The effect of oocytic atresia on fecundity estimates of the rabbit fish Siganus sutor (pisces:siganidae) of Kenyan marine inshore waters

In the strongly group-synchronized oocyte development of Siganus sutor the group of oocytes to be released in the following spawning is identified. The smallest size of oocyte belonging to this group was identified by the presence of cytoplasmic vacuoles in oocytes in histological sections. These vacuolated oocytes corresponded to oocytes of 150 mu m diameter obtained by treatment with Gilson's fixative. The mean number of such oocytes in stage 4 (late developing) ovaries was found to be 638,000. The proportion of these oocytes removed by atresia before spawning was determined on histological sections to be 5%. The corrected estimate of mean fecundity was thus 606,000 oocytes per spawning.