Modelling the size selectivities of a trawl codend and an associated square mesh panel

Square mesh panels are often inserted in the codend or extension of a fishi ng net to allow under-sized fish an extra opportunity to escape. The effect iveness of the panel can be quantified by placing a small-mash cover over t he panel to catch all the fish that escape through it. This paper develops methodology for modelling the data From such covered panel experiments. The selection process is modelled in two stages: first. selection in the panel area, and second. conventional codend selection. Several different curves describing selection in the panel area are investigated. These include curv es that separate the process of fish "contacting" the panel from the select ion of the panel itself. Parameter estimation. inference, and methods for a ssessing goodness-of-fit are described. The methodology is illustrated usin g haddock and whiting data.