Seasonal and Sexual Variation in the Length–Weight Relationship of Narrow–Clawed Crayfish Pontastacus leptodactylus (Eschscholtz, 1823) in Eğirdir Lake (Isparta), Türkiye

Öz

The length–weight relationship (LWR) is a fundamental aspect of fish biology and fisheries science, providing critical insights into various biological and ecological evolutions, such as growth analysis, stock assessment, health,condition, and feeding habits.Therefore, accurately determining it is extremely important. This study was conducted in Eğirdir Lake in 2015 to determine the length-weight relationship of Türkiye's most important crayfish stock. Seasonal sampling (January, April, July, October) was performed using 200 fyke nets with different mesh sizes. The LWR was determined according to Le Cren (1951), and a t-test following Pauly (1984) was used to assess whether the b value differed from 3. The data were analysed using the R package "ggFishPlots (v 0.3.1)". In the study, 4033 crayfish with a total length ranging from 35.12 to 155.11 mm and a total weight between 1.20 and 130.80 g were evaluated. The sample comprised 56.90% (2295) female and 43.10% (1738) male crayfish, with a F:M ratio of 1:0.76. The evaluations revealed that female crayfish exhibited negative allometric growth in spring, summer, and autumn, while displaying isometric growth in winter. Male crayfish, on the other hand, showed positive allometric growth in spring, autumn, and winter, but isometric growth in summer. As a result, it was determined that the growth characteristics of crayfish varied by sex and season. In studies utilizing LWR parameters, it is believed that sampling during only one period of the year may lead to misleading results. Therefore, monthly or seasonal sampling would provide more accurate assessments.

Anahtar Kelimeler

• Allometric growth
• Isometric growth
• Growth patterns
• Growth types
• LWR
• Seasonal dynamics

Eğirdir Gölü (Isparta-Türkiye) Kerevit Pontastacus leptodactylus (Eschscholtz, 1823) Populasyonunda Boy-Ağırlık İlişkisindeki Mevsim ve Eşeye Bağlı Değişimler

Öz

Boy-ağırlık ilişkisi (LWR) balık biyolojisi ve balıkçılık biliminin temel bir bileşenidir ve büyüme analizi, stok değerlendirmesi, sağlık ve kondisyon, beslenme alışkanlıkları gibi çeşitli biyolojik ve ekolojik gelişmeler hakkında kritik bilgiler sağlamaktadır. Bu nedenle, doğru bir şekilde belirlenmesi son derece önemlidir. Bu çalışma, Türkiye'nin en önemli kerevit stoğunun boy-ağırlık ilişkisindeki eşey ve sezona bağlı değişikliklerin belirlenmesi amacıyla 2015 yılında Eğirdir Gölü'nde yürütülmüştür. Mevsimsel örnekleme (Ocak, Nisan, Temmuz, Ekim), farklı göz açıklıklarına sahip 200 pinter kullanılarak gerçekleştirilmiştir. LWR, Le Cren'e (1951) göre belirlenmiş ve b değerinin 3'ten farklı olup olmadığını belirlemek için t-testi kullanılmıştır (Pauly, 1984). Veriler “ggFishPlots (v 0.3.1)” R paketi kullanılarak analiz edilmiştir. Çalışmada, toplam boyları 35,12 - 155,11 mm ve toplam ağırlıkları 1,20 - 130,80 g arasında değişen 4033 kerevit değerlendirilmiştir. Örneklemin %56,90'ı (2295) dişi ve %43,10'u (1738) erkek kerevitlerden oluşmuş olup D:E oranı 1:0.76'dır. Değerlendirmeler, dişi kerevitlerin ilkbahar, yaz ve sonbaharda negatif allometrik büyüme sergilediğini, kışın ise izometrik büyüme gösterdiğini ortaya koymuştur. Erkek kerevitler ise ilkbahar, sonbahar ve kış aylarında pozitif allometrik büyüme gösterirken, yaz aylarında izometrik büyüme göstermiştir. Sonuç olarak, kerevitlerin büyüme özelliklerinin cinsiyete ve mevsime göre değiştiği belirlenmiştir. LWR parametrelerinin kullanıldığı çalışmalarda, yılın sadece bir döneminde örnekleme yapılmasının yanıltıcı sonuçlara yol açabileceği düşünülmektedir. Bu nedenle, aylık veya mevsimsel örnekleme daha doğru değerlendirmeler sağlayacaktır.

Anahtar Kelimeler

• Allometrik büyüme
• İzometrik büyüme
• Büyüme tipi
• Büyüme deseni
• LWR
• Sezonsal dinamikler

Kaynakça

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