The effect of gillnet twine thickness on catching efficiency and selectivity for common carp (Cyprinus carpio Linnaeus, 1758) fishery in Marmara Lake

The effects of multifilament gillnet twine thickness on selectivity and catching efficiency for the common carp fishery were investigated in this study. Sampling was carried out with multifilament gillnets of two different twine thicknesses (with 210d/2 and 210d/3) on 140, 150, 160, 180, 200 mm mesh sizes between June 2015 and December 2016 in Marmara Lake, located in Western Turkey. Higher modal lengths and lower catch per unit effort (CPUE) values and lower sub-minimum landing size (MLS) individuals rate (excluding 180 and 200 mm mesh sizes) were obtained in the thick multifilament material (210d/3) with the same mesh size compared to thin material (210d/2). All mesh sizes in both twine thickness provided modal lengths above the MLS. However, the thin twine material had a higher nominal percentage of undersized fish (8%), greater than the 5% accepted limit for total catches when all mesh sizes are considered together. As a result, the modal lengths and spread values increased and the selectivity and catching efficiency decreased with the thicker twine material.