A fish trap is a trap used for fishing. Fish traps can have the form of a fishing weir or a lobster trap. Some fishing nets are also called fish traps, for example fyke nets.
A typical contemporary trap consists of a frame of thick steel wire in the shape of a heart, with chicken wire stretched around it. The mesh wraps around the frame and then tapers into the inside of the trap. When a fish swims inside through this opening, it cannot get out, as the chicken wire opening bends back into its original narrowness. Contemporary eel traps come in many shapes and sizes and are constructed of many materials. In earlier times, traps were constructed of wood and fibre.
Fish traps are used to catch finfish species that live on or near the sea floor, normally on seamount and continental slope waters of between 300 and 700m deep.
How traps work
Fish traps are weighted at the bottom so when set, they land on the sea floor the correct way up. Traps are baited so fish will be attracted to the scent of the bait and swim through the entrance. The traps are designed in a way so that fish cannot escape once inside the trap. Fish traps have escape gaps of a minimum size to ensure that juvenile and non-target fish are able to escape.
When set, traps are connected to a downline which is bridled at the end and attached to the trap at opposite ends. The downline is connected to a buoy on the surface which allows fishers to locate the traps. Traps used in AFMA managed fisheries are only permitted to have one entrance, as well as must meeting other minimum requirements relating to the size of the trap and escape gaps.
Environmental impacts and management
Fish traps have a minimal impact on the marine environment, with low levels of bycatch and interactions with protected species being rare. Fish which have been caught in traps are often alive and in good health when they reach the surface, which greatly increases post capture survivability.
Traps can become snagged on the bottom and get broken off, although this is not a common occurrence. For this reason, in the Coral Sea Fishery traps must be fitted with sacrificial anodes to allow trap doors to open once the anode disintegrates.