Effect of marine debris on the catching ability of bottom gill net

Abstract

Changes in internal and external factors during operation of bottom gill net will affect to catch ability of bottom gill net. The presence of marine debris in the ocean is predicted to influence the internal factors of gill nets which leads to reduction of catch ability. This study aimed to identify the factors that lead to decreasing of catch ability of bottom gill nets and to calculate the reduction of catch ability due to changes in hanging ratio caused by marine debris. Fishing activity using bottom gill net for 10 replications was conducted to identify the factors that affect the bottom gill net's catch ability, while the reduced catch ability is calculated through the percentage of net area covered by garbage, changes in the hanging ratio and tension of the net body due to the entangled and twisted garbage in the net. The results showed that there were three factors that led to a reduction in the catch ability of bottom gill nets due to marine debris, namely: garbage stuck to the body of the net, trash entangled in net webs and trash wrapped around the body of the net. The closure of the mesh, changes in openings of mesh and net tension result in a decrease in the catch ability of bottom gill nets by 20-50%.