Effect of twine thickness on size selectivity and catch efficiency of gillnets used in Prussian carp (Carassius gibelio) fisheries

Tuncay Ateşşahin; Mehmet Cilbiz; Mahmut İlhan

doi:10.12714/egejfas.43.1.04

EN TR

Effect of twine thickness on size selectivity and catch efficiency of gillnets used in Prussian carp (Carassius gibelio) fisheries

Abstract

This study evaluated the effects of twine thickness and mesh size on the size selectivity and catch efficiency of gillnets used to control the invasive Prussian carp, Carassius gibelio (Bloch, 1782) population in the Karakaya Dam Lake, Türkiye. A total of 1.675 individuals ranging from 17.0 to 31.2 cm in length were captured. Among the tested configurations, the gillnet with 84 mm mesh size and 0.23 mm twine thickness demonstrated the highest catch efficiency, accounting for 50.4% of the total catch, whereas the 76 mm mesh with 0.18 mm twine yielded only 17.9%. Statistical analysis confirmed that mesh size significantly influenced the average length of captured fish (p < 0.05), with larger mesh sizes capturing longer individuals. Seasonal variation was notable, with peak catches observed in December (375 specimens) and January (316 specimens), aligning with the winter schooling behaviour of the species that enhances catchability. The SELECT method was used to model size selectivity, and the lognormal model provided the best fit across all twine thicknesses. Modal lengths of 20.59 cm (0.23 mm), 20.97 cm (0.20 mm), and 21.64 cm (0.18 mm) were estimated, indicating minimal variation due to twine thickness. Although twine thickness did not significantly affect selectivity, it enhanced catch efficiency, particularly for larger individuals. These findings suggest that gillnets with thicker twine and larger mesh sizes are more effective for managing C. gibelio populations, especially during winter months. Moreover, the use of durable gear contributes to reduced gear loss and increased operational lifespan, supporting the socioeconomic sustainability of local fisheries. This research provides a scientific foundation for developing seasonally optimized and gear-specific strategies for managing invasive species in Turkish inland waters.

Keywords

Sade uzatma ağlarında farklı ip kalınlığındaki sade ağ kullanımının gümüşi havuz balığı (Carassius gibelio) avcılığında boy seçiciliği ve av verimi üzerindeki etkileri

Öz

Bu çalışmada, Karakaya Baraj Gölü'ndeki (Malatya, Türkiye) istilacı gümüşi havuz balığı, Carassius gibelio (Bloch, 1782) popülasyonun avcılık ile kontrol edilebilmesine yönelik olarak, farklı ip kalınlığı ve ağ göz açıklığındaki sade uzatma ağı kullanımının avın boy seçiciliği ve verimliliği üzerindeki etkileri araştırılmıştır. Çalışmada 17,0-31,2 cm toplam boy aralığında 1.675 birey yakalanmıştır. Test edilen konfigürasyonlar arasında, 84 mm ağ gözü açıklığına ve 0,23 mm ip kalınlığına sahip sade ağ, toplam avın %50,4'ünü oluşturarak en yüksek av verimliliğini göstermiş; buna karşın 76 mm ağ gözü açıklığına ve 0,18 mm ip kalınlığına sahip ağ yalnızca %17,9 verim sağlamıştır. İstatistiksel analiz, ağ gözü açıklığının yakalanan balıkların ortalama uzunluğunu önemli ölçüde etkilediğini (p<0,05) ve daha büyük ağ gözü açıklıklarının daha uzun bireyleri yakaladığını doğrulamıştır. Mevsimsel farklılık dikkat çekici olup, en yüksek av Aralık (375 örnek) ve Ocak (316 örnek) aylarında elde edilmiştir. Bu durum, türün avlanabilirliğini artıran kış dönemi sürü oluşturma davranışı ile uyumludur. Ağların boy seçiciliğinin modellenmesinde SELECT yöntemi kullanılmış ve lognormal model, tüm ip kalınlıkları için en iyi uyumu sağlamıştır. İp kalınlığından kaynaklanan minimum varyasyonu gösteren model uzunluklar sırasıyla 20,59 cm (0,23 mm), 20,97 cm (0,20 mm) ve 21,64 cm (0,18 mm) mm olarak tahmin edilmiştir. İp kalınlığı seçiciliği önemli ölçüde etkilemese de, özellikle daha büyük bireyler için av verimliliğini artırmıştır. Bu bulgular, daha kalın ipli ve daha büyük ağ gözü açıklığına sahip sade ağların, özellikle kış aylarında C. gibelio popülasyonlarını avlamada daha etkili olduğunu göstermiştir. Ayrıca, dayanıklı av araçlarının kullanılması, av aracı kaybının azalmasına ve operasyonel ömrün uzamasına katkıda bulunarak yerel balıkçılığın sosyoekonomik sürdürülebilirliğini desteklemektedir. Bu araştırma, Türkiye iç sularındaki istilacı türlerin yönetimi için mevsime göre optimize edilmiş ve av aracına özgü stratejiler geliştirilmesi adına bilimsel bir temel sunmaktadır.

Anahtar Kelimeler

Supporting Institution

Fırat University Scientific Research Project No: SÜF.23.03

Project Number

SÜF.23.03

Ethical Statement

No specific ethical approval was necessary for the study.

Thanks

This study is based on part of the third author's master's thesis “Investigation of extension gillnet properties for put under pressure of invasive Carassius gibelio species in Karakaya Dam Lake”. This study was supported by the Fırat University Scientific Research Project SÜF.23.03

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Details

Primary Language

English

Subjects

Freshwater Ecology , Post-Harvest Fisheries Technologies (Incl. Transportation) , Fisheries Management

Journal Section

Research Article

Authors

Tuncay Ateşşahin ^*
0000-0001-9168-5444
Türkiye

Mehmet Cilbiz
0000-0002-7686-7570
Türkiye

Mahmut İlhan
0000-0001-7485-5149
Türkiye

Publication Date

February 18, 2026

Submission Date

November 25, 2025

Acceptance Date

December 23, 2025

Published in Issue

Year 2026 Volume: 43 Number: 1

DOI

https://doi.org/10.12714/egejfas.43.1.04

IZ

https://izlik.org/JA25ZP29XU

Cite

RIS / Bibtex

APA

Ateşşahin, T., Cilbiz, M., & İlhan, M. (2026). Effect of twine thickness on size selectivity and catch efficiency of gillnets used in Prussian carp (Carassius gibelio) fisheries. Ege Journal of Fisheries and Aquatic Sciences, 43(1), 29-40. https://doi.org/10.12714/egejfas.43.1.04