Quick Definition
A wall of netting set vertically in the water in which fish become entangled by their gills as they try to swim through.
📖 Full Definition
Gillnets are flat panels of netting suspended vertically in the water column (either set on the bottom, drifting mid-water, or floating at the surface). Fish swimming into the net push their head through the mesh until the mesh catches behind their gill covers, entangling them. Mesh size determines the size of fish caught. Gillnets are highly selective for size but have major bycatch issues: marine mammals, sea turtles, and seabirds can drown in gillnets. Driftnet fishing in the high seas was banned by the UN General Assembly in 1991 due to its massive cetacean bycatch.
💡 Examples & Context
The vaquita porpoise (Phocoena sinus) is being driven to extinction by entanglement in totoaba (Totoaba macdonaldi) gillnets in the Gulf of California — fewer than 10 individuals remain.