Abstract
An application of environmentally degradable plastics for fishing nets may help solve the ghost fishing problem. In this study, biodegradation of aliphatic polyester, poly (ε-caprolac tone) (PCL) was studied in deep seawater under a low temperature of 0.6°C during the period of 8 months at atmospheric surface pressure. Processes of biodegradation were analyzed by monitoring the time-dependent changes in mechanical strength and scanning electron micrographs (SEM) of the surface of PCL monofilaments. The strength of 110 D fibers decreased to about 80 % of initial value after one month of soaking, about 60 % after three months and about 35 % after six months. After eight months of soaking, the filament did not keep its original shape and the strength reached zero. Thus it could not be subjected for the strength measurement any further. From SEM micrographs of PCL monofilament fibers soaked in deep seawater for 3 and 8 months, pinholes were observed on the surface of treated fibers. The number of these pinholes increased with the soaking period. This phenomenon strongly suggested that the degradation of PCL in deep seawater is caused at least partly by microbial degradation. From these results, the application of biodegradable plastics such as PCL for fishing gears is suggested to be effective in reducing ghost fishing problem caused by non-biodegradable fishing nets.
