Project number: 2004-022
Project Status:
Budget expenditure: $495,501.00
Principal Investigator: Cathy M. Dichmont
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 30 Mar 2005 - 31 Aug 2008


Management arrangements for the NPF tiger prawn fishery are currently chosen so that the spawning stock biomass should recover to the level at which Maximum Sustainable Yield, MSY, is achieved with more than 70% certainty by 2006. MSY is a management reference point that is based solely on biological considerations. From an economic point of view (one that seeks to maximize economic efficiency and fishery returns) this target is inappropriate. The current rebuilding strategy implies that the NORMAC may, over time, be able to reassess the present harsh management measures instituted in the NORMAC agreed effort reduction program in 2001. However, in recent years it has become clear that the fishery is unable to wait for prawn recovery without addressing economic efficiency. NORMAC has identified an urgent need for a further fishery restructure (without compromising biological recovery) so as to maintain economic sustainability and profitability.

An immediate need is for this project to quantify the size of the fleet and length of the season given the biology of ALL the prawn resources. At present it is only broadly possible to answer this question if prawns other than tiger prawns and within year dynamics are ignored (which is unacceptable).

Additionally, this prawn fishery still needs to keep track of its fishing impacts. The main method in the past, with much success, has been through bycatch reduction by TEDs and BRDs. It is now possible, also to include fishing impacts in the modelling mechanisms to allow broader and better informed decision making.

Management advice provided by the NPF Assessment Group needs to take account of the impacts on the stock, economic efficiency and the ecosystem. Input controls are such that several different combinations of fleet size, gear size and season length can produce the same biological outcome but these options would not be equally economically efficient. It is not only overall effort levels that matter for economic efficiency but the manner in which vessels combine inputs in harvest that matters for economic efficiency. This decision over input combinations is sensitive to management decisions and as yet there is no clear economic evaluation of the fishery efficiency under current management practices in a combined biological and economic study.

Limit and target reference points, such as the MSY, in this fishery have only been investigated from the point of view of tiger prawn sustainability. It has been shown in other parts of the world that choosing management arrangements so that fishing effort corresponds to MSY does not necessarily lead to the highest profits and, in fact, lower effort levels generally lead to larger profits and more efficient outcomes. Furthermore, fishing below MSY may also benefit bycatch and byproduct species.

There is therefore a need that future stock assessment undertakes a holistic management view of this prawn fishery. Reference points and management advice should be aimed towards maximising economic return, while ensuring long term target species sustainability and minimising the impact of this fishery on other species wherever possible.

This can only be achieved by:
a) joining the databases held separately by AFMA, CSIRO and ABARE/ANU, and
b) combining the Management Strategy Evaluation frameworks produced by CSIRO on tiger prawns (FRDC 2001/002), ANU/ABARE on economic efficiency (FRRF) and CSIRO investigating effects of trawling on the seabed (FRDC 2002/102).


1. Construct a comprehensive and consistent combined data base for the NPF, by integrating the existing data held by CSIRO and ABARE data.
2. Develop an analysis technique that integrates stock assessment within an economic framework by combining features of the methods developed by ABARE/ANU and CSIRO to enable evaluation of economic efficiency and fishery returns.
3. Develop a basic ecosystem model that synthesises present knowledge about the NPF ecosystem that can be driven at spatial and temporal scales appropriate to stock assessment.
4. Extend the current Management Strategy Evaluation framework to include economic outputs and outputs related to the impact of the fishery on the ecosystem.
5. Evaluate alternative management decision rules for the NPF in terms of their impacts on stock sustainability, economic efficiency, economic returns and ecosystem impacts.

Final report

ISBN: 978-1-921424-13-7
Author: Catherine Dichmont

Related research


Understanding the relationship between commercial prawn species population dynamics, fishing patterns and climate in the Shark Bay World Heritage area in Western Australia

1. Understand the impact of changing temperature and other environmental parameters (e.g. seagrass, flooding events) on the reproductive cycles, growth and distribution patterns of western king and brown tiger prawns
Department of Primary Industries and Regional Development (DPIRD) WA