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Population dynamics of grey mullet, Liza (Liza) ramada (Risso, 1826) from the Middle Adriatic (Šibenik Bay)

Population dynamics and stock size assessment of grey mullet, Liza ramada (Risso, 1826) was studied to provide the information for population dynamic parameters of this species and the stock size assessment done by using different methods in the Šibenik Bay. A total of 768 grey mullet specimens in the Šibenik Bay were obtained from February to July 1984. Surrounding net for mullets was used. Fish were measured, weighed and sexed. A gonadosomatic index was examined as well. Age and growth parameters were compared using Ford-Walford plot and Powell-Wetherall method. Total (Z), natural (M) and fishing (F) mortality as well as survival (S) and exploitation rate (E) were computed. Stock size assessments and MSY were performed and compared using several methods.Total length of L. ramada specimens was in the range 28-51 cm and weight 171.5-993.1 g. The study of the sex during this period showed that the proportion of females (61.3%) exceeded that of the males (28.7%). The mean size of the first capture (lc) was 18.0 cm.The length (TL, cm)-weight (g) relationship was: W =0.0101 L 2.9379. The von Bertalanffy growth parameters estimated by Ford-Walford plot and Powell-Wetheral method from length frequency data, were: LĄ = 52.5 cm, K = 0.25 yr-1, t0 = -0.1, and LĄ = 52.7 cm, K = 0.3 yr-1, t0 = -0.05 respectively. The sustainable yield was estimated to be 69 tonnes by VPA method (FiSAT) i.e. 79 tonnes (1). The catch in 1984 was 62.499 tonnes.

Liza ramada; Population dynamics; Stock assessment; Adriatic Sea; Šibenik Bay

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