Assessment of the physical characteristics and fishing performance of gillnets using biodegradable resin (PBS/PBAT and PBSAT) to reduce ghost fishing

Abstract Ghost fishing is caused by derelict synthetic‐fibre nets that have been lost at sea. Thus, biodegradable nets have been developed with the aim of protecting marine ecosystems. The performance of biodegradable nets and their ability to replace conventional gillnets was assessed. Two types of biodegradable nets were used in the experiment: one made from a blended resin containing 90 wt% polybutylene succinate (PBS) and 10 wt% polybutylene adipate‐co‐terephthalate (PBAT) (Bio‐1), and the other made from a polybutylene succinate co‐adipate‐co‐terephthalate (PBSAT) resin (Bio‐2) with improved flexibility and physical homogeneity. For No. 3 monofilaments (standard diameter, Ø, 0.284 mm), Bio‐1 and Bio‐2 both showed a wet straight‐line breaking strength of around 99% that of polyamide (PA). For No. 2 monofilaments (Ø 0.200 mm), the wet straight‐line breaking strengths of Bio‐1 and Bio‐2 were 84.9 and 93.0% that of PA, respectively, indicating worse physical properties for Bio‐1 at No. 2 thickness. The wet knotted breaking strengths of No. 3 thickness Bio‐1 and Bio‐2 were 92.9 and 82.7% that of PA, respectively. The straight‐line breaking strength of Bio‐2 was 1.1 times that of Bio‐1. The wet knotted breaking strengths of Bio‐1 and Bio‐2 were 80.2 and 93.4% that of PA, respectively, and the knotted breaking strength of Bio‐2 was around 1.2 times that of Bio‐1. Regarding flexibility, for No. 3 thickness monofilaments, the mean wet stiffness values of PA, Bio‐1, and Bio‐2 were 9.50, 15.23, and 9.68 g, respectively, indicating that Bio‐2 was similar to PA and around 1.6 times softer than Bio‐1. The fishing performance, by weight, was PA > Bio‐2 > Bio‐1; however, the difference between PA and Bio‐2 was not statistically significant. Biodegradable nets may not be a perfect solution, but we believe that they can contribute greatly to reducing ghost fishing and protecting marine ecosystems.