It is unknown whether the current apparent failure of the stocks to recover in the NP Tiger fishery is related to limited management options, serial depletion of stocks or to the use of the now somewhat discredited MSY and EMSY management targets (see, for example, Larkin, 1977 and summaries in Pitcher & Hart, 1982).

In two recently completed FRDC projects (FRDC 95/014 and 98/109), a preliminary attempt at stock-based assessments was undertaken. These show that some stocks are much more depleted than the single-stock model would suggest. There is a need to clarify which areas are most affected and why these are performing so poorly. There is also a need to develop a multi-stock operating model to open a new direction for modelling in the NPF. This technically complex model would have the potential to benefit the management of benthic crustacean species worldwide. (It should be noted that no operating model, particularly not a spatially explicit one, has been developed for any prawn fisheries in Australia.)

In species, such as prawns, whose dynamics are dominated by yearly recruitment variation, the MSY may well give a false expectation of stability. Management targets that relate to present conditions rather than to equilibrium conditions (e.g. a target fishing mortality rate) may better serve intrinsically variable fisheries, such as prawns. However, reference points developed worldwide have concentrated on output controlled management systems. Given AFMA’s requirement to satisfy its ESD objective, there is therefore a need to consider uncertainty explicitly and to identify performance indicators and harvest strategies that are as robust as possible to incorrect assumptions and estimation errors deriving from limited data. Most importantly, these should be developed in the context of spatially explicit stock assessment models and an input controlled management system.

An international review of the NPF tiger prawn assessment agreed with the conclusions of the 2001 assessment that tiger prawn stock levels were critically low, especially for brown tiger prawns. The 2002 assessment further concluded that brown tiger prawn levels were too low and also emphasized the critical need for an independent monitoring program given the confounding and complexities of the catch rate data used as the sole index of abundance in the NPF assessments. The 2003 assessment suggests that brown tiger prawn stocks are recovering but, given the high level of uncertainty in the assessment, this recovery needs to be independently tested.

The survey data used to determine the initial design for this project (see Background) was more than a decade old and did not cover the full study area. Since the first survey, changes have been made to the survey design to improve the accuracy of the abundance estimates obtained from the surveys. This design needs to be further developed and tested. Work has also begun on developing methods for incorporating the results of the surveys into stock assessments, but more research is required to overcome several technical difficulties encountered.

In this proposal, the CSIRO salaries associated with testing the survey design and with developing new methods of incorporating the results into stock assessments are seen as research. We are therefore requesting about $47,000 from FRDC’s MOU funds. For this reason, CSIRO is also supporting the project to the scale of about $86,000. The remainder of the project, some $520,000, will be underwritten by the industry as agreed in NORMAC, June 2003. The industry and NORMAC have also re-affirmed the long-term need for regular industry-funded monitoring surveys based on the output of this project.

There is a need to provide an updated design for the NPF that would work in the long-term to provide indices of abundance for key species and enhance a difficult-to-use commercial catch rate series. Furthermore, this design needs to address target, byproduct and possibly some effects-of-trawling issues to make the best use of the surveys.

An international review of the NPF tiger prawn assessment agreed with the conclusions of the 2001 assessment that tiger prawn levels are critically low, especially for brown tiger prawns. The 2002 assessment has further concluded that brown tiger prawn levels are too low but has also emphasized the critical need for an independent monitoring program given the confounding and complexities of the catch rate data used as the sole index of abundance in the NPF assessments.

The survey data used to determine the initial design for this project (see Background) is more than a decade old and does not cover the full study area. Therefore the initial surveys will be largely exploratory in nature and very much a trial to see if the proposed design is effective. Also, the survey design includes integrated components such as the assessment of long-term changes in fishing power and the contraction of the fishery over time that have not been undertaken in prawn survey designs (both nationally and internationally) before. These aspects highlight that this project has a large research component; the appropriate survey design is still being developed and methods for incorporating the results of the surveys into future stock assessments need to be developed.

In this proposal, the CSIRO salaries associated with modifying the survey design and with developing new methods of incorporating the results into stock assessments are seen as research. We are therefore requesting about $60,000 from FRDC’s MOU funds. For this reason, CSIRO is also supporting the project to the scale of about $87,000. The remainder of the project, some $510,000, will be underwriten by the industry as agreed in NORMAC, June 2003. The industry and NORMAC have also re-affirmed the long-term need for regular industry-funded monitoring surveys based on the output of this project.

There is a need to provide an updated design for the NPF that would work in the long-term to provide indices of abundance to key species and enhance a difficult-to-use commercial catch rate series. Furthermore, this design needs to address target, byproduct and possibly some effects-of-trawling issues to make the best use of the surveys, as they will be a large expense to the industry.

The Queensland East Coast Trawl Fishery Management Plan, was completed and introduced on 21st December, 2000, with the Management Plan’s Regulatory Impact Statement released October 2000. The plan sets performance criteria for a 40% reduction in bycatch and a 25% reduction in damage to benthos. Environment Australia also sets criteria on the sustainability of (1) target species, (2) retained bycatch (by-product), and (3) discarded bycatch species from trawl fisheries; a key factor of which is the total mortality on these species caused by the fishing operation. FRDC are currently funding QDPI research (FRDC#2000/170) to describe and quantify trawl bycatch in Queensland and the preliminary effects of bycatch reduction devices (BRDs) on the bycatch.

“Hoppers” are product-quality and cost-efficiency enhancement devices that are being progressively introduced into the South Australian, Western Australian, and Northern Prawn Fishery, and have been fitted by a small number of trawlers on the Queensland East Coast. These devices are recommended in the 1997 QCFO (QSIA) sponsored ISO Best Practice manual for onboard handling of prawn catch. Anecdotal reports suggest that these devices not only enhance product quality but significantly increase the survival of bycatch species that are caught by the trawl net (despite BRD’s), because the catch is dropped into a tank of fresh sea-water rather than onto a dry sorting-tray.

Therefore there is a need to pro-actively evaluate and document the effect of Hoppers on survival of discarded bycatch to ensure that the Queensland Prawn Trawl fleet gains maximum recognition for the “environmental credits” accrued as Hoppers are progressively introduced. This would provide an added bonus to a process already underway as a commercial evolution in trawl fisheries around Australia. Such information could also act as an environmental incentive, apart from the product quality and cost consideration, for trawler operators to fit Hoppers.

There is a particular need in the case of the smaller inshore boats involved in the Queensland East Coast banana fishery. Here there is considerable community pressure for inshore closures to cover local and tourist destination beaches, in response to discarded bycatch washing up after trawling operations. Appropriately sized non-mechanised Hoppers are currently under development but these will need to be independently evaluated to ensure that the community is satisfied that they will reduce bycatch mortality, ie no dead fish on politically sensitive beaches.