i) The variation in the stage-specific oocyte size frequency distribution during the annual reproductive cycle A distinct hiatus separating the yolked oocyte stock from the reservoir of unyolked oocytes, typical of synchronous and group-synchronous species, indicates that annual fecundity is determinate, whereas the lack of a hiatus may indicate that annual fecundity is indeterminate However, the lack of a hiatus does not necessarily indicate that fecundity is indeterminate (Hislop and Hall, 1974; using captive fish experiments)