Determination of Size Selectivity of Traps for Blue Crab (Callinectes sapidus Rathbun, 1896) in the Mediterranean Sea

Abstract

This study investigates the effects of trap selectivity of various mesh size on escape success of the blue crab (Callinectes sapidus). The study was carried out Çamlık Lagoon of Yumurtalık Gulf in the Mediterranean Sea and total of 1051 blue crabs were caught by rectangular baited trap. Using traps constructed with 30, 35, 40, 45 and 50 mm square mesh the proportion of crabs escaping through each mesh size was measured for each half centimetre carapace width (CW) class. A logistic model was fitted to the size frequency data of the retained and escaped blue crabs for each mesh size in the experiment. L50 and selection range (SR) for the 30, 35, 40, 45 and 50 mm (bar length) square meshes tested in this study was 8.47 cm and 0.85 cm; 9.31 cm and 0.39 cm; 10.40 cm and 0.31 cm; 11.72 cm and 1.17 cm; 13.17 cm and 0.89 cm respectively. The 50 mm square mesh of the trap showed relatively better selectivity considering the size at 50% sexual maturity of blue crab Callinectes sapidus, and the high rate of immature escapers

Keywords

• Blue crab Callinectes sapidus
• Trap
• Size selectivity
• Mediterranean Sea

Akdenizde Mavi Yengeç (Callinectes sapidus Rathbun, 1896) Tuzaklarının Boy Seçiciliğinin Belirlenmesi

Öz

Bu çalışmada mavi yengeç (Callinectes sapidus)’in tuzaktan kaçma başarısı üzerinde çeşitli göz açıklığına sahip tuzakların seçicilik etkileri incelenmiştir. Araştırma Akdeniz’de Yumurtalık körfezi, Çamlık Lagününde yürütülmüş dikdörtgen şekilli yemli tuzaklar kullanılarak toplam 1051 adet mavi yengeç yakalanmıştır. 30, 35, 40, 45 ve 50 mm kare gözlü ağ ile donatılmış tuzaklarla her bir tuzaktan kaçan yengeçlerin oranı 0.5 cm lik karapaks genişlik (CW) sınıfında ölçülerek tespit edilmiştir. Denemede her göz açıklığı için tuzaklarda kalan ve kaçan mavi yengeçlerin boy frekans verilerine göre lojistik bir model kullanılmıştır. Araştırmada kullanılan 30, 35, 40, 45 ve 50 mm’lik kare gözlü ağların % 50 seçicilik boyu (L50) ve seçicilik aralığı (SR) sırasıyla 8.47 cm ve 0.85 cm; 9.31 cm ve 0.39 cm; 10.40 cm ve 0.31 cm; 11.72 cm ve 1.17 cm; 13.17 cm ve 0.89 cm olarak belirlenmiştir. Tuzaktan kaçan ergin olmayan mavi yengeçlerin yüksek oranı ve % 50 cinsi olgunluk boyu dikkate alındığında 50 mm’lik kare gözlü ağa sahip tuzak, diğer tuzaklara göre daha yüksek seçicilik göstermiştir.

Anahtar Kelimeler

• Mavi yengeç Callinectes sapidus
• Tuzak
• Boy seçiciliği
• Akdeniz

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