SEX RATIO, LENGTH AND WEIGHT FREQUENCY OF FRESHWATER CRAYFISH (ASTACUS LEPTODACTYLUS) INHABITING IN ARAS DAM LAKE, IRAN

Abstract

Freshwater crayfish are one of the important commercially caught aquatic organisms. Their nutritional values are also considerably important. Crayfish are benthic organisms which spends most of their life on the bed of aquatic habitats. In the present study, sex ratio and some biometric characteristics of crayfish (Astacus leptodactylus) inhabiting in Aras dam lake was investigated seasonally between spring 2011 and winter 2012. The mean total length and weight for the crayfish were 106.26±12.9 mm and 38.79±15.5 g, respectively. The results revealed that only a 13.67% of the captured crayfish exceeded than the standard commercial size (120 mm) and only 19.9% of the samples had higher weight than the standard commercial weight (50 grams). The results also revealed that male crayfish slightly dominated in captured samples (male: female, 1.07:1). Under the light of this study, it can be concluded that decreased catch value and crayfish size in comparison to previous studies carried out last decade, A. leptodactylus has a critical condition in Aras dam lake. Therefore, it is thought that further researches on the conservation and improving stocking density of this species in Aras dam lake are urgently required

Keywords

• length-weight frequency
• sex ratio
• crayfish
• Astacus leptodactylus
• Aras dam lake

ARAS REZERVUAR (İRAN)’INDA YAŞAYAN TATLISU ISTAKOZU (ASTACUS LEPTODACTYLUS)’NUN CİNSİYET ORANI, UZUNLUK VE AĞIRLIK DAĞILIMI

Öz

Tatlısu ıstakozu (kerevit) ticari olarak avcılığı yapılan önemli krustasea türlerinden biridir. Bu canlıların besin değerleri de oldukça yüksektir. Kerevitler bentik organizmalar olup, yaşamlarının büyük bölümünü su ortamlarının tabanlarında geçirirler. Bu çalışmada, Aras baraj göletinde yaşayan Astacus leptodactylus’un 2011 ilkbaharı ile 2012 kış mevsimleri arasında cinsiyet oranı ve bazı biyometrik özellikleri araştırıldı. Kerevitlerin ortalama toplam uzunluğu ve ağırlığı sırasıyla 106,26±12,9 mm ve 38,79±15,5 g olarak bulundu. Bulgular, yakalanan kerevitlerden sadece %13,67’sinin standart ticari uzunluğun (120 mm) ve %19,9’unun standart ticari ağırlığın (50 g) üzerinde olduğunu gösterdi. Bulgular ayrıca, erkek bireylerin dişi bireylere oranının azda olsa daha yüksek olduğunu gösterdi (erkek: dişi, 1.07:1). Sonuç olarak, bu çalışmada elde edilen bulgular, Aras baraj göletinde daha önceden yapılan çalışmalarla karşılaştırıldığında, A. leptodactylus’un yakalanan miktarında ve yakalanan bireylerin büyüklüğünde azalmanın olduğunu, ortamda yaşayan kerevitin durumunun birkaç yıl öncesine göre daha iyi olmadığını, ortaya çıkarmaktadır. Bu nedenle, Aras baraj göletinde yaşayan A. leptodactylus’un korunması ve stok yoğunluğunun arttırılması için çalışmaların yapılmasının gerektiği düşünülmektedir. 

Anahtar Kelimeler

• uzunluk ağırlık frekansı
• cinsiyet oranı
• kerevit
• Astacus leptodactylus
• Aras baraj gölü

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