Estimation of mortality rates from tagging data for pelagic fisheries: analysis and experimental design

Funded Activity Summary

Data from conventional tagging experiments have been and are becoming increasingly important for providing estimates of mortality rates in the stock assessment of large pelagic fishery resources as they provide a powerful, and perhaps only, alternative to relying on CPUE indices of abundance. There is an extensive scientific literature on tag-recapture experiments; however, a comprehensive framework for the analysis and design of tagging experiments in the pelagic fishery context does not exist. This has meant that in the design phase of tagging experiments, it has not been possible to provide scientifically rigorous advice on matters such as the relative tradeoffs between the number of tags to release, the spatial/temporal distribution of tags and the levels of observer coverage (required for estimation of reporting rates and for estimating the size/age distribution of the commercial catches). In addition, a comprehensive analysis of the extensive data from past SBT tagging experiments (particularly those conducted in the 1990s) taking into account all of the major potential sources of heterogeneity has not been completed because of the lack of a comprehensive estimation framework. Thus, the full benefit of the large research investment from these experiments has not been realized. It is also anticipated that conventional tagging programs will be a major future source of assessment information in both the eastern and western tuna fisheries. As such, an appropriate framework for the design and analysis of tagging experiments is needed to ensure that the full value from both past and future experiments is realized. Finally, there is increasing data accumulating from archival tags. There is a need to understand the role, and the relative cost/benefits, that archival tags can contribute to the overall estimation of mortality rates to past and future conventional tagging experiments.

Objectives:
1. to provide a robust estimation framework for estimating mortality rates for tuna stocks from conventional tag recapture data including associated confidence intervals
2. to apply the estimation framework to tag recapture data for southern bluefin tuna
3. to utilize the estimation framework to provide guidance in the design of future tagging experiments - in particular to examine the trade-offs between the number of tags released, levels of observer coverage and spatial/temporal distribution of tags

Funded Activity Details

Start Date: 20-10-2002

End Date: 11-02-2006

Funding Scheme: Funding Scheme not available

Funding Amount: $179,061.00

Funder: Fisheries Research and Development Corporation

Research Topics

ANZSRC Field of Research (FoR)

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ANZSRC Socio-Economic Objective (SEO)

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Other Keywords

Cost | Mortality | Stock Assessment | Tagging

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