Predictive models and comparison of the selectivity of standard (T0) and turned mesh (T90) codends for three species in the Eastern Mediterranean

Tokaç, Adnan; Herrmann, Bent; Aydın, Celalettin; Kaykaç, Hakan; Ünlüler, Arcan; Gökçe, Gökhan

doi:10.1016/j.fishres.2013.10.015

Cited by 39 publications

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References 31 publications

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“…Previous studies from the Mediterranean have shown that increasing mesh size in the trawl codends improves the L50 values (Özbilgin et al, 2012;Tokaç et al, 2014). In this study, It was determined that increasing mesh size (from 44 to 50 mm) would lead to in the range of 7 to 17% increase in L50 values for three species except Atlantic horse mackerel.…”

Section: Discussionmentioning

confidence: 84%

“…Turned mesh (T90) gave higher L50 values than both D44 (despite 10% higher mesh size) and same mesh size of square mesh (S40) for red mullet and Atlantic horse mackerel. Similarly, Tokaç et al (2014) found that 40 mm mesh size T90 codend improves selectivity as 9% compared to 44 mm diamond mesh codend for red mullet.…”

Section: Discussionmentioning

confidence: 85%

“…Moreover, red mullet selectivity studies were mostly carried out 25-50 m depth ranged with experimental trawl and relatively short towing duration (Aydın et al, 2011;Tokaç et al, 2014). Only Ateş et al (2010) conducted on the commercial trawler between 36 and 207 m in the Mediterranean Sea.…”

Section: Introductionmentioning

confidence: 99%

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Dereli̇¹,

Aydın²

2016

Turk. J. Fish. Aquat. Sci.

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This paper compares the selectivity of 44 mm diamond mesh codend used in commercial fisheries (D44) and alternative codends 50 mm diamond (D50), a 40 mm square (S40) and a 40 mm 90° turned mesh (T40) for red mullet Mullus barbatus, European hake Merluccius merluccius, Morocco dentex Dentex maroccanus, Atlantic horse mackerel Trachurus trachurus in the Eastern Mediterranean demersal trawl fishery. Sea trials were carried out in the international waters between Turkey and Greece (Aegean Sea), with commercial trawler. Selectivity data were collected using the covered codend method and analysed by means of a logistic equation with the maximum likelihood method. Mean selection curves were estimated and compared using the between-haul variations model. The mean 50% retention total length values (L50) of D44, D50, S40 and T40 codends are 11.1, 12.9, 12.9 and 13.6 cm for red mullet, 12.3, 14.4 and 14.3 cm for hake, 10.0, 10.7, 10.3 and 8.4 cm for Morocco dentex and 16.2, 14.2, 15.3 and 17.1 cm for mackerel, respectively. The results show that there are statistically differences between L50 values of four codends for only red mullet. S40 and T40 codends improve the selectivity of red mullet when considering commercially D44 codend.Keywords: Codend selectivity, mesh shape, Eastern Mediterranean, demersal trawl. Doğu Akdeniz Dip Trol Balıkçılığında Dört Tür İçin Ticari ve Alternatif Torbaların Seçiciliği ÖzetBu çalışmada Doğu Akdeniz demersal trol balıkçılığında ticari olarak kullanılan 44 mm baklava gözlü torba (D44) ile 50 mm baklava gözlü (50D), 40 mm kare gözlü (S40) ve 40 mm 90° döndürülmüş (T40) alternatif torbaların barbunya Mullus barbatus, bakalyaro Merluccius merluccius, Fas mercanı Dentex maroccanus ve istavrit Trachurus trachurus için seçicilikleri karşılaştırılmıştır. Denemeler ticari trol teknesi ile Türkiye ile Yunanistan arasında kalan uluslararası sularda (Ege Denizi) yürütülmüştür. Seçicilik verisi çemberli örtü torba tekniği ile toplanmış ve lojistik eşitliğin maksimum olabilirlik yöntemi ile analiz edilmiştir. Ortalama seçicilik eğrileri, çekimler arası varyasyon modeli kullanılarak tahmin edilmiş ve karşılaştırılmıştır. D44, D50, S40 ve T40 torbalarındaki ortalama % 50 yakalama boyları (L50) barbunya için sırasıyla 11,1; 12,9; 12,9 ve 13,6 cm, bakalyaro için 12,3; 14,4 ve 14,3 cm, Fas mercanı için 10,0; 10,7; 10,3 ve 8,4 cm ve istavrit için 16,2; 14,2; 15,3 ve 17,1 cm olarak tespit edilmiştir. Bulgular, dört torbanın L50 değerleri arasında istatistiksel farkın sadece barbunya için bulunduğunu göstermektedir. S40 ve T40 torbalar, ticari olarak kullanılan D44 torbaya göre barbunyanın seçiciliğini geliştirmiştir.Anahtar Kelimeler: Torba seçiciliği, göz şekli, Doğu Akdeniz, demersal trol.

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Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 85%

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Dereli̇¹,

Aydın²

2016

Turk. J. Fish. Aquat. Sci.

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“…The results obtained indicated that the 40T90 t rawl codend was more selective co mpared to the 40D t rawl codend at red mullet selectiv ity. The use of trawl codends of the same net mesh size as T90 has been observed to have a positive effect on the selectivity of the red mu llet in both experimental studies (Kaykaç, 2005) and in the model experiments (Tokaç et al, 2014).…”

Section: Discussionmentioning

confidence: 96%

“…It is known that square mesh protects their openness under the physical load with respect to diamond mesh nets and therefore allows s mall individuals to escape (Wileman et al, 1996). It has been found that escapes are high when on the trawl codends are provided with mesh openings appropriate for the morphology of any species (Tosunoğlu, 2007;Tokaç et al, 2014;Tokaç et al, 2016). Although the square mesh trawl codend in favour of red mu llet selectivity gives positive results, it is known that it is not preferred by the fisherman due to the difficulty of construction and repair of the net (Graham, Kynoch, & Fyer, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Kaykaç¹,

Zengin²,

Tosunoğlu³

2018

Turk. J. Fish. Aquat. Sci.

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M ore than half of the landing (70%) of Red mullet (Mullus barbatus) in Turkey is provided from the Black Sea, which is almost all (96%) with bottom trawls. The effect of demersal trawl codend mesh shape and size on the s electivity of Red mullet in the Black Sea was investigated. Selectivity trials were conducted in August 2014 on a commercial trawl boat with conventional (40D), 36 and 40 mm square mesh (36S and 40S) and turned mesh codends (40T90). Data were collected using the covered codend method with a total of 21 valid hauls and selection parameters were obtained by fitting a logistic equation using maximum likelihood method. The L 50 value was found to be very low at 9.79 cm in the 40D trawl codend, while the L 50 value of 40S (11.89 cm) and 36S (10.59 cm) codends was obtained 21.5% and 8.2% better compared to the 40D, respectively. According to the traditional trawl codend, a L 50 value increase of 5.1% was observed in 40T90 (10.29 cm). Although all these values are below the M inimum Landing Size of the species, changes to the traditional mesh, especially in the shape of the mesh, can lead to significant improvements in size selectivity.

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Relative Catch Performance of Two Gear Modifications Used to Reduce Bycatch of Undersized Fish and Shrimp in Mediterranean Bottom Trawl Fisheries

et al. 2021

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The catch of large quantities of sublegal-sized fish and shrimp is a pervasive feature of bottom trawl fisheries, particularly in the Mediterranean demersal mixed fisheries where regulations traditionally allow small mesh sizes. To address these concerns, two bottom trawl net selectivity trials were carried out in 2019 and 2020 on fishing grounds worked by the trawl fleet of Spanish Mediterranean, under normal commercial operating conditions with volunteer trawlers of the local fleet. The traditional otter bottom trawl employed in the demersal mixed fishery was modified with a 50-mm T90 panel on the extension piece under two different configurations (front of the extension piece and back of the extension piece). A second modification consisted of inserting a selective grid in the extension piece of the standard bottom trawl net. The species investigated in the demersal mixed fishery were European Hake Merluccius merluccius, Red Mullet Mullus barbatus, Striped Red Mullet Mullus surmuletus, and the deepwater rose shrimp Parapenaeus longirostris. Important selectivity improvements were observed for European Hake and deepwater rose shrimp, particularly in the selective grid trial, where 95% and 100%, respectively, of undersize specimens escaped through the grid. The design with the T90 panel in the back of the extension piece allowed for a reduction of 35% of sublegal-sized individuals of European Hake, but no difference was gained in the sizes of both Mullus spp. retained in the cod end. The adoption of these gear modifications might contribute to reducing discards of sublegal-sized fractions of the fisheries target species.

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Predictive models and comparison of the selectivity of standard (T0) and turned mesh (T90) codends for three species in the Eastern Mediterranean

Cited by 39 publications

References 31 publications

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Relative Catch Performance of Two Gear Modifications Used to Reduce Bycatch of Undersized Fish and Shrimp in Mediterranean Bottom Trawl Fisheries

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