The objective of the proposal is to examine all those factors affecting the selectivity of towed gears, other than simple diamond mesh size increases in the codend. These factors, such as square mesh windows in the trawl, if properly applied can be expected to reduce the total amount of unwanted by-catch entering the trawl or seine codend and thus make the selectivity in the codend more effective. The work will be based on a review of known but incomplete R&TD in these areas of work from EC and other national programmes. It will be confined to fisheries of the N.E. Atlantic Shelf.
Areas of research to be reviewed include :
- Codends completely in square mesh. Data exists in Scotland, England, Canada, Iceland and Norway.
- Square mesh panels in or in front of the codend. Comparative fishing experiments have been carried out in England, Scotland, Ireland, Denmark, Holland and Belgium within the last 5 years.
- Selector panels have been used to segregate species within the net thus subjecting one species to an escape opportunity but not the others.
- Metal grids in the codend or extension have been used successfully in Norway but there is no experience as yet in the EC.
- Bridle length, otterboard size and ground gear design can all modify fish behaviour in the catchment area of the trawl.
- Towing speed is believe to be a major factor in determining the species and size mix in the codend and this in turn will affect selectivity. Some limited work has been done in this area by the U.K.
