Fishing time and trap ghost fishing for Cancer johngarthi along the Baja California peninsula's southwestern coast, Mexico.(Abstract)

ABSTRACT 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 rime, 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.

KEY WORDS: ghost fishing, traps, Cancer, crab, Mexico

INTRODUCTION

The effects of fishing methods on exploited populations are related to their design and mode of operation, which are based on the life-stage characteristics of both the target species and the environment in which it grows, and aim at selectively catching the largest amount of specimens of the target species meeting the size-related characteristics (Krouse 1989). There is a broad variety of fishing techniques (FAO 1964, Nedelec 1975, FAO 1978).

In the case of traps, selectivity will depend on mesh size, and trap fishing is regarded as causing a low environmental impact compared with the effects of trawling (Jennings & Kaiser 1998). However, one of the issues associated with the former is "ghost fishing", or unintentional catch because of the continuous operation of fishing traps/nets lost as a result of bad weather, loss of floats or fouling in the seabed. This issue is related to the capacity of lost fishing gear to catch specimens of either the target species or others related to it, as well as to the amount of fishing gear that gets lost and the time it remains undamaged.

The Code of Conduct for Responsible Fisheries (FAO 1995) acknowledges the impact of lost fishing gear and sets forth that governments should implement measures aimed at minimizing it. Ghost fishing may last many years, depending on the environmental conditions and the durability of fishing-gear materials; however, little is known on this issue, partly because of the difficulty involved in conducting long-term studies (Breen 1990). …

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