The selectivity of monofilament trammel nets used in catch of gilt head bream (Sparus aurata, Linneaus, 1758) in İskenderun Bay-Turkey

Abstract

Bu çalışmada, çipura (Sparus aurata) avcılığında kullanılan monofilament fanyalı uzatma ağlarında dört faklı göz genişliğinin seçiciliği araştırılmıştır (28, 30, 32 ve 34mm). Balıkçılık denemeleri Şubat 2005 -Mayıs 2006 tarihleri arasında İskenderun Körfezi'nde gerçekleştirilmiştir. Sparus aurata'nın seçiciliği, SELECT (Millar, 1992) metodu ile işleyen GİLLNET bilgisayar programı ile belirlenmiştir. Beş farklı model kullanılarak; normal location, normal scale, gamma, log-normal and bi-modal, kullanılarak eldeki verilere en uygun seçicilik eğrisi belirlenmiştir. En uygun model bi-modal fonksiyon olarak belirlenmiştir. Bi-modal seçicilik eğrisine göre elde edilen optimum boylar sırasıyla; 17.49cm, 18.74cm, 19.99cm ve 21.24cm'dir. Buna göre, minimum avlama boyu ile (17cm) karşılaştırıldığında 28, 30, 32 ve 34mm göz genişliklerindeki ağlar, İskenderun Körfezi'ndeki çipura stokları üzerinde herhangi bir av baskısı oluşturmamaktadır. Anahtar Kelimeler: Fanyalı uzatma ağı seçiciliği, Optimum ağ göz genişliği, İskenderun Körfezi, Sparus aurata * Correspondence to: Erhan AKAMCA, Çukurova Üniversitesi, Su Ürünleri Fakültesi, Bu çalışma Çukurova Üniversitesi Bilimsel Araştırma Projeleri tarafından SÜF2004BAP11 numaralı proje ile desteklenmiştir. Journal of FisheriesSciences.comAkamca ve ark., 4(1): 28-37 (2010) Journal abbreviation: J FisheriesSciences.com 29 Abstract:The selectivity of monofilament trammel nets used in catch of gilt head bream (Sparus aurata, Linneaus, 1758) in İskenderun Bay-TurkeyIn this study, the mesh selectivity of monofilament trammel nets used in catch of gilt head bream (Sparus aurata) was investigated using four different mesh sizes (28, 30, 32 and 34mm).Fishing trials were carried out in İskenderun Bay from February 2005 to May 2006. Selectivity on Sparus aurata was assessed using the SELECT method (Millar, 1992), implemented in the GILLNET software. Five different functional models; normal location, normal scale, gamma, log-normal and bi-modal were used to fit the selectivity curve to the catch data. It was shown that the bi-modal function was the best to fit the data. For the selectivity curves on the bimodal, the optimum lengths (100% retention probability for the 28, 30, 32 and 34mm mesh sizes) were obtained as 17.49cm, 18.74cm, 19.99cm and 21.24cm, respectively. Thus, considering the minimum allowable landing size (17cm), 28, 30, 32 and 34mm mesh sizes do not cause an over fishing on gilt head bream stocks in Iskenderun Bay, Turkey.

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“…The most productive net was that of 6 cm mesh size, whereas the worst was that of 9 cm. The best suitable model was the binormal model in terms of the modal deviances (Table 2), which is considered as the most suitable in cases of capturing fish in mesh by jamming, wrapping and trammeling and large length frequency ranges in captured fish (Akamca, Kiyağa, & Özyurt, 2010;Holt, 1963;Hovgård, 1996). In this study, we observed many cases of tangled fish captured from sharp teeth of the pike.…”

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“…The model that has greater standard deviation shows that the model in question is not appropriate to the obtained data (Park et al, 2004;Akamca et al, 2010). The most suitable model was chosen taking into account the lowest deviance value.…”

Antalya Körfezinde (Doğu Akdeniz) küçük ölçekli balıkçılıkta kullanılan 40 ve 44 mm fanyalı uzatma ağlarının av ve seçiciliği

“…However, there are only three published studies on trammel nets used in Turkish seas. The SELECT method was used to estimate the selectivity of trammel nets used for the five most economically important species, bogue (Boops boops), annular sea bream (Diplodus annularis), striped red mullet (Mullus surmuletus), axillary sea bream (Pagellus acarne) and blotched picarel (Spicara maena) in the northern Aegean Sea (Karakulak and Erk, 2008), the gilthead bream (Sparus aurata) in the İskenderun Bay (Akamca et al, 2010) and the common dentex (Dentex dentex) in the southern Aegean Sea (Aydın and Sümer, 2010). There is no published study on the size selectivity of either gill or trammel nets in the Antalya Bay.…”