University Of Tasmania

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Increasing the precision of the daily egg production method; 2020’s remix of a 1980’s classic

journal contribution
posted on 2023-05-21, 02:38 authored by Timothy WardTimothy Ward, Grammer, GL, Ivey, AR, Smart, JJ, McGarvey, R

This paper reviews application of the Daily Egg Production Method (DEPM) to sardine (Sardinops sagax) off southern Australia between 1995 and 2019. Coefficients of variation (CVs) of estimates of spawning biomass (SB) were reduced from 23–59% to 8–12% by: (i) estimating mean daily egg production (P0), spawning fraction (S), and sex ratio (R) from all historical data rather than annually; and (ii) combining batch fecundity (F) and female weight (W) into a single parameter, relative fecundity (F′ = Total daily egg production was estimated most precisely from annual estimates of spawning area (A) and estimates of P0 obtained from historical data. Both S and R were estimated most precisely from historical data. Estimating W and F from historical data did not increase precision. F′ had lower CVs than both W and F, and was stable across years and a wide range of W. Findings demonstrate that A can be converted into a precise estimates of SB using estimates of P0, S, R, and F′ obtained from historical data. However, the possibility that DEPM parameters may change in the future cannot be discounted. Future monitoring should include annual estimation of P0 and periodic (e.g. 3–5 years) re-estimation of adult parameters.


Publication title

ICES Journal of Marine Science










Institute for Marine and Antarctic Studies


Academic Press Ltd Elsevier Science Ltd

Place of publication

24-28 Oval Rd, London, England, Nw1 7Dx

Rights statement

Copyright 2021 International Council for the Exploration of the Sea

Repository Status

  • Restricted

Socio-economic Objectives

Wild caught fin fish (excl. tuna)