Project number: 2009-066
Project Status:
Completed
Budget expenditure: $46,250.00
Principal Investigator: Jeremy D. Prince
Organisation: Biospherics Pty Ltd
Project start/end date: 31 Jan 2010 - 29 Nov 2010
Contact:
FRDC

Need

The GVP of the gummy shark fishery is approximately $13 million comprising 15-20% of the SESSF. The fishery has a history of stable catches which successive analyses show is due to stable recruitment since the targeted fishery began in the early 1970s. Little research has been conducted on gummy sharks because its stability has made it difficult to justify. However, the fishery displays a number of unusual, and poorly understood dynamics which conflict with standard stock assessment assumptions making estimates of adult biomass highly uncertain. The adoption of the Commonwealth Harvest Strategy Policy (HSP) mandating managing to a default 48% of virgin biomass places the gummy shark fishery in a difficult position. Its quantitative assessment estimates adult biomass to be around 40% (albeit arbitrarily). So despite catch rates, effort and body size at 1970s levels, and all analyses showing stable virgin recruitment, applied literally to unreliable estimates of adult biomass, the HSP will necessitate a >30% reduction in the TAC and result in an unwarranted 5-7% loss of GVP to the SESSF. There is also growing public concern at the general unsustainability of most shark fisheries and it can be predicted that the gummy shark fishery will be subject to increasingly strident demands to prove its sustainability.

In this policy environment the existing stock assessment, with its acknowledged weaknesses is a liability. The need is to fundamentally redesign and redevelop the harvest strategy for gummy shark explicitly accounting for its unusual dynamics. This new approach needs to be based on empirical indicators of the fishery (catch, effort, cpue, size/age structure) which have allowed recruitment trends to be robustly estimated, rather than unreliably modeled trends in adult biomass. Importantly this new empirical approach needs to be justified with robust science so that this fishery can be distinguished from unsustainable shark fisheries.

Objectives

1. Develop a new harvest strategy for gummy shark fishery based on empirical indicators derived from simple data collected from the fishery.
2. Synthesize existing fisheries and biological data pertaining to the new harvest strategy and document the scientific rationale for the new harvest strategy.
3. Identify critical gaps in information needed to support the new approach and outline and scope the data collection systems, biological research and modelling studies needed to fill the critical gaps identified.

Final report

ISBN: 978-0-9804479-2-7
Author: Jeremy Prince

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