CCAMLR

As part of a wider research project aimed at developing management strategies based on the current toothfish assessment methodology using the Generalised Yield Model (GYM), a Java version of the GYM has been developed. The new version has been developed directly from the specifications kindly provided by Dr Andrew Constable. Some routines have been translated from the GYM FORTRAN code into Java. As such, if sufficiently similar results can be obtained from the JGYM and the current GYM given identical input, then this would be a major step towards a verification of the GYM. This paper, which will be given in the form of a Power Point presentation, will discuss how the JGYM was developed, indicate differences from the GYM where they exist, and compare results from the two programs with identical inputs.

This note describes the most recent additions to Fish Heaven and provides illustrative examples of its application as a tool for evaluating fisheries management systems. As in previous years there have been numerous small changes and additions to the functionality of the program. This note describes the large structural additions which have been made to Fish Heaven and which now allow a very wide range of models to be constructed and explored. The application of Fish Heaven as an evaluation tool is illustrated by some examples of how Catch Per Unit Effort performs as an indicator of abundance under simple stock scenarios.

The Generalised Yield Model (GYM) was first developed in 1995 as a generalised form of the Krill Yield Model, which was based on the method for evaluating yield developed by Beddington & Cooke (1983). The first version incorporated options for assessing long-term annual yield according to catches set by a proportion of an estimate of pre-exploitation biomass (as in krill), a specified catch in the units of biomass and relative to the recruitment parameters (as in toothfish) or according to a constant fishing mortality (F). It also included the capacity to evaluate yield per recruit. The latest version of GYM (Version 5.01b) differs from earlier versions in 2 main ways: (i) improved storage of output, population characteristics and presentation, and (ii) new features to allow specifying the starting biomass and/or age structure of the population obtained from surveys during a year. In addition, S-plus scripts have been developed to help with output diagnostics. The GYM User’s Manual, Specifications and Examples are also vastly improved. These features now provide the flexibility to undertake a wide range of assessments on stocks, not just specific to CCAMLR. In CCAMLR, the latest version of GYM can used on assessments for Antarctic krill, Patagonian toothfish, and mackerel icefish. This paper presents the specifications for the Generalised Yield Model Version 5, detailing the population model used in the projection program, the algorithm for evaluating yields and the requirements for inputting parameters into the model. It also details how different parts of the model can be manipulated to explore alternative functions. Finally, some examples are presented to show how the GYM can be validated by the user. The input and output files for these examples are available. The latest version of the Generalised Yield Model (GYM), Version 5.01b can be downloaded from the Australian Antarctic Division Website, www.aad.gov.au/marine_eco_software.