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| Registros recuperados: 64 | |
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| Lehodey, Patrick; Marchal, Paul; Grandperrin, René. |
| Commercial and scientific bottom longline catches of alfonsino, #Beryx splendens$, from seamounts of New Caledonia were sampled to study length-frequency distributions. A total of 14,674 fish were measured. CPUE of #Beryx splendens$ on two seamounts is modelled in terms of length and depth. The data show that mean length increases with depth ; this is well described by a bivariate normal model that estimates catch for a given seamount. In addition, the data show that mean length also varies with the depth of the top of seamounts ; this is described by a recursive model that is designed to predict approximate catch for any seamount. The limitations of both models are discussed, particularly with regard to temporal variation. (Résumé d'auteur) |
| Tipo: Text |
Palavras-chave: POISSON MARIN; ECHANTILLONNAGE; LONGUE LIGNE; CROISSANCE; PROFONDEUR; ANALYSE STATISTIQUE; MODELE MATHEMATIQUE. |
| Ano: 1994 |
URL: http://www.documentation.ird.fr/hor/fdi:010006413 |
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| Marchal, Paul; Ulrich, Clara; Pastoors, M. |
| The scope of this study is to investigate the extent to which area-based management may have influenced the fishing efficiency of the Danish and Dutch demersal fleets harvesting cod, plaice and sole in the North Sea. Special consideration is given to the 'plaice box', a restricted area where fishing is prohibited to towed-gear fleets of horsepower exceeding 300 hp. An index of fishing power is calculated as the log-ratio between the catch per unit effort (CPUE) of any vessel and some survey abundance index. Annual trends in fishing are calculated as the year-effect derived from a general linear model (GLM) analysis of the index of fishing power. The fishing efficiency of Danish gill-netters and, to some extent, Danish seiners, has overall increased inside... |
| Tipo: Text |
Palavras-chave: Fishing efficiency; Plaice box; Fisheries management; North Sea; Demersal fisheries. |
| Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/00589/70118/68112.pdf |
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| Holley, Jean-francois; Marchal, Paul. |
| A typology is presented for the French offshore fleet fishing in the North Atlantic. The investigation was carried out separately for all years between 1985 and 2002. Two methods were combined: PCA and cluster analysis. In 1985, most vessels targeted saithe off western Scotland (vessels from Lorient) and in the northern North Sea (vessels from Boulogne and Fecamp). Then, probably because of the decline in biomass of saithe, some vessels started to target deepwater species from the early 1990s. In 2002, some vessels fished exclusively for saithe (>80%), while others targeted mainly deepwater species. In all, 12 fisheries are identified for the period 1985-2002. Results are given of a preliminary investigation trying to identify the external factors... |
| Tipo: Text |
Palavras-chave: Saithe; Multivariate analyses; Mixed fisheries; Fishing strategy; Fisheries dynamics; Deepwater species. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-384.pdf |
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| Marchal, Paul; Andersen, B; Bromley, D; Iriondo, A; Mahevas, Stephanie; Quirijns, F; Rackham, B; Santurtun, M; Tien, N; Ulrich, Clara. |
| The scope of this paper is to quantify, for a wide selection of European fisheries, fishing tactics and strategies and to evaluate the benefits of adjusting the definition of. fishing effort using these elements. Fishing tactics and strategies were identified by metiers choices and a series of indices. These indices have been derived to reflect shifts in tactics (within a fishing trip) and in strategies (within a year). The Shannon-Wiener spatial diversity indices of fishing tactics (FT_SW) and strategies (YE_SW) had the greatest impact on catch rates. In particular, FT_SW was always negatively correlated to catch rates. One may anticipate that during a fishing trip, vessels with high FT_SW have been searching fish aggregations for a long time, while... |
| Tipo: Text |
Palavras-chave: Fishing effort; Fishing mortality; Catch rates; GLM modeling; Skipper effect. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/2006/publication-1339.pdf |
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| Marchal, Paul; Andersen, Bo; Caillart, B.; Eigaard, Ole; Guyader, Olivier; Hovgaard, Holger; Iriondo, Ane; Le Fur, Fanny; Sacchi, Jacques; Santurtun, Marina. |
| Face-to-face interviews were conducted to identify the main changes in gear and vessel technology that may have improved the fishing efficiency of a number of French, Danish, and Basque fleets over the past few decades. Important changes include the gradual appearance of twin trawls (Danish and French trawlers) and trammel-nets (French gillnetters), and the increased polyvalence of Basque bottom trawlers. The results suggest that fishing effort descriptors that are not traditionally measured (gear type, groundrope type, length of net used per day, headline length, crew size, number of winch or net drums) may have a substantial impact on catch rates. Adjusting fishing effort using such descriptors may generally improve the relationship between fishing... |
| Tipo: Text |
Palavras-chave: Twin trawls; Technological creep; Groundrope; Generalized linear models; Fishing mortality; Fishing effort; Catch rate. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2611.pdf |
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| Marchal, Paul; Poos, Jan-jaap; Quirijns, Floor. |
| This study has investigated some properties of fishermen's foraging, using Levy flights theory. The case studies examined were a selection of North Sea Dutch and French vessels, for which catch and effort data were collected on a haul-by-haul basis. Foraging behavior could reasonably be represented by a Levy flight process, characterized by an exponentiation factor mu, for both fleets. The properties of fishers' foraging were further investigated for the Dutch fleet using time series analysis. Optimal foraging was found with mu = 1.5, suggesting a slow recovery dynamics of the stocks being harvested. Efficient foraging led to high value per unit effort, while the knowledge of fishing grounds with high stock density is shown to increase foraging efficiency... |
| Tipo: Text |
Palavras-chave: Haul by haul data; Foraging; Fishing effort; Levy flights; Fleet behavior. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2314.pdf |
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| Marchal, Paul. |
| A quantitative comparison between metiers and resulting catch profiles was carried out for seven French demersal and pelagic fleets operating in the North Sea, the eastern Channel, and the Bay of Biscay. Typologies for four metiers have been attempted, based on different factors (gear, mesh size, fishing ground, and/or a priori target species), data sources (logbooks or harbour enquiries), and aggregation levels. Catch profiles were selected through cluster analysis. The linkage between metiers and catch profiles was quantified using uncertainty coefficients, which depended on the metier typology being used and the fleet under consideration, but were not subject to substantial inter- or intra-annual fluctuations. Future catch profiles and metiers were... |
| Tipo: Text |
Palavras-chave: Uncertainty coefficients; Metiers; Fleets; Fishing intention; Catch profiles. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4075.pdf |
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| Vermard, Youen; Marchal, Paul; Mahevas, Stephanie; Thebaud, Olivier. |
| The scope of this paper is to describe, evaluate, and forecast fishing trip choices of the Bay of Biscay pelagic fleet using random utility modeling (RUM). First, alternative fishing trip choices of this fleet were identified using multivariate statistical methods based on species landings weighted by value and defined as distinct fishing activity or fisheries (termed metiers). A RUM was specified, which included trip components as attributes during the period 20012004 ( a lagged percentage of the value per unit of effort of the main species caught, total value per unit of effort, and inertia in terms of changes from one metier to another). For the main metiers, the proportion of correct effort allocation is 90% during the calibration period of 2001-2004.... |
| Tipo: Text |
Palavras-chave: Management; Métier; Fishing effort; Fisher's behavior; RUM. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6096.pdf |
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| Marchal, Paul; Francis, Chris; Lallemand, Philippe; Lehuta, Sigrid; Mahevas, Stephanie; Stokes, Kevin; Vermard, Youen. |
| Managing adequately the exploitation of commercial species subject to technical interactions is a key step towards the ecosystem approach to fisheries. We evaluate here, using a bio-economic modelling approach building on the ISIS-Fish simulation platform, the relative impact of total allowable commercial catches (TACC) and of taxes applicable to over-quota landings (deemed value) on the sustainability of a selection of species exploited by the New Zealand hoki (Macruronus novaezelandiae) fishery. We investigate some aspects of the hoki mixed fisheries, consisting of four fleets and nineteen metiers, by considering the technical interactions between hoki and Southern hake (Merluccius australis). The dynamics of effort allocation were modelled using gravity... |
| Tipo: Text |
Palavras-chave: Fleet dynamics; New Zealand hoki fishery; Deemed value; Fisheries management. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00000/11168/7521.pdf |
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| Vermard, Youen; Rivot, Etienne; Mahevas, Stephanie; Marchal, Paul; Gascuel, Didier. |
| Recent advances in technologies have lead to a vast influx of data on movements, based on discrete recorded position of animals or fishing boats, opening new horizons for future analyses. However, most of the potential interest of tracking data depends on the ability to develop suitable modelling strategies to analyze trajectories from discrete recorded positions. A serious modelling challenge is to infer the evolution of the true position and the associated spatio-temporal distribution of behavioural states using discrete, error-prone and incomplete observations. In this paper, a Bayesian Hierarchical Model (HBM) using Hidden Markov Process (HMP) is proposed as a template for analyzing fishing boats trajectories based on data available from... |
| Tipo: Text |
Palavras-chave: Bayesian Hierarchical Models; Hidden Markov Model; State-space model; VMS; Fleet behaviour; Fishing effort. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00009/11993/9342.pdf |
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| Marchal, Paul. |
| Ce mémoire présente une contribution à la recherche sur la dynamique de la mortalité par pêche (F) et son impact sur la gestion des ressources halieutiques. La première étape de cette démarche a été de réduire la complexité des systèmes halieutiques étudiés, en regroupant les bateaux et leurs activités en flottilles et métiers respectivement. Plusieurs méthodes existent pour définir les métiers, certaines basées sur les variables d’entrée (engin, zone de pêche, espèces cibles), d’autres sur les variables de sortie (profils de capture). Une comparaison de ces méthodes pour les flottilles françaises indique que les meilleures correspondances sont obtenues pour les flottilles les plus sélectives (e.g., chalutiers pélagiques, fileyeurs). Une fois les... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00031/14251/11535.pdf |
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| Registros recuperados: 64 | |
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