Age and growth of horse mackerel, Trachurus trachurus (L.), in the Gulf of Saronikos (Greece)

The age and growth of horse mackerel, Trachurus trachurus (L.), were studied in the Gulf of Saronikos (Greece) during the years 1989-1991. Length frequency based on a total of 6791 specimens was followed by month, while age reading was undertaken on 2390 otoliths. The 1st annulus formation was detected comparing the progression by month of the smaller modal fish length with the respective otolith appearance during the year. Annuli were easily readable until the 5th ring, but in older fish the otoliths became thick and the annuli appeared very close to each other. The time of hyaline annual zone completion was estimated by the study of monthly marginal increments. This time was found to be around the end of the year and coincides with the prespawning period. Mean weight per age was studied during the year, showing that growth in weight was seasonal for adult fish and continuous for juveniles. Mean lengths at age from otolith reading in the monthly samples were applied to the yon Bertalanffy equation and growth parameters were estimated: L(inf) = 30.27 cm. k = 0.366, t(o) = -0.943. The same values of growth parameters were found fitting the growth equation to the back calculated fish lengths at age. By studying the growth curve it was observed that horse mackerel had fast growth during the first years of life. This seems to be a general characteristic of the most species in eastern Mediterranean.