The underlying concept for egg production methods is very
simple; if we know how many eggs have been spawned over a period of time (e.g. daily or annually) in the spawning area, and
we know how many eggs an average individual mature female can
produce over the same period, then we can estimate the size of the
spawning population. This simple concepts different from another
concept in fisheries science: the production of recruits, when the
number of eggs spawned is linked to the next generation entering
the population. Some of the data gathered for EPMs can be
used for understanding recruitment and this has been often used in
defence of EPMs (Lasker, 1985; Castro et al., 2005; Van fer Lin gen
and Huggett, 2003). However, most EPM surveys are not usually
designed to analyse recruitment processes.