Can a square-mesh panel inserted in front of the cod end improve size and species selectivity in Mediterranean trawl fisheries?

Brčić, Jure; Herrmann, Bent; Sala, Antonello

doi:10.1139/cjfas-2017-0123

Cited by 28 publications

(15 citation statements)

References 39 publications

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“…Earlier studies by Alzorriz et al (2016) and Brčić et al (2016Brčić et al ( , 2018, which were carried out in the Atlantic Ocean and the Mediterranean Sea, respectively, showed that few individuals of hake escaped through SMPs located in front of the codend and on the top panel of the trawl. These low escape rates were attributed mainly to the low contact probability between the fish and the SMP, which resulted in few fish being sizeselected by the panel.…”

Section: Discussionmentioning

confidence: 97%

“…On the other hand, SMPs can be an alternative measure to increase the escape of some species without excessively affecting profitability (Brčić et al 2016). Several studies have investigated the functioning and release efficiency potential of SMPs, but the release efficiency of SMPs has often been estimated to be low due to the low probability of contact of the fish with the panel (Herrmann et al 2014, Alzorriz et al 2016, Brčić et al 2018. There have been attempts to improve the fishpanel contact probability by inserting stimulating devices in the gear.…”

Section: Introductionmentioning

confidence: 99%

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Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery

et al. 2020

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Reduction of discards from the Basque mixed bottom trawl fishery is a challenge. To improve the selective properties of the gear used by the fleet and supplement codend size selection, a square mesh panel (SMP) installed in the upper panel of the trawl was introduced in 2006. However, recent studies have shown that the release efficiency of this SMP is low due to lack of contact between the fish and the SMP. In this study, we tested the release efficiency of the SMP for four different gear configurations. We tested the effect of adding LED lights at two different positions and altering panel size and panel position in the trawl. The analyses were focused on two species: hake (Merluccius merluccius) and blue whiting (Micromesistius poutassou). The results showed that the position of LED lights did not significantly affect the SMP's release efficiency for any species. However, increasing panel size had a significant positive effect on the release efficiency of blue whiting, and placing the SMP in the lower panel improved the release efficiency of hake. These results highlight the challenge of simultaneously improving the selective properties of gear for species with different behaviour, especially in mixed demersal fisheries. Eficiencia de escape y selectividad de cuatro configuraciones diferentes aplicadas a un panel de malla cuadrada en la pesquería multiespecífica de arrastre del País VascoResumen: La reducción de descartes en la pesquería de arrastre del País Vasco supone un problema importante. En 2006, se introdujo en la reglamentación la posibilidad de usar un Panel de Malla Cuadrada (SMP) en la zona anterior al copo para mejorar la selectividad de la red. Sin embargo, estudios recientes manifiestan que la eficiencia de escape de los peces es baja debido a la falta de contacto selectivo entre el pez y el panel. En este estudio, analizamos la eficiencia de diferentes configuraciones del SMP. Se analizó el efecto de luces LED colocadas en distintas posiciones, el efecto del tamaño del SMP y su localización. Estudiamos la merluza (Merluccius merluccius) y la bacaladilla (Micromesistius poutassou). La posición de las LED demostró no tener ningún efecto significativo sobre la eficiencia de escape del SMP para ninguna de las dos especies. Sin embargo, aumentar el área del panel tuvo un efecto significativo en la eficiencia de escape de la bacaladilla, mientras que el cambio de posición del SMP incrementó la eficiencia de escape de la merluza a través del SMP. Estos resultados muestran el reto que supone mejorar la selectividad de un arte de pesca simultáneamente para especies demersales con comportamientos diferentes.Palabras clave: panel de malla cuadrada; luces LED; pesca de arrastre; eficiencia de escape; merluza; bacaladilla. Citation/Como citar este artículo: Cuende E., Arregi L., Herrmann B., Sistiaga M., Basterretxea M. 2020. Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery. Sci. Mar. 84(1): 39-47. https://doi.org/10.3989/scimar.0...

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery

et al. 2020

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“…1967. However, a recent study (Brčić et al, 2018) has predicted a high risk of retention of undersized individuals of several species with both mesh types, highlighting the need for additional measures, besides codend size selection, to improve the exploitation pattern of Mediterranean bottom trawls. Square-Mesh Panels (SMPs) are among the simplest technological measures that can be applied to bottom trawls when codend size selection alone does not prevent retention of undersized individuals.…”

Section: Introductionmentioning

confidence: 99%

Effect of a lateral square-mesh panel on the catch pattern and catch efficiency in a Mediterranean bottom trawl fishery

et al. 2020

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The current legal codends used in Mediterranean bottom trawl fisheries are at high risk of retaining undersized individuals of several commercial fish species. This entails that codends alone are unable to provide the desired exploitation pattern. A simple technological measure that potentially can provide higher release efficiency of undersized fish are Square-Mesh Panels (SMPs). SMPs are often applied in the upper section of the trawl belly, just ahead the codend. However, recent studies in the Mediterranean have demonstrated that SMPs mounted in this position provided limited release efficiency, because very few fish came into contact with their meshes. In attempt to improve SMPs efficiency in the Mediterranean bottom trawl fisheries, we applied them on the lateral sides of the last tapered section of the trawl belly, just ahead of the codend, and fitted two guiding panels in the trawl belly to enhance fish-SMP contact. We compared the catch performance of a standard commercial trawl with a 52 mm diamond-mesh codend and of a similar trawl fitted with lateral SMPs (70 mm mesh size) in the belly using a twin trawl. The study focused on red mullet (Mullus barbatus), a commercially important species, but data for gurnard (Chelidonichthys lucerna and Chelidonichthys cuculus) were also obtained and analysed. In contrast to previous research on SMPs mounted in the top panel of the trawl, in this study SMPs induced a significant effect on catch performance for red mullet, demonstrating that their lateral position involved greater fish-SMP contact. However, since the test trawl lost a significant amount of legal-sized red mullet compared with the standard trawl, the effect was not wholly positive, possibly due to an excessively large mesh size. Therefore, future studies should be encouraged to test lateral SMPs with smaller mesh sizes.

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“…The size selectivity data was analyzed using the software SELNET (Herrmann et al 2012;Brčić et al 2018aBrčić et al , 2018b. We assumed that the probability of each redfish being retained after entering the codend was independent of other fish and that the number of individuals of a specific length class remaining in the codend or the cover has a binominal distribution (i.e., length-dependent retention probability).…”

Section: Selectivity Data Analysismentioning

confidence: 99%

Out with the old and in with the new: T90 codends improve size selectivity in the Canadian redfish (Sebastes mentella) trawl fishery

Cheng

Winger

Bayse

et al. 2020

Can. J. Fish. Aquat. Sci.

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The size selectivity of four codends were compared in the Gulf of St. Lawrence, Canada redfish fishery, including the regulated diamond mesh codend with a mesh opening of 90 mm (T0) and three experimental codends of different mesh openings (90, 100, 110 mm) in which the netting is turned 90° to the direction of tow (T90). Results for the regulated codend showed that there was little size selection, catching greater than 97% of redfish over all of the length classes observed. Considering the fished population, the smallest T90 codend would catch 30% fewer redfish under the Minimum Landing Size (MLS) of 22 cm compared with the T0 codend, but would also lose 16% of catch above 22 cm. The T90 codend with 100 mm mesh opening had the same size selectivity as the smallest T90 codend. The 110 mm T90 codend would catch 50% less redfish below MLS but lose 40% of redfish above. Overall, results show that T90 codends improve size selectivity in which large proportions of undersized fish are successfully released.

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Can a square-mesh panel inserted in front of the cod end improve size and species selectivity in Mediterranean trawl fisheries?

Cited by 28 publications

References 39 publications

Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery

Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery

Effect of a lateral square-mesh panel on the catch pattern and catch efficiency in a Mediterranean bottom trawl fishery

Out with the old and in with the new: T90 codends improve size selectivity in the Canadian redfish (Sebastes mentella) trawl fishery

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