Report of the Working Group on methods of fish stock assessments

The Working Group discussed in detail the working papers on the effects on assessments of age- dependent mortality and discards. It was apparent that, in both cases, there were discrepancies between the theoretical expectations of the effects of these factors on short- term forecasts and the results of practical tests using real data. The theoretical studies had also not covered all ramifications of interest. The Working Group decided to undertake further investigations of these aspects. The techniques required for the study of the effects of age- dependent natural mortality and of discards are very similar, both theoretically and practically, for both short- term and long- term assessments. It was, therefore, decided to organize both the investigative work and the report along these lines rather than on the basis of the topics distinguished in the terms of reference. The report of the work on short- term aspects is, therefore, in Section 2, and that on long-term aspects in Section 3.