Project number: 2014-026
Project Status:
Completed
Budget expenditure: $200,000.00
Principal Investigator: Timothy M. Ward
Organisation: SARDI Food Safety and Innovation
Project start/end date: 11 May 2014 - 9 Jan 2016
Contact:
FRDC

Need

A project to refine methods for estimating egg production in application of the DEPM is needed because:

1) spawning biomass estimates obtained using the DEPM are the key biological performance indicators in the SASF and SPF;

2) the DEPM is recognized as being imprecise and the main source of this imprecision is associated with estimation of mean daily egg production;

3) a range of field and statistical methods are used to estimate total daily egg production but there is no consensus about which approach is most appropriate for the range of circumstances that are encountered, with different methods currently used in the Americas, Europe and Australia.

Uncertainty in the method used to estimate the spawning biomass of Jack Mackerel off the east coast of Australia was raised as an issue of particular concern in the recent public debate associated with the introduction of a large factory trawler into the SPF.

That debate undermined public confidence in the stock assessment and management of the SPF and has the potential to undermine other fisheries species of small pelagic fishes.

Objectives

1. Compare the performance of current and developmental statistical methods for estimating egg production using long-term datasets for several species
2. Conduct simulations to formally evaluate the performance of different approaches to sampling and statistical analysis on estimates of egg production
3. Establish improved methods for estimating daily egg production in applications of the DEPM

Final report

ISBN: 978-1-876007-07-2
Authors: T.M. Ward J. Carroll G.L. Grammer C. James R. McGarvey J. Smart A. Ivey
Final Report • 2018-02-22 • 6.96 MB
2014-026-DLD.pdf

Summary

This project was undertaken to refine the application of the Daily Egg Production Method to Australia’s largest fishery, the South Australian Sardine Fishery and the Commonwealth Small Pelagic Fishery. Key findings and outcomes from this study include: 1) a new generalised egg staging method that has several advantages over previous egg staging systems; 2) refinements to methods used to identify samples where a zero count should be allocated to one or more egg cohorts; 3) identification of factors that cause the high levels of uncertainty associated with estimates of mean daily egg production (P0) and egg mortality (z); 4) confirmation that the log-linear model is the most precise method currently available for estimating P0 and z for Australian Sardine off South Australia; 5) a simulation model that can be used to evaluate the effects of key processes on the precision of estimates of P0 and z; and 6) recommendations to trial a new oblique plankton sampler that may improve the precision of future estimates of P0. These findings and outcomes will improve the ongoing application of the Daily Egg Production Method to small pelagic species as well as other species to which the method is being applied. 

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