Length-composition-based estimation of selected population parameters for incidentally captured endangered Black Sea sturgeons: an animal-welfare-oriented assessment of Acipenser stellatus and Acipenser gueldenstaedtii

Abstract

Sturgeons are among the most threatened groups of fishes worldwide, and the remaining Black Sea populations are a high-priority conservation concern because of their long lifespans, delayed maturity, anadromous migrations, historical overexploitation, habitat fragmentation, and persistent incidental capture. This study provides a length-composition-based assessment of selected population parameters for two endangered species the stellate sturgeon Acipenser stellatus and Russian sturgeon Acipenser gueldenstaedtii incidentally captured along the Black Sea coast of Türkiye. Records were compiled across eight years from 2016 to 2024 during commercial small-scale and industrial fishing operations and scientific fishery surveys in the Ordu–Samsun–Sinop–Kastamonu coastal region. The study was observational and animal-welfare-oriented: sturgeons were not targeted, live individuals were handled only when rapid documentation could be completed without compromising release, and analyses relied on unavoidable bycatch records. Total length and body weight were measured to the nearest 1 mm and 0.5 g, respectively. Length–weight relationships, Fulton’s condition factor, asymptotic length, growth coefficient, total mortality, natural mortality, fishing mortality, and exploitation ratio were estimated using standard length-based approaches. Acipenser stellatus ranged from 28.8 to 124.9 cm TL and 157 to 8,969 g, whereas A. gueldenstaedtii ranged from 34.4 to 148.8 cm TL and 505 to 10,955 g. The 60–80 cm length classes dominated both samples. Estimated exploitation ratios were high (E = 0.69 and 0.65, respectively), indicating biologically meaningful incidental fishing pressure on populations with restricted recovery capacity. The results support precautionary bycatch reduction, mandatory live-release protocols, fisher training, improved reporting, and integration of length-based indicators into Black Sea sturgeon recovery programs. Keywords: Acipenser stellatus, Acipenser gueldenstaedtii, endangered species, incidental catch, animal welfare, Black Sea

Keywords

• Acipenser stellatus
• Acipenser gueldenstaedtii
• endangered species
• incidental catch
• animal welfare
• Black Sea

Karadeniz’de tesadüfi olarak avlanan nesli tehlike altındaki mersin balıklarında boy kompozisyonuna dayalı bazı populasyon parametreleri tahmini: Acipenser stellatus ve Acipenser gueldenstaedtii için hayvan refahı odaklı bir değerlendirme

Abstract

Mersin balıkları dünya genelinde en fazla tehdit altında bulunan balık gruplarından biridir. Uzun ömürleri, geç eşeysel olgunluğa ulaşmaları, anadrom göçleri, tarihsel aşırı avcılık, habitat parçalanması ve süregelen tesadüfi av baskısı nedeniyle Karadeniz’de kalan popülasyonlar yüksek öncelikli bir koruma sorunu oluşturmaktadır. Bu çalışmada, Türkiye’nin Karadeniz kıyıları boyunca tesadüfi olarak avlanan iki nesli tehlike altındaki türün—sivri burun mersin balığı Acipenser stellatus ve Rus mersin balığı Acipenser gueldenstaedtii—boy kompozisyonuna dayalı seçilmiş popülasyon parametreleri değerlendirilmiştir. Kayıtlar, Ordu–Samsun–Sinop–Kastamonu kıyı bölgesinde küçük ölçekli ve endüstriyel ticari balıkçılık faaliyetleri ile bilimsel balıkçılık araştırmaları sırasında 2016–2024 arasındaki sekiz av sezonunda derlenmiştir. Çalışma gözlemsel ve hayvan refahı odaklı olarak yürütülmüş; mersin balıkları hedeflenmemiş, canlı bireyler yalnızca hızlı belgeleme işlemleri salıverilmelerini tehlikeye atmadığında ele alınmış ve analizler kaçınılmaz yan av kayıtlarına dayandırılmıştır. Total boy ve vücut ağırlığı sırasıyla 1 mm ve 0,5 g duyarlılıkla ölçülmüştür. Boy–ağırlık ilişkileri, Fulton kondisyon faktörü, asimptotik boy, büyüme katsayısı, toplam ölüm, doğal ölüm, balıkçılık ölümü ve sömürülme oranı standart boya dayalı yaklaşımlarla tahmin edilmiştir. Acipenser stellatus 28,8–124,9 cm total boy ve 157–8.969 g; A. gueldenstaedtii ise 34,4–148,8 cm total boy ve 505–10.955 g aralığında bulunmuştur. Her iki örneklemde de 60–80 cm boy sınıfları baskındır. Tahmin edilen sömürülme oranlarının yüksek olması (sırasıyla E = 0,69 ve 0,65), iyileşme kapasitesi sınırlı popülasyonlar üzerinde biyolojik açıdan anlamlı bir tesadüfi av baskısına işaret etmektedir. Bulgular; ihtiyatlı yan av azaltımı, zorunlu canlı salıverme protokolleri, balıkçı eğitimi, geliştirilmiş raporlama ve boya dayalı göstergelerin Karadeniz mersin balığı iyileştirme programlarına dâhil edilmesini desteklemektedir. Anahtar Kelimeler: Acipenser stellatus, Acipenser gueldenstaedtii, nesli tehlike altındaki türler, tesadüfi av, hayvan refahı, Karadeniz

Keywords

• Acipenser stellatus
• Acipenser gueldenstaedtii
• nesli tehlike altındaki türler
• tesadüfi av
• hayvan refahı
• Karadeniz

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