Three and a half decade analysis of fish biodiversity in İzmir Bay, western Aegean Sea: Insights into fishing methods and habitat changes

Öz

This study evaluates the biodiversity of fish species caught using different fishing methods in relation to habitat distribution, based on 34 length-weight studies conducted in İzmir Bay between 1990-2024. The obtained data has been analysed in terms of traditional and modern fishing methods' species distributions in coastal and offshore habitats and the state of the bay ecosystem. This study examines how fish species diversity in the bay fluctuates over time, analyzing the impact of habitat characteristics and fishing practices on these variations. In the study, data from 170,466 fish specimens belonging to 139 species were analyzed using the Biodiversity Pro program. According to Simpson’s Reciprocal Index analysis, trawling is the most dominant fishing method with 20.81% in terms of number of individuals, followed by trammel net with 13.12%. While trawling, the bay's most effective fishing gear, catches 97 species, trammel net catches 28 species. The fishing method capturing the least number of individuals is fishnet with 1%. According to life forms, demersal species constitute the dominant group (18.157%) in the bay, while bathypelagic species showed the lowest diversity (1%). According to the Margalef index, the highest species richness was observed in demersal species (M: 28.265), while the lowest was in bathydemersal species (M: 43.792). According to studies between 1990-2024, fish populations with a b value above 3 comprise 68.61% in İzmir Bay. The average b value of 3.078 indicates that fish populations in the bay consist of species prone to positive allometric growth. The findings provide important contributions to understanding the ecological preferences of fishing methods and fish species. These data offer significant recommendations for sustainable fishery and species diversity management in İzmir Bay.

Anahtar Kelimeler

• Biodiversity
• Fish populations
• Fishing methods
• İzmir Bay
• Aegean sea

Batı Ege Denizi'ndeki İzmir Körfezi'nde balık biyolojik çeşitliliğinin otuz beş yıllık analizi: Balıkçılık yöntemleri ve habitat değişikliklerine ilişkin görüler

Öz

Bu çalışma, 1990-2024 yılları arasında İzmir Körfezi'nde gerçekleştirilen 34 adet boy-ağırlık çalışmasına dayanarak, farklı balıkçılık yöntemleriyle avlanan balık türlerinin biyolojik çeşitliliğini habitat dağılımı ile ilişkili olarak değerlendirmektedir. Elde edilen veriler, geleneksel ve modern balıkçılık yöntemlerinin kıyı ve açık deniz habitatlarındaki tür dağılımları ve körfez ekosisteminin durumu açısından analiz edilmiştir. Bu çalışma, körfezdeki balık türlerinin çeşitliliğinin zaman içinde nasıl değiştiğini inceleyerek, habitat özelliklerinin ve balıkçılık uygulamalarının bu değişiklikler üzerindeki etkisini analiz etmektedir. Çalışmada, 139 türe ait 170.466 balık örneğinin verileri Biodiversity Pro programı kullanılarak analiz edilmiştir. Simpson'ın Karşılıklı Endeks analizine göre, trol balıkçılığı, birey sayısı açısından %20,81 ile en baskın balıkçılık yöntemidir ve onu %13,12 ile tramell ağ izlemektedir. Körfezin en etkili balıkçılık aracı olan trol balıkçılığı 97 tür yakalarken, tramell ağ 28 tür yakalamaktadır. En az birey yakalayan balıkçılık yöntemi ise %1 ile balık ağıdır. Yaşam formlarına göre, demersal türler körfezde baskın grubu oluştururken (%18,157), batipelajik türler en düşük çeşitliliği göstermiştir (%1 Margalef indeksine göre, en yüksek tür zenginliği demersal türlerde (M: 28,265) gözlemlenirken, en düşük tür zenginliği batidemersal türlerde (M: 43,792) gözlemlenmiştir. 1990-2024 yılları arasında yapılan çalışmalara göre, İzmir Körfezi'nde b değeri 3'ün üzerinde olan balık popülasyonları %68,61'i oluşturmaktadır. 3,078 olan ortalama b değeri, körfezdeki balık popülasyonlarının pozitif allometrik büyümeye eğilimli türlerden oluştuğunu göstermektedir. Bu bulgular, balıkçılık yöntemlerinin ve balık türlerinin ekolojik tercihlerini anlamaya önemli katkılar sağlamaktadır. Bu veriler, İzmir Körfezi'nde sürdürülebilir balıkçılık ve tür çeşitliliği yönetimi için önemli öneriler sunmaktadır.

Anahtar Kelimeler

• Biyoçeşitlilik
• Balık populasyonları
• Avcılık metodu
• İzmir Körfezi
• Ege Denizi
• Türkiye
• Türkiye

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