Estimating the size-selection curves of towed gears, traps, nets and hooks

A general statistical methodology for analysis of selectivity data from any type of fishing gear is presented. This formal statistical modelling of se lectivity is built on explicit definitions of the selection process and spe cification of underlying assumptions and limitations, and this gives the re sulting estimates of gear selectivity (and possibly fishing power) a clear interpretation. Application of the methodology to studies using subsampled catch data and to towed gears having windows or grids is outlined, and exam ples applied to passive nets and towed gears are presented. The analysis of data from replicate deployments is covered in detail, with particular rega rd to modelling the fixed and random effects of between-haul variation. Rec ent developments on the design of selectivity experiments are introduced an d demonstrated.