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.