During trap-fishing investigations on the crab Cancer johngarthi along Baja California peninsula's southwestern coast, Baja California Sur, Mexico, conducted between 2002 and 2006, information was gathered to assess fishing efficiency in terms of the number of crabs caught per trap during one hour of operation (catch per unit of effort, CPUE = c/ht). As a result of vessel operation issues, some trap lines were abandoned, whereas vessels returned to land for repairing, and because the effective fishing time for these traps was significantly longer than normal, the information so obtained was regarded as reflecting the potential effect on fishing of traps lost during fishing operations (ghost fishing). Of 651 line sets analyzed, involving 45,152 traps, 77% had effective fishing times below 60 h, 14% between 70 and 150 h and 9% between 150 and 5,500 h. There is an exponential reduction in CPUE with increasing fishing time that could be associated to trap saturation. The number of crabs per trap also decreased with immersion time, fitting a power function. After 1,000 h of immersion, each trap may contain 7–18 crabs. Four hundred traps were lost over the course of 14 fishing trips. However, because the fishery is in the early development phases, the implementation of measures to avoid or restrain ghost fishing is deemed convenient.