Measuring batch fecundity using automated particle counting

We present an automated procedure which uses micrographs of ovarian whole mounts to recognize, separate and count the oocytes of the spawning batch with the aim to provide estimates of batch fecundity. The method was applied in the Atlantic sardine, Sardina pilchardus, and was tested in both hydrated and non-hydrated females. At a first step, automated particle counting was validated in hydrated ovaries given that at this stage differentiation both in size and shape of the spawning batch is large enough to guarantee its accurate visual identification. Next, using oocyte size frequency distributions at sequential developmental stages it was shown that the advanced batch separates in size from the subsequent batches at the secondary yolk stage with a gap being established when it reaches an average size of ca. 0.13 mm2. Based on this result the automated method was applied to females between the secondary yolk stage and the migratory nucleus stage and the results were compared to those from hydrated females. The estimated relationship of batch fecundity versus gutted weight did not differ significantly between the two groups of females which indicated the accuracy of the method and its suitability in batch fecundity estimations whenever hydrated females are scarce or even absent.