Fish traps are an example of passive fishing equipment and can be used to catch various types of fish, crustaceans and molluscs; they consist of cages which the prey is encouraged to enter by a bait. Once in, the animal then finds it impossible to get out. A large number of traps (up to one hundred) are laid on the seabed and linked together with a long cable. They are weighted so as to remain on the bottom and easily seen little buoys mark their position on the surface. Trap fishing is quite selective, with a very low by-catch. However, if a trap should break loose underwater it becomes a rogue trap, representing a considerable danger for benthic species that can remain trapped inside for good. There are many types of trap, each designed to catch a specific prey: cuttlefish, fish and matis shrimp, in particular.