Ghost fishing is the term used to describe the continued capture of fish and other living organisms after a fisherman has lost all control over the gear. Traps may be lost for a variety of reasons including theft, vandalism, abandonment, interactions with other gear, fouling on the bottom (i.e., traps and ropes are caught on rocky substrate), bad weather, and human error (Laist, 1995). Annual trap loss can be as high as 20% to 50% of fished traps in some fisheries (Al-Masroori et al., 2004). Because lost traps can continue to fish for long periods, albeit with decreasing efficiency over time (e.g., Smolowitz, 1978; Breen, 1987, 1990; Guillory, 1993), ghost fishing is a concern in fisheries worldwide. Few studies on the ghost fishing of lost traps have been carried out in European waters, and there has been no information from southern European waters. Ghost fishing of parlour pots used to catch lobsters and crabs off the south-west coast of the United Kingdom was studied by Bullimore et al. (2001), and Godøy et al. (2003) carried out an experimental study on much larger, deliberately lost pots for red king crab (Paralithodes camtschaticus) in Norwegian waters. In both cases the effect of ghost fishing by parlour pots was deemed to be relatively small compared to the effects of other types of traps used in Canadian and American fisheries (Brown and Macfadyen, 2007). In southern Portugal, pots and traps of various types are among the most widely used gears in the small-scale fisheries. Fishing vessels <9 m (local category) can legally fish up to 500 traps, and coastal category vessels (9–12 m and >12 m in total length) are allowed up to 750 and 1000 traps, respectively. The most widely used traps in the Algarve are 1) metal frame, hard plastic netting, single entry traps for octopus (covo), 2) large, metal frame traps for catching cuttlefish and fish (armadilha), and 3) wire traps (murejona) for catching fish. However, only the covo traps and murejona traps were used in our study. Under the Common Fisheries Policy and the European Community directive on habitats and species, member states are responsible for local fisheries and are obliged to take measures to minimize or mitigate the negative effects of fishing activity. Concern over the effects of lost gear in European waters has led the European Commission to finance two pan-European projects on ghost fishing. The first project focused only on gill nets and trammel nets (Erzini et al., 1997), and the second project included studies on lost traps in several European areas (Godøy et al., 2003). Here we report the results from one of the studies carried out with two types of traps in the northeast Atlantic (South coast of Portugal). The catches of deliberately lost traps were monitored and estimates of the number of trap losses and causes of trap losses were obtained through surveys of commercial fishermen.