SPAWNING FREQUENCY AND BATCH FECUNDITY OF HORSE MACKEREL, TRACHURUS-TRACHURUS (L.), IN THE SARONIKOS GULF (GREECE)

Horse mackerel, Trachurus trachurus (L.), is a multiple spawning fish with most probably an indeterminate fecundity. Histological sections o f gonads were used to identify the hydrated oocytes, the migratory-nuc leus stage oocytes, and the new and old post-ovulatory follicles. Spaw ning frequency determination, based on the mean percentage estimation of the females that occurred in different spawning states such as migr atory-nucleus stage oocytes and post-ovulatory follicles during two su ccessive reproductive periods, was found to average once every 5.8 and 4.8 days, respectively. High spawning frequency was observed at the p eak of spawning. Relative batch fecundity of 205 oocytes/g fish weight was estimated by the hydrated and migratory-nucleus method. Since pot ential annual spawnings were found to be equal to 16, potential annual relative fecundity could be 3280 oocytes/g fish weight.