Selectivity of turned meshes codends for Deepwater Rose Shrimp (Parapenaeus longirostris), Horse Mackerel, (Trachurus trachurus) and European Hake (Merluccius merluccius) in the Aegean Sea

Yıl 2018, Cilt: 35 Sayı: 2, 157 - 168, 15.06.2018

Tuğçe Şensurat Genç Muhammed Atamanalp Celalettin Aydın

https://doi.org/10.12714/egejfas.2018.35.2.08

Cited By: 2

Öz

More than fifty published on demersal trawl codend selectivity studies have been carried out in the Mediterranean waters of Turkey since the mid-1980s. In this study, in an attempt to enhance the size selectivity of three species in the Aegean Sea trawl fisheries, three 90o turned meshes codens were investigated. Experiments were carried out in the Kuşadası Bay of the Eastern Mediterranean, between 19 January and 29 March 2015 with commercial stern trawler. The meshes of tested codends were turned 90o , two of them have 44 mm mesh size with 300 and 150 meshes around codend circumferences (44T300 and 44T150). The other has 40 mm mesh size with 165 meshes around codend circumferences (40T165). Individual hauls and mean selectivity parameters were estimated by using the CC2000 and EC-Modeller softwares, respectively. The mean L50 values of 44T300, 44T150 and 40T165 were 17.5 ± 0.2 mm, 18.6 ± 0.1 mm and 17.1 ± 0.2 mm carapace length for shrimp, 16.4 ± 0.4 cm, 17.1 ± 0.4 cm and 14.8 ± 0.2 cm total length for horse mackerel, respectively. The pooled L50 values of, 12.8 ± 0.5 cm, 13.2 ± 0.6 cm and 12.1 ± 0.1 cm total length for hake. While there are no differences between L50 values of 40T165 and 44T300 for deepwater rose shrimp (p>0.05), there are significant differences for horse mackerel (p<0.05). The likelihood ratio test results showed that there were no significant differences among all codends for European hake. In conclusion, any effort such as using square mesh, turned mesh codends or halved the number of meshes in the codend to release immatures of some species, is probably to cause the loss of marketable sizes of other species in the Mediterranean. This economical loss of revenues is the essential concern of fishermen that prevents them using alternative codend designs, though such designs are technically applicable. Consequently, the losses of income caused by using T90 mesh codend and halving the number of meshes around codend circumference should also be investigated in future studies

Anahtar Kelimeler

demersal trawl, turned meshes, deepwater rose shrimp, horse mackerel, European hake, Aegean Sea

Ege Denizi’nde Derinsu Pembe Karidesi (Parapenaeus longirostris), İstavrit (Trachurus trachurus) ve Bakalyaro için (Merluccius merluccius) döndürülmüş ağ gözü torba seçiciliği

Öz

Türkiye’nin Akdeniz sularında 1980’lerin ortalarından beri demersal trol torba seçiciliği üzerine elliden fazla çalışma yürütülmüştür. Bu çalışmada Ege Denizi trol balıkçılığında 3 türün boy seçiciliğini geliştirmek için 3 farklı döndürülmüş ağ göz torbaları araştırılmıştır. Denemeler Doğu Akdeniz’de bulunan Kuşadası Körfezi’nde 19 Ocak ve 29 Mart 2015 tarihleri arasında ticari trol teknesiyle gerçekleştirilmiştir. Deneme torbalarının ağ gözleri 90o döndürülmüş olup ikisi 44 mm ağ göz boyunda, 300 ve 150 torba çevre göz sayısına sahiptir (44T300 ve 44T150). Diğer torba 165 çevre göz sayısına sahip 40 mm ağ göz boyundadır. Bireysel çekimler ve ortalama seçicilik parametreleri sırasıyla CC2000 ve EC-Modeller yazılımları kullanılarak hesaplanmıştır. Derinsu pembe karidesinin 44T300, 44T150 ve 40T165 torbalarında ortalama L50 değerleri sırasıyla 17,5 ± 0,2 mm, 18,6 ± 0,1 mm ve 17,1 ± 0,2 mm karapas boyu, istavritin 16,4 ± 0,4 cm, 17,1 ± 0,4 cm and 14,8 ± 0,2 cm total boydur. Bakalyaronun birleştirilmiş L50 değerleri 12,8 ± 0,5 cm, 13,2 ± 0,6 cm ve 12,1 ± 0,1 cm total boydur. Derinsu pembe karidesi için 40T165 ve 44T300’den elde edilen L50 değerleri arasında fark yokken (p>0,05), istavrit için önemli fark vardır (p<0,05). Olabilirlik oran test sonuçları bakalyaro için tüm torbalar arasında istatistiksel olarak önemli bir fark bulunamamıştır. Sonuç olarak Akdenizde bazı türlerin jüvenillerini serbest bırakmak için kare gözlü, döndürülmüş gözlü torba kullanma veya torba etrafındaki göz sayısını yarıya düşürme gibi çabalar, pazarlanabilir boydaki diğer türlerin kaybına neden olabilmektedir. Alternatif torbalar teknik olarak uygulanabilir olmalarına rağmen, ekonomik gelir kaybı balıkçıların torbaları kullanmalarını önleyen esas kaygıdır. Bu nedenle, T90 torba ve torba çevre göz sayısının yarıya indirilmesinin sebep olacağı gelir kayıpları gelecek çalışmalarda araştırılmalıdır. 

Anahtar Kelimeler

döndürülmüş torba, derinsu pembe karidesi, istavrit, bakalyaro, Ege Denizi, Demersal trol

Kaynakça

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