Marine Scotland Science has undertaken a number of detailed studies to assess the factors affecting the selectivity of gears used by the Scottish demersal fleet. Studies have been carried out to measure the effect on the selectivity of whitefish cod-ends by:
- Increasing mesh size
- Reducing the thickness of cod-end twines
- Removing lifting bags
- Shortening extension length
- Decreasing the number of circumferential meshes and incorporating square mesh panels or sorting grids
Similar selectivity investigations have been conducted on cod-ends used by the Nephrops fleet, topics covered include:
- Cod-end mesh size and shape
- Twine thickness, square mesh panel position and sorting grids