CCAMLR

This paper presents, for consideration by the Commission, the projected outcome of the budget for 2004, a draft of the 2005 budget and an indicative forecast for 2006, presented in a format determined by the Commission at its 2002 Meeting. The budgeted expenditure for 2004 is not expected to be exceeded, and possible savings of Scientific Committee-related expenditure have been identified. After accounting for the effect of Staff Assessment Levy, this could yield A$7 500 which, when added to the surplus brought forward from 2003, generates a 2004 surplus of A$39 200 to be recorded as income in 2005. The availability of a surplus enables additional travel expenditure in 2005 to be incurred without an increase in Members’ contributions but, as envisaged by the Commission last year, such an increase in contributions will be needed to pay for the full Implementation of the C-VMS. There is no overall increase in the 2005 budget anticipated in respect of reallocating the Commission’s Headquarters.

A short simulation study has been carried out to investigate the size of the bias in estimates of growth parameters resulting from fish of different sizes having different probabilities of being included in catch samples. Fish were included in catch samples from the population with probability equal to an assumed relative selectivity at length. Both the mean growth parameters and the selectivity function used in the simulations closely matched those used for current toothfish assessments in Subarea 48.3. Substantial selectivity-induced bias was demonstrated, with the simulated catch sample data producing considerably lower estimates of L? and higher estimates of K than in the true population. The simulated catch sample data and the growth parameter estimates were similar to those reported by Belchier (2004, WG-FSA- 04/86). This suggests that the growth parameters used in the current toothfish assessments in Subarea 48.3 are not incompatible with the Belchier (2004, WG-FSA-04/86) data.

The ASPM model used by Agnew and Kirkwood (2004, WG-FSA-04/82) has been modified through the introduction of a new annual selectivity function, modelled as a unimodal, algebraically decaying function of age, with three easily interpretable parameters.
When only a single selectivity curve was fitted for all years, the change to the new selectivity function improved the fit to length frequency data achieved last year, but the fit was still poor. The fit to the CPUE was also poor.
With selectivity parameters allowed to be estimated on an annual basis the fits are substantially improved. However, by allowing all parameters to be estimated in this way the model is over-parameterised and regularly reaches preset parameter boundaries. With one or two parameters of the selectivity estimated only once the fit to length frequencies is good but infinite populations are estimated. If the CPUE data are given high weight in the fitting, then the model has sufficient flexibility to change the selectivity to fit the CPUE very closely. Convergence problems were noted for the highly parameterised versions of this model.
Revisions to the selectivity model this year have led to an ASPM with superior performance. However, this study demonstrates that the ASPM is still not suitable for use when assessing South Georgia toothfish populations by fitting to the available catch length frequency data and CPUE data.

We investigate the spatial and temporal (i.e. fishing season) variation both systematic and random in haul-by-haul catch and effort data from the longline fishery for Dissostichus eleginoides in Subarea 48.3. We concentrate on presenting the results of preliminary work on the potential effects of changing fishing patterns on the standardisation of the CPUE time series. We consider whether the spatial pattern of fishing might have changed over the years, whether the current measure of fishing effort (number of hooks on a line) has changed in its fishing properties over time, and if soak time is a useful additional measure of effort. We then consider how these results might impact on the assessments, particularly the standardisation of the CPUE series. The results indicate that fishing for Dissostichus eleginoides is not uniformly distributed in its range. In some years, though not all, the fishery becomes concentrated into distinct grounds. In the CPUE standardisation procedure we found that although soak time was a significant predictor of catch the fitted relationship was not consistent with using soak time as a co-measure of effort by expressing CPUE as kg per hook-hour. In contrast the fitted log-linear relationship between catch and number of hooks set was consistent with using this variable directly as the measure of effort. The analysis of the interaction between the fishing season and the fitted coefficient for log(Hooks Set) in the regression model for catch suggested a declining trend in the coefficient over time. This may indicate that catchability has been changing and has perhaps become greater over time as a result of effort concentrating in productive locations. We recommend further consideration of the spatial characteristics of the fishery and its implications for using CPUE as an indicator of abundance.

This paper describes a possible method for implementing the precautionary approach in assessments of Dissostichus stocks when a number of different datasets are being integrated for estimating current biomass and age structure. Consideration is given to its application to the assessment of Dissostichus eleginoides in Division 58.5.2. CASAL and GYM are key elements in the implementation described in this paper but the methodology is laid out in such a way that alternative software solutions could be used in either or both of their places. The framework for this procedure has four main components. The first is the integrated assessment, undertaken external to the GYM by software such as CASAL. The second step is the sampling of the “current state” and associated parameters to provide inputs to the GYM. The third step is to use the GYM to undertake a number of projection trials, determining the median pre-exploitation spawning biomass and future states of the stock under the nominated harvest strategy. The fourth step is to test the performance of the harvest strategy against the decision rules. A controller is proposed to be used to manage the entire process including calling the CASAL or other software, the GYM and for evaluating the harvest strategy. The structure of this approach will help explore the value of integrating the datasets for Dissostichus elegionoides assessments such as are available for Division 58.5.2, which include recruitment surveys, commercial catch data from trawl and longline activities (biomass, length composition and age), and mark-recapture data. This method is an extension of current practice, although the framework is newly described and better coordinates the integration of the different steps in the precautionary approach used by WG-FSA. It is recommended that this approach be implemented for use by WG-FSA at its next meeting.

Three Operating Models (OMs) reflecting an optimistic, an intermediate, and a pessimistic current status for the toothfish resource in the Prince Edward Islands are developed. These are planned for use for initial trials of candidate Management Procedures (MPs) to provide future TAC recommendations for this resource. These will aim to provide an appropriate balance between avoiding risk of severe depletion and utilising potential harvest from the resource, in circumstances where the resource status is very uncertain.

A version of the confidence interval calculating program TrawlCI was recompiled to enable it to be run within the DOS emulator of recent versions of the Microsoft Windows operating system. The performance of the recompiled version was compared with that of the original version.
The recompiled version of TrawlCI produced very similar, though not identical, results to the original version. We attribute this to differences in the minimisation routines of the recompiled version. We conclude that the differences evident from these tests are unlikely to significantly influence the estimated long-term yield of Dissostichus eleginoides or Champsocephalus gunnari