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| Khaled, Ramez; Priour, Daniel; Billard, Jean-yves. |
| A numerical method for optimization of the cable lengths in trawls with respect to the ratio between the estimated trawl drag and the predicted catch efficiency is developed and applied. The trawl cables of interest are warps, bridles, headline and footrope. The optimization algorithm applies an ordered sequential process changing one cable length at the time. It is assumed in the predictions that the catch efficiency of the trawl is proportional with the trawl mouth area. In a case study optimizing a bottom trawl used on a research vessel by applying the new method it is predicted that it would be possible to reduce the ratio between trawl drag and catch efficiency by up to 46% by optimizing the cable lengths. Thus this would enable a considerable... |
| Tipo: Text |
Palavras-chave: Bottom trawl; Modeling; Optimization; Fuel consumption; Drag; Swept area; Mouth surface; Fish distribution. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00130/24106/22857.pdf |
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| Bez, Nicolas; Reid, David; Neville, Suzanna; Verin, Yves; Hjellvik, Vidar; Gerritsen, Hans D.. |
| Acoustic data are often collected during bottom trawl surveys. Their use can potentially improve the precision and accuracy of fish abundance estimates if acoustic data collected between trawl stations are consistent with those collected during trawling operations. This question is addressed here through the analysis of 20 bottom trawl surveys (three survey areas and five different survey series) with coincident acoustic measurements during and between trawl stations. Firstly, on-station and underway acoustic data were compared using statistics computed globally over each survey (average vertical profiles, global indices of collocations, and spatial structures) for various combinations of depth layers. Secondly, we focussed on underway acoustic data... |
| Tipo: Text |
Palavras-chave: Gear perturbation; Acoustic; Bottom trawl. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2486.pdf |
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| Merillet, Laurene; Mouchet, Maud; Robert, Marianne; Salaun, Michele; Schuck, Lucie; Vaz, Sandrine; Kopp, Dorothee. |
| Trawling activities are considered to be one of the main sources of disturbance to the seabed worldwide. We aimed to disentangle the dominance of environmental variations and trawling intensity in order to explain the distribution of diversity patterns over 152 sampling sites in the French trawl fishing-ground, the Grande Vasière. Using a towed underwater video device, we identified 39 taxa to the finest taxonomic level possible, which were clustered according to their vulnerability to trawling disturbance based on functional traits. Using generalized linear models, we investigated whether the density distribution of each vulnerability group was sensitive to trawling intensity and habitat characteristics. Our analyses revealed a structuring effect of depth... |
| Tipo: Text |
Palavras-chave: Bay of Biscay; Biodiversity; Bottom trawl; Fishing; Underwater video; Vulnerability. |
| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00406/51741/52436.pdf |
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| Mehault, Sonia; Morandeau, Fabien; Kopp, Dorothee. |
| The new Common Fisheries Policy may exempt some species from the landing obligation if a high survival rate can be demonstrated among discards. This study focuses on the survival capacity of Nephrops norvegicus discarded from trawlers of the Bay of Biscay (France). Three sea trials were conducted on board 3 commercial trawlers and 15 fishing operations were sampled. The vitality of Nephrops was classed into three categories (healthy, moribund or dead) before release at sea and samples of healthy and moribund individuals were kept in captivity on Nephrops grounds for three days. A Generalised Linear Model was used to examine the variability in the proportion of healthy Nephrops discarded, which was significantly influenced by tow duration, duration of air... |
| Tipo: Text |
Palavras-chave: Vitality; Captivity; South western waters; Bottom trawl; GLM. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00346/45695/45355.pdf |
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| Leonardi, Sophie; Rubin, Alex; Meillat, Marc; Coppin, Franck; Delpech, Jean-paul; Morandeau, Fabien; Larnaud, Pascal. |
| Ce rapport fait la synthèse des travaux réalisés en 2008 et en 2009 au cours du programme Selecmer. Celui-ci, réalisé à l'initiative des professionnels de la pêche en partenariat avec l'Ifremer, avait pour objectif de travailler à améliorer la sélectivité du chalut de fond qu'ils utilisent afin de diminuer les rejets des individus hors-tailles1, en particulier pour le merlan, tout en limitant les pertes commerciales immédiates. Une première phase a consisté à tester l'efficacité de fenêtres à mailles carrées. La deuxième phase a eu pour objectif de développer une grille sélective. Des essais en bassin et des campagnes vidéo en mer ont permis d'apporter des ajustements aux dispositifs sélectifs. L'ensemble des essais de sélectivité à bord des navires de... |
| Tipo: Text |
Palavras-chave: Professional fishermen; Square mehs; Flume tank; Selective grid; North Sea; Channel; Bottom trawl; Selectivity; Fishing; Professionnels; Mailles carrées; Campagnes à la mer; Bassin d'essais; Grille sélective; Mer du Nord; Manche; Chalut de fond; Sélectivité; Pêche. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/rapport-6776.pdf |
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