Biological parameters of Mediterranean horse mackerel, Trachurus mediterraneus (Steind.) in the eastern Adriatic

Background and Purpose: Mediterranean horse mackerel, Trachurus mediterraneus, is distributed throughout the Mediterranean, the Black Sea, and the north-eastern Atlantic. In the Mediterranean Sea it is of major importance in the pelagic and demersal fisheries. Despite its economical importance, biological data about Mediterranean horse mackerel are very limited. The aim of the present study was to give some new information on age and growth rate of Mediterranean horse mackerel collected in the eastern Adriatic Sea. Material and Methods: Random samples of 1415 individuals caught in the easternAdriatic Sea during the period May 1996 to April 1997 were used for the study of length-weight relationship. The commonly used length-weight relationship W = aL(b) was applied. Age and growth rate were analyzed for 1019 specimens collected during the spawning season (May-July, 1996). Age was determined by sagitta otolith reading. Length and age data were used to estimate growth parameters (Linfinity, K, t(o)) of von Bertalanffy growth equation. Results and Conclusion: The values of b in length-weight relationship for males (b = 3.125) and females (b = 3.157) indicated slightly positive allometric growth, i.e. slightly faster in weight than in length. The growth of total samples (males, females and immature specimens) was isometric (b = 2.997), i.e. it was proportionally equal for the length and weight. Age ranged from 1-8 years, Growth parameters for males (Linfinity = 38.11, K = 0.204, t(o)= -0.54), females (Linfinity = 39.00 K=0.211, t(o) = -0.56) and total sample (Linfinity = 39.13, K = 0.224, t(o) = - 0.35) were calculated.