Theoretical study of the influence of twine thickness on haddock selectivity in diamond mesh cod-ends

Using the cod-end simulation model PRESEMO, the influence of twine thickness on cod-end selectivity is investigated. The reduction of lateral mesh opening that arises as a result of both twine bending stiffness and the physical presence of the twine is considered. While it is shown that this leads to a reduction in cod-end selectivity with an increase of twine thickness, it does not fully explain the relationship found in the available experimental data.

The effect twine thickness may have on the ability of a fish to deform a mesh during the early part of a haul and how netting made of thicker twine may discourage a fish from making escape attempts is investigated. The influence that these factors may have is examined and when included in PRESEMO the resulting simulations are a much better representation of the experimental data.