Measuring batch fecundity using automated particle counting

Oocyte batch development and enumeration in the European anchovy (Engraulis encrasicolus)

“…The spawning batch starts to be easily distinguishable from the advanced nucleus migration phase (NM) (mean oocyte size: 0.24 mm 2 ) while hydrated oocytes (size bigger than 0.35 mm 2 ) are completely separated from the previous maturity stages. Such results appear comparable to other studies carried out in Atlantic waters for similar species (Sardina pilchardus); however, in the sardine, the spawning batch starts to separate in size at the beginning of yolk granule formation (Ganias et al, 2010). The difference in the pattern of oocyte dynamics may be due to differences in the spawning dynamics of the two species.…”

“…Oocyte size and number in each gonad were measured using a semi-automated digital image analysis procedure (Ganias et al, 2010). In brief, after converting ovarian whole mount images to 8-bit type and adjusting the threshold so as to distinguish oocytes from the background, oocytes were separated using a segmentation algorithm and measured for their area (in mm 2 ) using particle analysis (Fig.…”

“…1D). This allowed distinguishing the most advanced group (AG) from the less-developed groups (for more details on this analysis see Ganias et al, 2010). For the purposes of this study, oocyte size corresponds to the mean area of the advanced group.…”

“…The main problem with the use of non-hydrated stages in BF evaluations is that the identification of the spawning oocyte batch is rather difficult though direct microscopic observations -especially for the stages preceding final oocyte maturation -because their size and appearance is quite similar to other oocytes. In the last decades, several studies attempted to solve this problem through estimating the spawning batch as the most advanced mode in oocyte size frequency distributions derived from automated particle counting procedures (e.g., Ganias et al, 2010). This image analysis procedure which is able to recognize and measure target oocytes in digital images of ovarian whole mounts, was first introduced for measuring mean oocytes diameters for evaluating total fecundity in determinate spawners (Thorsen & Kjesbu, 2001).…”

“…Kurita & Kjesbu (2009) extended the applicability of this procedure to indeterminate spawners; however, estimates of total fecundity find no applicability in assessments of reproductive potential for such kind of spawners. More recently, Ganias et al (2010) showed the suitability of image analysis techniques for the measurement of BF in the Atlantic sardine, Sardina pilchardus, which opposite to total fecundity is a crucial parameter for the reproductive potential of indeterminate spawners. The application of this method allows increasing the number of samples used for BF estimates in DEPM applications, and appears to save both work and time.…”