A year-long trial of a square mesh panel in a commercial demersal trawl

Bullough, L.W.; Napier, Ian; Laurenson, Chevonne H.; Riley, D. N.; Fryer, R. J.; Ferro, Richard; Kynoch, R.J.

doi:10.1016/j.fishres.2006.09.008

Cited by 20 publications

(11 citation statements)

References 12 publications

(14 reference statements)

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“…Earlier experiments with devices installed in the extension piece showed that the efficiency of the device depends largely on how close the device is to a catch accumu- Pagination not final (cite DOI) / Pagination provisoire (citer le DOI) lation zone such as the cod end (Bullough et al 2007;Herrmann et al 2014). Thus, devices that do not form, or have, an obstacle (i.e., lifting panel, guiding panel, sorting grid, etc.)…”

Section: Discussionmentioning

confidence: 99%

Improving release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery by stimulating escape behaviour

Grimaldo

Sistiaga

Herrmann

et al. 2018

Can. J. Fish. Aquat. Sci.

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Abstract:We tested the ability of stimulators to improve the release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) through the meshes of a square mesh section installed in a trawl. The section was tested in three different configurations: without any stimulation device, with a mechanical stimulation device, and with LED light stimulation devices. We analysed and compared the behaviour of cod and haddock in all three configurations based on release results and underwater recordings. Parallel to the fishing trials, we carried out fall-through tests to determine the upper physical size limits for cod and haddock to be able to escape through the square meshes in the section. This enabled us to infer whether lack of release efficiency was due to fish behaviour or release potential of the square meshes in the section. The results showed that the escape behaviour of haddock can be triggered by mechanical stimulation. In contrast, cod did not react significantly to the presence of mechanical stimulators. LED light stimulation had some effect on the behaviour of haddock, but not on cod.Résumé : Nous avons vérifié la capacité de stimulateurs d'améliorer l'efficacité de la libération de morues (Gadus morhua) et d'aiglefins (Melanogrammus aeglefinus) par les mailles d'une section de mailles carrées installée dans un chalut. La section a été mise à l'essai selon trois configurations différentes, soit sans aucun instrument de stimulation, avec un instrument de stimulation mécanique et avec des instruments de stimulation à lumière DEL. Nous avons analysé et comparé le comportement des morues et des aiglefins dans les trois configurations à la lumière des résultats de libération et d'enregistrements sous l'eau. Parallèlement aux essais de pêche, nous avons mené des essais de passage par gravité afin de déterminer les limites supérieures des tailles auxquelles les morues et aiglefins peuvent s'évader par les mailles carrées dans la section. Cela nous a permis d'établir si l'absence d'une libération efficace était due au comportement des poissons ou au potentiel de libération des mailles carrées dans la section. Les résultats montrent que le comportement d'évasion des aiglefins peut être déclenché par une stimulation mécanique. Les morues, au contraire, n'ont pas présenté de réaction significative à la présence de stimulateurs mécaniques. La stimulation à la lumière DEL a eu un certain effet sur le comportement des aiglefins, mais pas sur celui des morues. [Traduit par la Rédaction]

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Section: Discussionmentioning

confidence: 99%

Improving release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery by stimulating escape behaviour

Grimaldo

Sistiaga

Herrmann

et al. 2018

Can. J. Fish. Aquat. Sci.

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“…However, recent field experiments showed no significant effect of using square codend or square mesh panel on the selectivity of trawl codends (Bullough et al, 2006;He, 2006). The same conclusion has been shown by Erickson et al (1996), who found that no significant effect for the square mesh panel on the escapement of undersize walleye pollock as the catch size increases, and they recommended the use of sorting grids to permit escapement of undersized fish before they reach the codend of pelagic trawls, without restricting the catch limits.…”

Section: Discussionmentioning

confidence: 97%

Behaviour analysis of undersized fish escaping through square meshes and separating grids in simulated trawling experiment

et al. 2007

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Abstract:Understanding fish escaping behavior through any given bycatch reduction device represents the cornerstone for its application as a technical conservation measure. To evaluate the square meshes and sorting grids as successful size-selective bycatch reduction devices in finfish trawl nets, we carried out a simulated trawling experiment to assess the effects of illumination, towing speed, and mesh or grid orientation on undersize fish escaping behavior through the square meshes and rigid grids. Juveniles masou salmon of an average body length of 130 mm were used as the experimental fish. A speed-controllable motor was used to tow the framed net in a circular water tank. Infrared CCD Camera fixed to the towed net, through a rotary connector, was used to observe fish behavior. Results demonstrated that, in contrast to the active escaping under light conditions, there was no active voluntary escaping under dark conditions. As a result, no fish could escape through the parallel and the sloping backward meshes and only 13 % passively escaped through the sloping forward meshes by increasing the towing speed. On the other hand, the probability of encounter and passive fish escaping through the longer openings between the sloping backward grids increased under dark conditions resulting in the highest escaping ratio that more increased from 67 % to 87 % by increasing the towing speed from 1 to 1.5 knot, and also shortened the swimming time before escaping from 5 to 1.5 minutes (the highest escaping ratio and the shortest swimming time before escaping under dark). Frame by frame analysis of some escaping events demonstrated an easy and passive fish escape through the grids without changing the normal swimming direction. Results support the use of the sloping backward grids (at the top panels as in the "Sort-V" grid system or at the bottom panels as in the form of "Evaflex" grid system 2 of a convenient grid material, area and slot size) as a size-selective bycatch reduction device well ahead of the codend of finfish trawl, especially demersal, working under dark at high towing speeds.

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“…Del mismo modo, Graham & Kynoch (2001) señalan que en paneles de escape la probabilidad de escape sería menor dada la dependencia que existe entre la proximidad del pez con el panel y el enmascaramiento visual al interior del copo. Aun cuando se reconoce este efecto, no hay duda que los paneles de malla cuadrada instalados adecuadamente en las redes de arrastre pueden reducir significativamente las capturas bajo talla (Madsen et al, 2002;Bullough et al, 2007). Esta bien establecido que en los artes de arrastre, la selección de los peces ocurre típicamente en el túnel y copo de la red, y es mayoritariamente una función de la relación entre su morfología y la disponibilidad de abertura de las mallas (Wileman et al, 1996).…”

Section: Discussionunclassified

Efecto del uso de paneles de escape de malla cuadrada sobre la reducción de peces juveniles en la pesquería de arrastre de merluza común (Merluccius gayi gayi)

Queirolo

Melo

Hurtado

et al. 2008

Lat. Am. J. Aquat. Res.

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RESUMEN. La evaluación de paneles de escape de malla cuadrada en redes de arrastre de fondo usadas en la pesquería de merluza común se realizó empleando dos metodologías complementarias: lances con sobrecopo y lances alternados. Los lances con sobrecopo permitieron cuantificar la fracción de la captura que escapa a través de los paneles de escape, y determinar la estructura de tallas y pesos medios, estimando longitudes de retención y rangos de selección. Se determinó la fracción bajo 30 y 36 cm de longitud total presentes en el copo y en el sobrecopo, ambos como indicadores del efecto selectivo que éstas producen. Los lances alternados permitieron verificar la disminución de los rendimientos de captura, tanto en número como en peso, aumentando los pesos medios de los ejemplares retenidos y disminuyendo la proporción de ejemplares bajo tallas de referencia, lo que indica la existencia de un efecto de escape en la fracción juvenil del stock.Palabras clave: paneles de escape, malla cuadrada, redes de arrastre de fondo, Merluccius gayi gayi, selectividad, peces juveniles, Chile.Effect of the use of square mesh escape panels on the reduction of young fish in the common hake (Merluccius gayi gayi) trawl fishery ABSTRACT. The evaluation of square mesh escape panels in bottom trawl nets used in the common hake fishery was carried out employing two complementary methodologies: top cover and alternated hauls. The top cover hauls were used to quantify the fraction of the catch that escapes through the panels and to determine the size structure and mean weight of the catch, estimating the retention sizes and selection ranges. The fractions under 30 and 36 cm of total length present in the codend and in the top cover were determined as proxies for the selective effect produced by the escape panels. The alternated hauls were used to verify the decrease in the catch rate, both in number and in weight, increasing the mean weight of the retained catch and decreasing the proportion under the reference length, for which we concluded that an escape effect does occur on the young fraction of the stock.

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A year-long trial of a square mesh panel in a commercial demersal trawl

Cited by 20 publications

References 12 publications

Improving release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery by stimulating escape behaviour

Improving release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery by stimulating escape behaviour

Behaviour analysis of undersized fish escaping through square meshes and separating grids in simulated trawling experiment

Efecto del uso de paneles de escape de malla cuadrada sobre la reducción de peces juveniles en la pesquería de arrastre de merluza común (Merluccius gayi gayi)

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