Not only that, but the gear alters the seafloor and poses a hazard to ships.
According to a report jointly produced by the UN Food and Agriculture Organization (FAO) and UN Environment Programme (UNEP), the problem is getting worse. Global fishing operations have increased in scale and reach, and fishing gear made of synthetic materials lives seemingly forever.
The study estimates that 10% of all marine litter consists of lost or abandoned fishing gear.
To be sure, most of the fishing gear is not deliberately abandoned. It is lost in storms or in "gear conflicts" that occur when fishing nets get entangled in bottom-traps. Whatever the reason, they continue to ensnare fish, a phenomenon known as "ghost fishing."
The problem must be addressed through "prevention, mitigation, and curative measures," says Ichiro Nomura, FAO Assistant Director-General for Fisheries and Aquaculture. The report makes several recommendations:
Financial incentives to encourage fishers to report lost gear or bring to port old and damaged gear.
Marks on fishing gear to help better understand the reasons for gear loss and identify appropriate preventive measures.
New technologies like reporting and retrieval systems, seabed imaging and GPS systems that aid in recovering lost fishing gear, and improvements in weather monitoring technology that can help skippers avoid deploying nets when dangerous weather is imminent.
New fishing materials that incorporate biodegradable elements.
Improved collection, disposal and recycling programs, like putting disposal bins on docks and providing boats with oversized, high-strength disposal bags for old fishing gear. According to the report, most ports do not have such facilities.
Better reporting of lost fishing gear. A key recommendation of the report is that vessels should be required to log fishing gear losses as a routine matter, without apportioning of blame.
Inventing "smarter" fishing gear. Examples include: Gear with passive acoustic pingers that remain active if gear is lost and can help prevent cetacean entanglement, nets incorporating pieces of cord that break when trapped animals begin to thrash, and magnets attached to fishing gear, which can deter sharks from approaching too closely.
(Photo: Loggerhead turtle entangled in pound net leader. Mike Tork, National Oceanic and Atmospheric Administration.)