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 s tudied in the Gulf of Saronikos (Greece) during the years 1989-1991. L ength frequency based on a total of 6791 specimens was followed by mon th, while age reading was undertaken on 2390 otoliths. The 1st annulus formation was detected comparing the progression by month of the smal ler modal fish length with the respective otolith appearance during th e year. Annuli were easily readable until the 5th ring, but in older f ish the otoliths became thick and the annuli appeared very close to ea ch other. The time of hyaline annual zone completion was estimated by the study of monthly marginal increments. This time was found to be ar ound the end of the year and coincides with the prespawning period. Me an 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 applie d to the von Bertalanffy equation and growth parameters were estimated : L-inf = 30.27 cm, k = 0.366, t(0) = -0.943. The same values of growt h parameters were found fitting the growth equation to the back calcul ated fish lengths at age. By studying the growth curve it was observed that horse mackerel had fast growth during the first years of life. T his seems to be a general characteristic of the most species in easter n Mediterranean. (C) 1997 Elsevier Science B.V.