'évolution des indices gonadiques des deux sexes, les distributions de fréquence de taille des ovocytes et le développement des ovocytes au niveau microscopique. La taille à première maturité sexuelle (L50) des espadons de l'océan Indien est estimée pour la première fois ; elle atteint 170 cm pour les femelles et 120 cm pour les mâles. La saison de ponte s'étend d'octobre à avril aux abords de l'île tandis que le sexe-ratio fluctue de façon saisonnière. Les variations saisonnières du sexe-ratio et l'apparition de grands individus au début de la saison de ponte suggèrent des déplacements d'espadons entre cette zone de ponte et les régions voisines. Nos résultats apportent des informations fondamentales sur la biologie de la reproduction de l'espadon dans le sud-ouest de l'océan Indien. L'analyse de la bibliographie concernant biologie et la dynamique de la reproduction de l'espadon dans l'océan Indien et dans le Pacifique Est indique que l'activité de ponte est très localisée et que la connaissance des aires de pontes est encore incomplète dans cette région étendue. Aquatic Living Resources (0990-7440) (EDP Sciences), 2009 , Vol. 22 , N. 1 , P. 45-58 Droits : 2009 EDP Sciences http://archimer.ifremer.fr/doc/2009/publication-6353.pdf DOI:10.1051/alr/2009007 http://archimer.ifremer.fr/doc/00000/6353/ | Partager Voir aussi Indian Ocean Xiphias gladius Swordfish Seasonal distribution Size at first maturity Histology Spawning season Sex ratio Reproduction Télécharger |
Reproductive dynamics of swordfish (Xiphias gladius) in the southwestern Indian Ocean (Reunion Island). Part 2: fecundity and spawning pattern Auteur(s) : Poisson, Francois Fauvel, Christian Éditeur(s) : EDP Sciences Résumé : Batch fecundity and relative fecundity of swordfish (Xiphias gladius) in the southwestern Indian Ocean were estimated from seven gravid swordfish females (size range 127-225 cm lower jaw-to-fork length, LJFL) with unovulated, hydrated oocytes collected onboard Reunion-based (France) longline swordfish fishing vessels between December 1999 to January 2001. To investigate the spawning pattern of swordfish, we used data collected through a combination of two at sea sampling regimes. A total of 17 007 geo-located size data of swordfish were recorded during 8 years (1993-2001) and a total of 1727 (size range 75-289 cm, LJFL) swordfish gonads (1107 females and 620 males) were sampled from May 1998 to January 2001. The estimated batch fecundity ranged from 995 000 hydrated oocytes for the smallest ripe female to 4.3 millions for the largest female sampled measuring respectively 127 to 225 cm in curved length (LJFL). The relative fecundity ranged from 25 to 72 hydrated oocytes per gram of body weight. We found that batch fecundity was positively correlated with fish length and that the older/larger females have earlier and longer spawning seasons than younger/smaller females. These findings suggested that older/larger females which are seasonally migrating in this spawning ground seem to play a major role in reproductive success of the species in producing significantly more offspring than younger females during an extended spawning season. Examination of the length-frequency date from the fishery indicated that the young fish are resident around Reunion and around the seamounts off Reunion Island. Our results highlight the important role of the older/larger females in the reproductive capacity of southwestern Indian Ocean stock. We discuss the potential implications of fishing the older/larger females for this stock in terms of reproduction and recruitment. La fécondité par acte de ponte et la fécondité relative chez l'espadon (Xiphias gladius) dans le sud-ouest de l'océan Indien sont estimées d'après sept femelles de taille comprise entre 127 et 225 cm (de l'extrémité de la mâchoire inférieure à la fourche caudale) ; celles-ci ayant atteint la maturité sexuelle, les ovaires contenant des ovocytes hydratés. Ces femelles ont été pêchées entre décembre 1999 et janvier 2001, par des palangriers ciblant l'espadon et basés à La Réunion. La stratégie de la reproduction chez l'espadon a été étudiée en utilisant des données collectées au cours de deux campagnes d'échantillonnages en mer : soit 17 007 mensurations géo-référencées d'espadons, de 75 à 289 cm, qui ont été enregistrées durant les 8 années d'étude (1993-2001) et 1727 gonades d'espadon (1107 femelles et 620 mâles) prélevées entre mai 1998 et juin 2001.La fécondité par acte de ponte estimée varie de 995 000 ovocytes hydratés, pour la plus petite femelle (127 cm), à 4,3 millions pour la plus grande femelle (225 cm). La fécondité par acte de ponte est corrélée positivement à la taille du poisson. La fécondité relative s'étend de 25 à 72 ovocytes hydratés par gramme de poids de corps. Les femelles les plus âgées/grandes pondent plus tôt et sur une période plus grande que les plus jeunes/petites femelles. Ainsi, les femelles plus âgées/grandes qui migrent de façon saisonnière vers cette aire de ponte, contribueraient plus largement au renouvellement de l'espèce en produisant de façon significative davantage de recrues que les femelles plus jeunes et ceci pendant une saison de ponte plus étendue. Par ailleurs, les jeunes individus semblent séjourner aux abords de l'île de La Réunion et des monts sous-marins situés au large. Nos résultats soulignent l'importance du rôle des femelles âgées/grandes dans la capacité reproductrice du stock d'espadon du sud-ouest de l'océan Indien. Les implications potentielles de la pêche : des femelles âgées et de grandes tailles sont discutées pour ce stock, du point de vue de la reproduction et du recrutement. Aquatic Living Resources (0990-7440) (EDP Sciences), 2009 , Vol. 22 , N. 1 , P. 59-68 Droits : 2009 EDP Sciences http://archimer.ifremer.fr/doc/2009/publication-6354.pdf DOI:10.1051/alr/2009012 http://archimer.ifremer.fr/doc/00000/6354/ | Partager |
Genetic population structure of the Swordfish (Xiphias gladius) in the southwest Indian Ocean: Sex-biased differentiation, congruency between markers and its incidence in a way of stock assessment Auteur(s) : Muths, Delphine Grewe, R. Jean, Claire Bourjea, Jerome Éditeur(s) : Elsevier Résumé : Genetic variation was surveyed at 11 microsatellite loci and at 517 bp of the mitochondrial control region to investigate the presence of genetic stock structure in swordfish (Xiphias gladius) in four proximal localities of the southwest Indian Ocean. One aim of this study was to serve as a preliminary examination for congruency of structure detected by these two genetic markers, prior to conducting a more comprehensive basin-wide survey of the Indian Ocean and nearby surrounding areas. Analyses of multilocus microsatellite genotypes and mitochondrial control region sequences both revealed a great homogeneity between samples. Genetic diversity detected at the regional scale was not significantly higher than detected at the local scale. Results suggest that the southwest Indian Ocean globally functions as a unique panmictic population. However, some discrete genetic differences appeared that could possibly indicate influence from a second genetic pool in the northern part of the Indian Ocean. This structure appeared to be sex-dependent with genetic differences higher among female than among male samples. This result may indicate a higher level of spawning area fidelity for females with a subsequent sampling bias tending to homogenise male genotypic distributions. (c) 2009 Elsevier B.V. All rights reserved. Fisheries Research (0165-7836) (Elsevier), 2009-05 , Vol. 97 , N. 3 , P. 263-269 Droits : 2009 Elsevier B.V. All rights reserved. http://archimer.ifremer.fr/doc/2009/publication-6455.pdf DOI:10.1016/j.fishres.2009.03.004 http://archimer.ifremer.fr/doc/00000/6455/ | Partager |
Approche empirique de la pecherie d'espadon (Xiphias gladius) dans l'ocean Indien et modelisation des deplacements des poissons dans le paysage oceanique tropical Auteur(s) : Guyomard, David Éditeur(s) : Ecole Nationale Supérieure Agronomique de Rennes Résumé : Long-line fishing has been growing on the island of La Réunion since the beginning of the 1990s. The target species is the swordfish (Xiphias gladius), fished mainly in the tropical waters surrounding the island between longitudes 45 degree E and 60 degree E, and latitudes 17 degree S and 27 degree S. From 1998 to 2000, a finalised research programme enabled the collection of precise data concerning the lines' positions and the parameters of the fishing efforts: 3,602 nettings were thus informed by the catches (in numbers of individuals caught) and 12 descriptive variables of the effort. In parallel with this collection effort, satellite maps that described the ocean's landscape of this region of the Indian Ocean exploited by La Réunion's fisheries were made available to sailors and scientists. Extractions from these environmental variables were made at the fishing lines' positions, which allowed us to propose 20 variables describing the environmental conditions of swordfish catches applied to the nettings. In an early part of this study, after a descriptive analysis and a first selection of the variables, we used several GAM (Generalised Additive Models) to model the respective effects of effort and environmental variables on the variability of swordfish catches. We thus highlighted the predominance of factors linked to fishermen (fishing effort) on oceanographic factors in the explanation of this variability. Following these results, a summary on the biology and ecology of the swordfish was proposed in order to draw up hypotheses on the characteristics of this species' population in the Indian Ocean. The aspects linked to the individual behaviour and movements of the population were particularly highlighted. In a latter part of this study and in order to complete the empirical approach by an exploratory constructivist approach, we proposed a modelling tool in order to simulate the possible movements of individuals within the oceanic landscape described by the available satellite maps. After reading in the literature about the various forms of modelling the movements of the large pelagics, we developed an original computer modelling architecture of the multi-agent type that made it possible to manipulate in a dynamic way the satellite maps (and derived products), the individual movements of "animats" whose behaviours were based on this environmental information, and agents that clarify the process of long-line fishing in a geographical way. The computer model that was implemented (MUFINS, for MUlti-Fish INdian ocean Simulator) was next used by calibrating the behaviour of the animats on the real data originally from the analysis of commercial catches proposed in the first part, using robust techniques based on fuzzy logic. The results of the simulations were compared, on the one hand, with the large-scale hypotheses of movement proposed in the first part, and, on the other hand, to swordfish catches both real and corrected for the effect of the fishing effort modelled by the GAM models. Even if the results of these simulations in this study do not allow for proposing convincing interpretations of the underlying processes, the MUFINS tool showed its ability to address questions associated with the swordfish's behaviour in the tropical oceanic landscape and to the effects of scale transfers between the individual level and the collective level. We now envisage its use in a more operational framework, as an interface for dialogue between fishermen and scientists with a goal of sustainable management of the resource. La peche palangriere s'est developpee a l'ile de La Reunion depuis le debut des annees 1990. L'espece cible est l'espadon (Xiphias gladius), principalement exploite dans les eaux tropicales autour de l'ile entre les longitudes 45 degree E et 60 degree E, et les latitudes 17 degree S et 27 degree S. De 1998 a 2000, un programme de recherche finalisee a permis de collecter des informations precises concernant les positions des lignes et les parametres de l'effort de peche : 3602 filages sont ainsi renseignes par les captures (en nombre d'individus captures) et 12 variables descriptives de l'effort. En parallele de cet effort de collecte, des cartes satellitales ont pu etre mises a la disposition des marins et des scientifiques, decrivant le paysage oceanique de cette region de l'ocean Indien exploitee par la pecherie reunionnaise. Des extractions de ces variables environnementales ont ete effectuees aux positions des lignes de peche, nous permettant de proposer 20 variables descriptives des conditions environnementales de captures d'espadon appliquees aux filages. Dans une premiere partie de ce travail, apres une analyse descriptive et une premiere selection des variables, on a modelise par plusieurs modeles GAM (Generalized Additive Models) les effets respectifs des variables d'effort et des variables environnementales sur la variabilite des captures d'espadon. On a ainsi mis en evidence la predominance des facteurs lies aux pecheurs (effort de peche) sur les facteurs oceanographiques dans le caractere explicatif de cette variabilite. A la suite de ces resultats, une synthese sur la biologie et l'ecologie de l'espadon a ete proposee afin de degager des hypotheses sur les caracteristiques de la population de cette espece dans l'ocean Indien. Les aspects lies au comportement individuel et aux deplacements de la population ont ete particulierement mis en evidence. Dans une deuxieme partie de ce travail et afin de completer l'approche empirique par une approche constructiviste exploratoire, nous avons propose un outil de modelisation afin de simuler les deplacements possibles d'individus au sein du paysage oceanique decrit par les cartes satellitales disponibles. Apres avoir passe en revue dans la litterature les differentes formes de modelisation des deplacements des grands, pelagiques, nous avons developpe une architecture originale de modelisation informatique de type multi-agents permettant de manipuler de maniere dynamique les cartes satellitales (et les produits derives), les mouvements individuels < d'animats >, dont les comportements sont bases sur cette information environnementale, et des agents qui explicitent le processus de capture palangriere de maniere geographique. Le modele informatique ainsi implemente (MUFINS, pour MUlti-Fish INdian ocean Simulator) a ensuite ete utilise en calibrant les comportements des animats sur les donnees reelles issues de l'analyse des captures commerciales proposee en premiere partie, a partir de techniques robustes basee sur la logique floue. Les resultats des simulations ont ete confrontes d'une part aux hypotheses de deplacement a grande echelle proposees en premiere partie, et d'autre part aux captures d'espadon reelles et corrigees de l'effet de l'effort de peche modelise par les modeles GAM. Meme si les resultats de simulations presentes dans ce travail ne permettent pas de proposer d'interpretations convaincantes des processus sous-jacents, l'outil MUFINS a demontre son aptitude a aborder les questions liees au comportement de l'espadon dans le paysage oceanique tropical et aux effets des transferts d'echelle entre le niveau individuel et le niveau collectif. On envisage desormais son utilisation dans un cadre plus operationnel, comme interface de dialogue entre les pecheurs et les scientifiques a des fins de gestion durable de la ressource. Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/2005/these-2592.pdf http://archimer.ifremer.fr/doc/00000/2592/ | Partager |
Mercury content in commercial pelagic fish and its risk assessment in the Western Indian Ocean Auteur(s) : Kojadinovic, Jessica Potier, M Le Corre, M Cosson, R Bustamante, Paco Éditeur(s) : Elsevier Résumé : As top predators of pelagic food webs, large fish naturally bioaccumulate mercury (Hg). Determining Hg burdens in commercialized fish is essential considering the concern about effects of contaminants on human health and the legal thresholds that are therefore set for local consumption and/or exportation. Total Hg levels were measured in the muscular tissue of 183 fish of five commercially important species from the tropical zone of the Western Indian Ocean. All individuals were measured and sexed in order to study the impregnation of Hg with size and sex within each species. Values of Hg found in this part of the Indian Ocean were comparable to Hg in muscular tissue of the same species studied in other areas. The highest Hg levels were noted in Swordfish (Xiphias gladius) caught in waters surrounding Reunion Island (3.97 +/- 2.67 mu g g(-1) dry weight). Following the Swordfish, in decreasing order of Hg content, were the Yellowfin Tuna (Thunnus albacares) and the Skipjack (Katsuwonus pelamis), then the Common Dolphinfish (Coryphaena hippurus) and the Wahoo (Acanthocybium solandri). In the North of the Mozambique Channel, Swordfish had higher Hg levels than Yellowfin Tunas, and Dolphinfish exhibited intermediate Hg levels. The size of a fish was a determining factor of its Hg burden, as was the species. Differences in size-normalized Hg levels were observed between the two study zones for Swordfish and Common Dolphinfish. Sex, in contrast, did not influence Hg levels suggesting that females and males have similar feeding habits. The muscular Hg levels presented here suggest that consumers of fish originating from the Western Indian Ocean should limit themselves to one Swordfish based meal per week, or one fish meal a day if they choose to eat tuna or Common Dolphinfish. (c) 2006 Elsevier B.V. All rights reserved. The Science of The Total Environment (0048-9697) (Elsevier), 2006-08 , Vol. 366 , N. 2-3 , P. 688-700 Droits : 2006 Elsevier http://archimer.ifremer.fr/doc/2006/publication-1862.pdf DOI:10.1016/j.scitotenv.2006.02.006 http://archimer.ifremer.fr/doc/00000/1862/ | Partager Voir aussi Health standards Mozambique channel Reunion Island Pelagic fish Impregnation levels Mercury Télécharger |
Diversifying fishing effort in Sicilian fisheries: the case of Fish Aggregating Devices (FADs) Auteur(s) : Cannizzaro, L Bono, G Rizzo, P Potoshi, A Celesti, A Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999 Résumé : In the Sicilian fisheries, the swordfish (Xiphias gladius, Linnaeus 1758), caught from March to December with several gears which vary according to season, represents one of the most important economic resources. The size composition changes depending on the gear used, the way it is operated, the fishing area and season. The gears used for swordfish fishing (long-lines "for swordfish", drift-nets, harpoons as operated by typical boats named "feluche") mainly catch adult specimens. From August to December, a high number of very young swordfish specimens (1.5 to 4.5 kg) is also caught as by-catch during the albacore (Thunnus alalunga, Bonnaterre 1788) fishing which is carried out by a special long line and hooks only 3 cm long. It was observed that in the same season, fishing areas and with boats of similar type, the fishing of dolphin-fish (Coryphaena hippurus, Linnaeus 1758), using Fish Aggregating Devices (FADs) and purse seine, is hardly practised in spite of the resource availability swordfish. With the present work, which can be regarded as an initial approach to the problem of diversifying and managing fishing effort of swordfish, albacore and dolphin-fish, their fisheries are examined and discussed, not overlooking the economic aspect, by considering weather a reallocation of fishing effort among the previously said resources might avert the risk of swordfish stock depletion. Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/00042/15299/12659.pdf http://archimer.ifremer.fr/doc/00042/15299/ | Partager Voir aussi Attracting techniques Fishing effort Tuna fisheries Article Geographic Terms: MED, Italy, Sicilia Télécharger |
Technique de pêche à la Palangre du Requin Sonneur (Lamna nasus Bonnaterre) et de l'Espadon (Xiphias gladius Linnaeus) en Atlantique Nord-Est Auteur(s) : Le Gall, Jean-yves Mallet, G. Éditeur(s) : Société franco-japonaise d'océanographie Résumé : French fishermen have been fishing porbeagle shark Lamna nasus on the edges of the continental shelf, from the Bay of Biscay to the south of Ireland. Incidentally, until the past few years, when, during summer, bluefin tunas Thunnus thynnus, albacores Thunnus alalunga and sworfishes Xiphias gladius were caught on the same line. Since 1970, some fishermen have started focusing on swordfish. The authors describe the technique and gear used for this fishery. A fishery that could largely develop in the years to come. Les pêcheurs artisans français pêchent depuis une vingtaine d'années le requin sonneur (ou taupe) Lamna nasus sur les accores du plateau continental du Colfe de Gascogne jusqu'au Sud de l'Irlande. Incidemment jusqu'à ces dernières annees, durant l'été, des thons rouges Thunnus thynnus, des germons Thunnus alalunga et des espadons Xiphias gladius étaient capturés A l'aide de cette même palangre. Depuis 1970, quelques pêcheurs commencent à développer un effort de pêche particulier pour la capture de l'espadon. Les auteurs décrivent la technique et les engins de cette pêche qui peut se développer beaucoup plus largement dans les années à venir. [OCR NON CONTRÔLE] Bulletin de la Société franco-japonaise d'océanographie (Société franco-japonaise d'océanographie), 1972-11 , Vol. 10 , N. 4 , P. 174-177 Droits : Société franco-japonaise d'océanographie http://archimer.ifremer.fr/doc/1972/publication-5140.pdf http://archimer.ifremer.fr/doc/00000/5140/ | Partager |
Patterns of variations in large pelagic fish: A comparative approach between the Indian and the Atlantic Oceans Auteur(s) : Corbineau, A. Rouyer, Tristan Fromentin, Jean-marc Cazelles, B. Fonteneau, Alain Menard, Frederic Éditeur(s) : Pergamon-elsevier Science Ltd Résumé : Catch data of large pelagic fish such as tuna, swordfish and billfish are highly variable ranging from short to long term. Based on fisheries data, these time series are noisy and reflect mixed information on exploitation (targeting, strategy, fishing power), population dynamics (recruitment, growth, mortality, migration, etc.), and environmental forcing (local conditions or dominant climate patterns). In this work, we investigated patterns of variation of large pelagic fish (i.e. yellowfin tuna, bigeye tuna, swordfish and blue marlin) in Japanese longliners catch data from 1960 to 2004. We performed wavelet analyses on the yearly time series of each fish species in each biogeographic province of the tropical Indian and Atlantic Oceans. In addition, we carried out cross-wavelet analyses between these biological time series and a large-scale climatic index, i.e. the Southern Oscillation Index (Sol). Results showed that the biogeographic province was the most important factor structuring the patterns of variability of Japanese catch time series. Relationships between the SOI and the fish catches in the Indian and Atlantic Oceans also pointed out the role of climatic variability for structuring patterns of variation of catch time series. This work finally confirmed that Japanese longline CPUE data poorly reflect the underlying population dynamics of tunas. (C) 2010 Elsevier Ltd. All rights reserved. Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2010-07 , Vol. 86 , N. 1-2 , P. 276-282 Droits : 2010 Elsevier B.V. All rights reserved. http://archimer.ifremer.fr/doc/00011/12231/9029.pdf DOI:10.1016/j.pocean.2010.04.019 http://archimer.ifremer.fr/doc/00011/12231/ | Partager |
Country report reunion swordfish fishery (France) Auteur(s) : Poisson, Francois Taquet, Marc Éditeur(s) : IOTC Proceedings, 2001, n° 4, pp 144-154 (WPB01-07) Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/00129/24046/22008.pdf http://archimer.ifremer.fr/doc/00129/24046/22012.pdf http://archimer.ifremer.fr/doc/00129/24046/ | Partager |
French swordfish longline fishery in south west Indian Ocean: preliminary results from the PPR program Auteur(s) : Poisson, Francois Taquet, Marc Éditeur(s) : IOTC Proceedings, 2000, n° 3, pp 169-201 (WPB00-06) Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/00130/24080/22054.pdf http://archimer.ifremer.fr/doc/00130/24080/22055.pdf http://archimer.ifremer.fr/doc/00130/24080/ | Partager |