To assess whether the ESD and MEE objectives are met there is a need to determine the status of prawns stocks in the NPF and to develop guidelines to define whether the present status of the stocks may require management actions. It is important to precisely define what population parameters should be monitored and what biological reference points should these parameters be compared in order to determine whether management action is required. The Northern Prawn Fishery Assessment Group (NPFAG) has identified that spawning stock biomass and standardised fishing effort are the two most important indicators for target stocks in the NPF. The NPFAG has also established that targets and limits for these indicators need to be set and reassessed as new information is collected. The NPFAG has also recommended that future advice provided to them by researchers should include an explicit measurement of the probabilities that each of these targets may be exceeded. Calculation of such probabilities requires formal risk analysis to be carried out as part of the stock assessment.

Additionally, there are a number of future management options that have been recently considered by NORMAC. These include reductions of pool of the licensing units used in the NPF, (A-units, representing vessel length and engine power), gear restrictions as well as further seasonal and spatial closures. Although the operational implications of adopting some of these options have been the subject of NORMAC discussions, the scientific evaluation of options is not carried out in a structured framework but rather as individual assessments as different options are proposed by NORMAC. There is a need to establish a structured framework for management strategy evaluation so that the NPFAG and NORMAC can compare different options in a consistent way. This framework for management strategy evaluation should allow for the integration of risk analysis into the evaluation of management options. The consequences of each management strategy should be quantified and evaluated against the indicator of performance established by the NPFAG. The evaluation should include the estimation of the probability that, in the future, certain undesirable or desirable states of the stock are reached.

Predicting the response of megabenthos to the establishment of refuge/replenishment areas and acquiring an understanding of the ecological interactions between trawled and refuge areas are both essential steps in the effective design of refuges for fisheries habitat and the stocks they support. They are also necessary for the development of alternative fishing strategies that have less impact on habitat. To achieve these goals, it will be necessary first to obtain information on the recovery rates of habitat and then the processes which link trawled areas and refuges.

We propose to investigate the population dynamics (recruitment, growth, mortality, reproduction) of structurally dominant megabenthos habitat organisms and document the relationship between benthic habitat and ecological usage by important commercial finfish species. These issues — habitat dynamics and processes — have also been identified at FRDC workshops as high priority areas for future research. Also identified as high priority, especially by managers of tropical finfishes, is the need for finfish resource monitoring. To this end, we also propose to examine environmentally-friendly, fishery-independent techniques for measuring finfish abundance, including remote (baited) video stations and acoustics. Documentation of fish-megabenthos associations is the first step toward mapping the spatial distribution of snapper and emperor grounds on the basis of key habitat proxies, a process now underway in the development of an Interim Marine and Coastal Regionalisation of Australia.

Alternative fishing strategies which have less impact on habitat and lead to increased productivity among commercial species will, by preserving critical habitat in refuges, in turn help reduce conflict between commercial extractive activities and conservation. It will also improve the public perception of trawling. Two possible alternative strategies include: changing from fish-trawl to non-trawl methods; and changing trawling strategies to corridor trawling, in order to allow former trawling grounds to recover and resume their role as fisheries habitat supplying stock to the trawl corridors, whilst maintaining or even enhancing catch rates. In either case, the recovery time frames for the seabed habitat — and hence fisheries resources — are important, because they will influence the economic feasibility of switching to alternative fishing strategies.

The results of this study will become increasingly important as the requirement for ecologically sustainable fisheries management is implemented in trawl fisheries from the temperate zone to the tropics. The lessons learned from this study in the form of knowledge of habitat dynamics, and methods for monitoring habitats and commercial stocks will contribute to a rational balance between ecologically sustainable fishing, biodiversity and conservation when ESD related management changes are implemented in those Australian fisheries dependent on seabed habitat.

The eastern king prawn is the Australian east coast's single most valuable fish species. On the basis of previous experience and existing data, the risk of overfishing this stock is unquantified but appreciable. Obtaining data which can be used to advise fisheries managers on the necessity of intervention can only be obtained from a focussed, directed multi agency study.

In order to establish stock status, supply accurate advice and recommendations on management and monitor effectiveness of management intervention if need be, there are needs to develop procedures which;

(a) allow definition of the relationship between parent stock and recruitment levels in eastern king prawns, using fishery independent surveys as a means of determining recruitment levels.

(b) determine the status of the species and evaluate the potential risk of over-fishing.

(c) develop methods which can be used to evaluate the effectiveness of management intervention, if and when such intervention occurs.