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Auteur Peraltilla, S.; Bertrand, S.
Titre In situ measurements of the speed of Peruvian anchovy schools Type Article scientifique
Année 2014 Publication Revue Abrégée (up) Fisheries Research
Volume 149 Numéro Pages 92-94
Mots-Clés Multibeam sonar; Peruvian anchovy; School speed
Résumé While speed of fish schools is critical information for parameterizing numerous ecosystem models and evaluating fishery management options, it is poorly documented. Here we present results of in situ measurements of the speed of Peruvian anchovy schools, a small pelagic species that sustain the world's largest mono-specific fishery. Instantaneous school speed was in average 0.6 ms(-1), authorizing theoretical maximum displacements of similar to 26 km day(-1).
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ISSN 0165-7836 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 331
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Auteur Torres-Irineo, E.; Gaertner, D.; Chassot, E.; Dreyfus-Leon, M.
Titre Changes in fishing power and fishing strategies driven by newtechnologies : the case of tropical tuna purse seiners in the easternAtlantic Ocean Type Article scientifique
Année 2014 Publication Revue Abrégée (up) Fisheries Research
Volume 155 Numéro Pages 10-19
Mots-Clés
Résumé Technological advancements can influence both the fishing power of a fleet and the fishing strategies itemploys. To investigate these potential linkages, we examined almost three decades of data (1981&8211;2008)from French tropical tuna purse seiners operating in the eastern Atlantic Ocean. Applying a sequence ofstatistical methods at different temporal and spatial scales, we analyzed two indicators of fishing power(sets per boat-day on fish aggregating devices (FADs) and sets per boat-day on free-swimming schools)each of which represent a distinct fishing mode. Our results show that the increasing modernizationof this fleet has led to increases in both fishing power and the available number of fishing strategies tochoose from. A key output of this analysis was the breakdown of fishing power time series (for each fishingmode) into separate periods of continuous years during which catchability was assumed to be constant,thus identifying regime shifts. This partitioning allowed us to identify when key changes occurred inthe fishery. Changes in FAD-associated fishing were mostly driven by the introduction of radio beacons(early 1990s) which lead to an increase in fishing effort and an expansion of fishing grounds (directeffect) and the implementation of time-area management measures which resulted in a fragmentationof the traditional fishing grounds in the 2000s (indirect effect). During the same period, fishing on free-swimming schools also increased despite the biomass of stocks decreasing and fishing grounds remainingunchanged. This suggests these increases were driven by improvements in fish detection technology (e.g.,bird radars, sonar). These identified increases are not entirely unexpected: indeed it is widely recognizedthat fishing power in the purse seine tuna fishery has increased over time. However, these increases donot necessarily occur linearly. Thus, understanding how fishing power is changing over time (such asdetermining when regime shifts occur) is critical to improving the CPUE standardization procedure intropical tuna purse seine fisheries.
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Numéro d'Appel LL @ pixluser @ collection 335
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Auteur Grande, M.; Murua, H.; Zudaire, I.; Goni, N.; Bodin, N.
Titre Reproductive timing and reproductive capacity of the Skipjack Tuna (Katsuwonus pelamis) in the western Indian Ocean Type Article scientifique
Année 2014 Publication Revue Abrégée (up) Fisheries Research
Volume 156 Numéro Pages 14-22
Mots-Clés Condition; Gonadosomatic index; Oocyte; Reproductive capacity; Spawning season
Résumé We studied the sexual maturity, batch fecundity and spawning season of the Skipjack Tuna Katsuwonus pelamis. Generalized additive modelling was applied to assess the effect of demographic features on ovary growth. During 2009 and 2010, 673 females were caught on board a purse-seine fishing vessel in the western Indian Ocean. Fish were classified into different reproductive phases and this information was used to determine the size at maturity (L-50), the timing of spawning and the batch fecundity (n = 51). The size at maturity (L-50) for females was estimated to be 39.9 cm. The mean relative batch fecundity was 140 +/- 64 eggs g(-1) of fish. Spawning occurs during the monsoons and inter-monsoon seasons with peaks in the reproductive activity during the North-east and South-west monsoon events. Demographic differences were detected in the reproductive timing of the population and a large investment in gamete production was observed in fish with high hepatic condition and in their first spawning year.
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Numéro d'Appel LL @ pixluser @ collection 360
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Auteur Braham, C.B.; Freon, P.; Laurec, A.; Demarcq, H.; Bez, N.
Titre New insights in the spatial dynamics of sardinella stocks off Mauritania (North-West Africa) based on logbook data analysis Type Article scientifique
Année 2014 Publication Revue Abrégée (up) Fisheries Research
Volume 154 Numéro Pages 195-204
Mots-Clés
Résumé Sardinella spp. are the main species fished in Mauritanian waters. Logbook data (1991&8211;2009) were used to standardise CPUE. This clearly revealed that the abundance of sardinella peaked in the warm season (July&8211;September) which is the main, if not the only significant spawning season for round sardinella.

This study does not directly confirm or falsify the common belief that the adults migrate from the Senegalese EEZ up to north of the 21° N latitude, but it presents a variety of new hypotheses. If a single transboundary stock exists, part of its individuals, or a sub-stock, is probably more sedentary and remains in the permanent upwelling area located in northern Mauritania and southern Morocco.

Between years, changes in abundance index are dominated by a decrease from 1996 to 2006, depending on the months taken into account, and especially whether or not the warm (spawning) season is considered. For a given month, the spatial distribution of sardinella shows limited differences between years. In the southernmost latitudes of the Mauritanian EEZ the seasonal pattern, which is dominated by high catch rates during the warm season, is much stronger after the year 2001, and then tended to increase year after year.

Changes in species distribution and abundance during the twenty-year study period are difficult to relate to environmental dynamics. However, an inversion of the upwelling trend was observed in 2001, matching a change in the seasonality of sardinella catches, although the causality between the two phenomena could not be established. The increase in the abundance index of sardinella in the last five years, particularly during most of the core fishing season (July&8211;September) might be due to favourable oceanographic conditions (higher upwelling index) and/or changes in the fishing strategies or efficiency. Before annual indices of abundance can be used in the future, it will be necessary to better understand possible changes in catchability during the warm/spawning season.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1147
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Auteur Coll, M.; Carreras, M.; Cornax, M.J.; Massuti, E.; Morote, E.; Pastor, X.; Quetglas, A.; SàeZ, R.; Sobrino, I.; Torres, M.A.; Tudela, S.; Harper, S.; Zeller, H.; Pauly, D.
Titre Closer to reality : reconstructing total removals in mixed fisheries from Southern Europe Type Article scientifique
Année 2014 Publication Revue Abrégée (up) Fisheries Research
Volume 154 Numéro Pages 179-194
Mots-Clés
Résumé Underestimation of catches is especially important in countries where fishing fleets are highly diversified, the enforcement of fishery management is low, data availability is poor, and there is high demand for fish products in local markets. This is the case for southern European and Mediterranean regions. Adapting a catch-reconstruction approach, we estimated the total removals of marine resources by Spain for the Spanish Mediterranean Sea and Gulf of Cadiz regions from 1950 to 2010. We collected available information from scientific publications, the grey literature and secondary sources of information to complement officially reported catch data. We assessed missing catch sectors as time-point estimates, used as anchor points of reliable data upon which we then estimated total catch using interpolation to fill in the periods for which quantitative data were missing. Unreported removals and discards represented important portions of total removals in the study area. They accounted for, on average, 43% of total removals between 1950s and 2010, and were composed of black market sales, subsistence fishing, artisanal fishing, recreational fishing and illegal catch, in addition to discarding. By the late 2000s, recreational fishing was the most important sector for unreported landings (similar to 36%), followed by black market sales (similar to 32%), subsistence fishing (similar to 17%), unreported artisanal fishing (similar to 12%) and illegal catch (similar to 2%). The overall catch trend differed from the official trend highlighting that the depletion of marine resources in the region started earlier than previously observed. The catch composition changed with time, with a higher diversification of species in fish markets with time. These results indicate an earlier trend towards expansion of fisheries and depletion of marine resources.
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Editeur Lieu de Publication Éditeur
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Numéro d'Appel LL @ pixluser @ collection 381
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