Egg Production Method for Estimating Spawning Biomass of Pelagic Fish: Application to the Northern Anchovy, 'Engraulis mordax'

摘要

The spawning fraction of multiple spawners is estimable when females exhibit morphological characteristics which indicate when spawning will take (or has taken) place. The length of time in which characteristics remain detectable must in itself be estimable and constant over the field sampling interval. Spawning biomass is then estimated as a function of the estimated spawning frequency and other parameters: egg production, batch fecundity, sex ratio, and average weight of mature females. Based on the delta method, approximate variance estimates for spawning biomass are derived and given.