Determinate versus indeterminate fecundity in horse mackerel

Abstract No consensus has been reached yet on the question whether horse mackerel has a determinate or an indeterminate fecundity. This problem has been discussed based on three main criteria: (a) oocyte size frequency distribution, (b) the number of yolked oocytes in the ovary and (c) atresia. The analysis of the oocyte size frequency distribution showed that no distinct hiatus could be observed between pre-vitellogenic and vitellogenic oocytes. The number of yolked oocytes in the ovary was found higher in imminent spawning ovaries than in the pre-spawing, while a greater number of late yolked oocytes was found in recently spawning ovaries than in the pre-spawning. High incidence of atresia was also found in recently spawning (6–22%) and spent ovaries (over 29%). Those findings indicate that horse mackerel has most probably an indeterminate fecundity.