However, given that surveys for refining the DEPM are undertaken at peak spawning months (Stratoudakis et al., 2006), POFs would so greatly outnumber atretic follicles in fish ovaries that there would be little confusion in distinguishing the two and thus would lead to a very minor bias in the duration of POF resorption.
The measurement of POF cross-sectional areas is not very time consuming and could be merged into the routine of histological analysis for DEPM analyses.
Nevertheless, the maximum range of 4-5[degrees]C that can be observed during sardine DEPM surveys off the Iberian Peninsula corresponds to a 12-15% maximum difference in the rate of resorption and thus to a maximum of 8 hours lag in the degree of POF degeneration.
In routine DEPM analyses, the measurement of POF cross-sectional areas could increase technical work, but not necessarily the precision in the estimates of the spawning fraction because females are again broken down into spawning nights as they were with the histological staging method.
This work was supported by the program PELAGICOS (PLE/13/00) funded by the Portuguese Ministry of Science and the National Sampling Plan for DEPM surveys funded by the European Union.
The DEPM estimation of spawning-stock biomass for sardine and anchovy.