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.