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

Vollständiger Abstract

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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