Length-based estimates of growth parameters, mortality rates, and recruitment of Astacus leptodactylus (Eschscholtz, 1823) (Decapoda, Astacidae) in unexploited inland waters of the northern Marmara region, European Turkey)

The growth parameters, mortality rates, and recruitment pattern of Astacus leptodactylus from an unexploited area in inland waters of the northern Marmara region were investigated based on length-frequency data using FISAT software. Specimens were collected during eight scientific samplings carried out between March 2005 and May 2006. The seasonalized Von Bertalanffy growth function was fitted to the length frequency data (n = 2434) with the following parameters: L-infinity = 80.8 mm, K = 0.405 year(-1), C = 1, and WP = 0.90. The study of functional regressions permits us to conclude that the growth of this population is allometric. Natural mortality (M) was estimated at 0.578 year(-1)and total mortality at 0.589 year(-1). The longevity of the crayfish was calculated as t (max) = 7.4 year. The recruitment pattern shows that there is peak recruitment in May and June. We also estimated the potential instantaneous fishing mortality coefficient at F = 1.53-1.63 year(-1), the instantaneous total mortality coefficient at Z = 2.11-2.21 year(-1), and the exploitation rate E = 0.72-0.73, all through the length-converted catch curve procedure using the length-frequency data of the fyke-nets of 32 mm polyamide (PA) mesh size (stretched mesh).