Gillnets are long rectangular nets which are set horizontally along the ocean floor.
How gillnets work
Gillnets are long rectangular panels of netting with diamond-shaped mesh that are held vertically in the water column and anchored to the ocean floor at either end.
Fish swim into the net and are entangled by the gills, fins and spines. The nets are kept vertical by the floats along the top and weights along the bottom.
Only demersal gillnets (touching the ocean’s floor) are permitted in Commonwealth fisheries, and are used by one Commonwealth fishery to catch school and gummy sharks.
Gillnets are normally used in shelf waters less than 100m deep.
Environmental impacts and management
Gillnets have a minimal impact on the substrate as they are static when set. Gillnets have the potential to interact with marine mammals, although when set properly, larger predatory sharks and marine mammals will bounce off the tight mesh. Refer to AFMA’s Australian Sea Lion Management Strategy and Dolphin Strategy.
Gillnet mesh size is regulated by AFMA so that mostly medium size gummy shark are caught. The undersize sharks are able to swim through the mesh and larger sharks bounce off the net. This leaves both smaller sharks which haven’t had the chance to reproduce and large breeding sharks in the water.