The objective of this study was to investigate the effect on
Mullus barbatus (red mullet) codend selectivity by increasing the codend
mesh size or reducing the number of meshes in the codend circumference. This
was performed through experimental sea trials and computer simulations. The
sea trials were carried out in the Adriatic Sea using a polyamide codend in
order to assess its selectivity, to record morphological (height, width and
length) and population size structure parameters of red mullet (Mullus
barbatus). The selectivity process in the codend was also simulated with an
individual-based model (PRESEMO) and a finite element model (FEMNET) to
calculate the codend shapes. By adjusting the behavioural description of red
mullet in the simulation, the model results reached an agreement with the
experimental results. Next these, behavioural parameters were used in the
simulation model to predict the effect of changing mesh size and number of
meshes around in new codend designs. The predicted effect and the benefit of
enforcing these designs on catch efficiency below and above minimum landing
size (MLS) were investigated. The results confirm that the reduction of
number of meshes in the codend circumference will be more beneficial than
increasing the mesh size.