Length-based Stock Assessment for the Data-poor Crayfish Fishery from the Eğirdir Lake, Turkiye

Abstract

In this study, a stock assessment of the Pontastacus leptodactylus (Eschscholtz, 1823) population in Egirdir Lake where Turkey's most important crayfish production center, was made. The study was carried out between June 2021 and May 2022 in the concept of length-based data-poor fisheries management. TropFishR R package was used in study due to pretty effective in analysing of the length-frequency (LFQ) data. As a result of monthly fishing trials, 14,919 crayfish were caught between 29.92 and 163.38 mm in total length (14.83 – 80.95 mm carapace length). The female-male ratio of the population was found to be 1:1.21. It was determined that growth occurred (+) allometrically in all sexual groups (female, male, female+male). The growth parameters L∞, K and Ф of the P. leptodactylus stock were found to be 86.06-mm, 0.59/year, and 3.64, respectively. The annual rate of total (Z), natural (M) and fishing mortality (F) were estimated to be 3.02, 0.64, and 2.38/ year, respectively. The exploitation rate (E) of the crayfish stock was estimated to be 0.78, Fcurr/Fmax ratio 1.79 and SPR ratio 0.13. In this context, Egirdir Lake P. leptodactylus stock was evaluated as overfished. To ensure the sustainability of the stock of the species in the lake, it is necessary to reduce the mortality rate caused by fishing.