Selectivity experiments in the NE Mediterranean: the effect of trawl codend mesh size on species diversity and discards

Stergiou, K.Ι.

doi:10.1006/jmsc.1997.0231

Cited by 53 publications

(42 citation statements)

References 6 publications

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“…Moreover, several bottom trawl selectivity studies have demonstrated that high discard rates, with a large proportion of immature small size specimens and non-commercial invertebrates, is a general problem of the trawl fishery in the Mediterranean Sea (e.g. Stergiou et al 1997, 1998, Vassiloupou and Papaconstantinou 1998, Sánchez et al 2004, Ordines et al 2006. These studies showed that replacing the 40-mm diamond mesh with the 40-mm square mesh in the codend improves the selectivity of bottom trawling while maintaining commercial yields for most of the species.…”

Section: Discussionmentioning

confidence: 99%

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Keskin¹,

Ordines²,

Ateş³

et al. 2014

Sci. Mar.

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Summary: This short-term study on commercial discards was carried out in fishing grounds around Gökçeada Island in the northeastern Aegean Sea, a geographic area where fisheries information is rather limited. A total of 28 bottom trawls were performed between 70 and 410 m depth from December 2009 to February 2010. All the samples were collected on board a commercial trawler under commercial fishing conditions. A total of 3143 kg of biomass was caught in 28 valid hauls. Landings accounted for about 67% of the total catch while the remaining 33% was discarded. Fish species comprised 85% of the total catch and their composition could be divided into four main groups related to depth: shallow shelf (70 to 88 m), deep shelf (155 to 180 m), shelf break (196 to 276 m), and upper slope (307 to 410 m). Fish dominated the abundance and biomass of both landings and discards in all bathymetric strata. Echinoderms also accounted for a large proportion of the discards. Mean total catches varied between 78.4 kg/h on the shallow shelf and 38.1 kg/h on the shelf break with no differences in the landing biomass between groups, but with slightly higher discards over the shallow shelf. Taking into account the preliminary nature of the findings, based on a short-term analysis, the minimum mesh size and minimum landing size currently applied in the Turkish bottom trawl fishery are not sufficient to reduce discards and to protect juveniles of commercially important species in the northeastern Aegean Sea.Keywords: bottom trawl; catch composition; landings; discards; length-frequency; eastern Mediterranean. Evaluación preliminar de los desembarques y descartes de la pesquería de arrastre de fondo de Turquía en el mar Egeo nororiental (Mediterráneo oriental)Resumen: Este estudio a corto plazo sobre los descartes de la flota comercial de arrastre se llevó a cabo en las zonas de pesca alrededor de la isla Gökçeada en el noreste del mar Egeo, una zona geográfica en la que la información sobre las pesquerías es bastante limitada. Se realizaron un total de 28 pescas de arrastre de fondo entre 70 y 410 m de profundidad de diciembre 2009 a febrero de 2010. Todas las muestras se recogieron a bordo de un embarcación de pesca de arrastre siguiendo las mismas condiciones de pesca comercial. Se capturaron un total de 3143 kg de biomasa en 28 lances válidos. Los desembarques comerciales representaron alrededor del 67% de la captura total, mientras que el resto (33%) se descartó. El 85% de la captura total estuvo compuesta por especies de peces. La composición específica se pudo separar en cuatro grupos principales relacionados con la profundidad : la plataforma poco profunda (70 a 88 m), la plataforma profunda (155-180 m), el borde inferior de la plataforma (196 a 276 m) y el talud superior (307-410 m). Los peces dominaron la abundancia y biomasa tanto de los desembarques comerciales como de los descartes en todos los estratos batimétricos. Además los equinodermos también fueron un grupo importante de los descartes. La media de las capturas totales v...

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Section: Discussionmentioning

confidence: 99%

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Keskin¹,

Ordines²,

Ateş³

et al. 2014

Sci. Mar.

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“…The most widely acknowledged ones rely on the biological impact of selectivity measures. Selectivity has positive consequences on non-commercial species and on the biomass and age-structure of commercial stocks (Beverton and holt 1957;Kvamme and Fröysa 2004;Maclennan 1995;Salini et al 2000;Stergiou et al 1997;Suuronen and Sardà 2007;VanMarlen 2000;Ward 1994) 1 . Another important social benefit is due to the fact that rights-based systems of fisheries management are easier to implement when fishing is selective; i.e., when unsought joint productions are minimized.…”

Section: Introductionmentioning

confidence: 99%

Optimal Selectivity and Effort Cost A Simple Bioeconomic Model with an Application to the Bay of Biscay Nephrops Fishery

Macher

Boncœur²

2010

Marine Resource Economics

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“…An indication of this is the high share of juvenile fish in the catches (Larrañeta et al, 1969;Stergiou et al, 1997;Lleonart, 2001;Sánchez et al, 2004). Poor selectivity of bottom trawls using the legislated 40-mm diamond mesh codend greatly contributes to the unfavourable catch composition and relatively high discard rates (Martín et al, 2001;Sánchez et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

The use of a square mesh codend and sorting grids to reduce catches of young fish and improve sustainability in a multispecies bottom trawl fishery in the MediterraneanEl uso de copo de malla cuadrada y rejillas separadas para reducir las capturas de pece

Sardà¹,

Bahamón²,

Molı́³

et al. 2006

Sci. Mar.

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SUMMARY: In order to improve the capacity of bottom trawl fishing gears to reduce catches of young fish and discards in a highly exploited demersal trawl fisheries in the Mediterranean, the size-selection performance of a 36-mm square-mesh codend and two sorting grids with 20 and 15 mm bar spacing was assessed. Alternate hauls were used to assess the selectivity of 36-mm square-mesh codend. Selectivity of sorting grids was assessed using a double codend in which fish that escaped through the grid were captured in the lower codend while other fish were guided into the upper codend. The mean selection length (L 50 ) for European hake was 18.5 cm and that for the Atlantic horse mackerel was 14.0 cm with the 36-mm square-mesh codend . These values are close to their current minimum landing sizes (20 cm for hake and 12 cm for horse mackerel). The sorting grid with 20-mm bar spacing showed L 50 value of 13.3 cm for hake, suggesting that a larger grid-spacing would be needed to obtain sufficient sorting performance. Similarly, for Atlantic mackerel the estimated L 50 of 14.3 cm indicates that larger grid spacing is required to attain an L 50 that would be close to the current MLS (18 cm). For Atlantic horse mackerel and red mullet, the L 50 obtained with the sorting grid with 20-mm bar spacing was close to the MLS of these species (the MLS of red mullet is 11 cm). The selectivity of the sorting grid with 15-mm bar spacing was generally very poor. Size-selection performance of sorting grids was assessed for the first time in the local fisheries. In order to effectively improve size-selection, seasonal and depth-dependent differences between target and by-catch species must be taken into account, which is a good indicator of the difficulty of implementing a single mesh size or grid spacing in the Mediterranean demersal trawl fishery.Keywords: Mediterranean Sea, sorting grid, square mesh, selectivity, multispecies fishery, bottom trawl, European hake, Atlantic horse mackerel, Atlantic mackerel, red mullet. RESUMEN: EL USO DE COPO DE MALLA CUADRADA Y REJILLAS SEPARADORAS PARA REDUCIR LAS CAPTURAS DE PECES JUVENILES Y MEJORAR LA SOSTENIBILIDAD DE UNA PESQUERÍA MULTIESPECÍFICA DE ARRASTRE DE FONDO EN ELMEDITERRÁNEO. -Con el propó-sito de mejorar la capacidad de las redes de arrastre de fondo para reducir las capturas de peces juveniles y descartes en una pesquería multiespecífica altamente explotada en el Mar Mediterráneo, se evaluó la selectividad de las tallas de diversas especies demersales mediante el uso de una malla cuadrada de 36 mm y dos rejillas con separación entre barras de 20 y 15 mm. Se usó el método de lances alternativos para evaluar la selectividad del copo de malla cuadrada. La selectividad de las rejillas se evaluó mediante un doble copo. Los peces que escaparon de la rejilla se capturaron en el copo inferior y el resto del pescado se guió y capturó en el copo superior. Con el copo de malla cuadrada, la talla media de madurez (L 50 ) de la merluza y el jurel fue respectivamente de 18,5 cm y 14,0 cm. Estos v...

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Selectivity experiments in the NE Mediterranean: the effect of trawl codend mesh size on species diversity and discards

Cited by 53 publications

References 6 publications

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Preliminary evaluation of landings and discards of the Turkish bottom trawl fishery in the northeastern Aegean Sea (eastern Mediterranean)

Optimal Selectivity and Effort Cost A Simple Bioeconomic Model with an Application to the Bay of Biscay Nephrops Fishery

The use of a square mesh codend and sorting grids to reduce catches of young fish and improve sustainability in a multispecies bottom trawl fishery in the MediterraneanEl uso de copo de malla cuadrada y rejillas separadas para reducir las capturas de pece

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