Seasonal size distribution, condition status and muscle yield of Mediterranean horse mackerel Trachurus mediterraneus from the North Aegean Sea, Greece

The seasonal intrinsic variability of the North Aegean Sea Mediterranean horse mackerel Trachurus mediterraneus population has been studied from monthly samples taken from the Greek purse-seine fishery over a 4-year period (2001-2005). The length and weight frequency distributions differed significantly by season, the highest mean lengths and weights attained in spring and the lowest in autumn. Length-weight relationships were determined on a monthly and annual basis, and monthly variations on the allometry coefficient were found. The differences between the coefficient obtained for annual data and the coefficients for each month were not significant in 50% of the cases. The b-values obtained both in this study and some of the previously reported in the Mediterranean Sea and other Greek waters were compared, showing basic similarities and minor spatial variation. The seasonal cycle in Mediterranean horse mackerel condition appears to be related to the reproductive cycle of the fish. Values of muscle yield ranged between 23.33% and 33.07% (mean value 28.48 +/- 2.49%), but variations within seasons were not significant.