Comparison of fishing performance of biodegradable and nylon gillnets with different twine diameter

Abstract

Gillnets are usually made of nylon (PA) due to suitable material properties making them an efficient and commonly used fishing gear worldwide. However, considering that such gear is widely used and made of material that can endure long time of being exposed to marine environment, gillnets are often considered harmful if abandoned, lost or otherwise discarded. Such gear can cause marine plastic pollution and continue capturing marine animals over a long time (ghost-fishing). Efforts to develop new biodegradable materials to replace nylon in gillnets have been conducted. However, studies testing biodegradable gillnets have often shown reduced catch efficiency, challenging their acceptance in commercial fisheries. In this study, gillnets made of a new biodegradable PBSA material were assessed under commercial fishing conditions targeting cod (Gadus morhua) to compare their fishing performance with that of nylon nets. Two different monofilament netting diameters were tested. The results showed that relative catch efficiency between Ø 0.70 mm biodegradable and nylon nets was not significantly different (CRaverage = 107.0 % (CI: 86.2–132.1 %) and 80.58 % (CI: 15.23—155.76 %)). Increase in material diameter resulted in decrease of catches of cod of lengths 100–120 cm in biodegradable compared to nylon gillnets. This study showed that biodegradable gillnets can have a potential to reduce ghost fishing and plastic pollution at sea caused by this fishery and should be followed by further future long-term testing of material performance.