Reports of the ad hoc Working Group on the use of effort data in assessments and the Working Group on methods of fish stock assessments

This issue contains the Reports of two ICES Working Groups, chaired by Dr J.G. Shepherd, United Kingdom, which were established to examine important aspects of the methodology used in the assessment of fishery resources and the provision of scientific information and advice on their conservation and management. The first Report, presented in Part I, is concerned with an evaluation of the use of fishing effort data in assessments, with special reference to the determination of fishing mortality levels; the second Report, presented in Part II,

extends these considerations and also deals with other

met~odological problems, including the application of the

separable VPA method and the evaluation of factors which

may invalidate yield-per-recruit calculations and the derivation of biological reference points.