The effect of yarn thickness on catching efficiency and length selectivity in monofilament gillnet

In this study, the effect of yarn thickness on catch efficiency and length selectivity in monofilament gillnets was investigated. Field studies were carried out in Seyhan Dam Lake between September-2020 and September-2021, with 26, 28, 30 and 32mm mesh sizes and different yarn thicknesses (1=26mm 0.16mm, 2=26mm 0.18mm, 3=28mm 0.16mm, 4 =28mm 0.20mm, 5=30mm 0.16mm, 6=30mm 0.20mm, 7=30mm 0.33mm, 8=32mm 0.16mm, 9=32mm 0.20mm) were made using 9 post gillnets. A total of 34 experimental hunting operations were carried out. As a result of the operations, 1260 Sander lucioperca and 904 Rutulis sp. has been caught. The results showed that the yarn thickness affects the catch efficiency in some mesh sizes, but it does not affect the catch efficiency in some mesh sizes. This is due to the fact that the yarn thickness of the net is a parameter that also affects the wear. According to the Kolmogorov Smirnov test results, the length distributions obtained from different yarn thicknesses showed that it was not statistically significant. The SELECT method was used to determine the selectivity parameters for Sander luciopera. Low model deviation was obtained with Normal-scale for both 0.16 mm thread thickness 26, 28, 30 and 32mm mesh nets and 0.20 mm thread thickness 28, 30 and 32mm mesh nets. With the help of this model, it has been seen that the optimum catch lengths determined for different yarn thicknesses are very close. All these results showed that yarn thickness had no effect on length distribution and length selectivity, but could affect catch efficieny.