Combining fishers' perceptions, landings and an independent survey to evaluate trends in a swimming crab data-poor artisanal fishery

摘要

The fishery for the swimming crab Ovalipes trimaculatus in the southwestern Atlantic started in 2007, with an average catch of 64.36 ty(-1) during the period between 2008 and 2013. The fishery is under an open access regime and market demand exceeds the catch which raises concern about its future. It is also data-poor, which prevents researchers from using traditional assessment methods. The factors that limit the fishing effort were identified by analyzing the fishing operation, the decision making process of the fishers and CPUE. Changes in catch composition through space and time, and the distribution of the population along a depth gradient were also studied.Wind, recent yield and the price of crab were perceived by skippers as relevant factors when deciding to go fishing, but there was no relationship between these variables and monthly fishing effort. However, daily fishing effort depended on wind conditions. During the studied period (2008-2013) the CPUE of 2009 was the only one lower than the CPUE of 2008, and the number of fishing grounds as well as their respective area have not increased. The species depth distribution reaches 60 m deep, which is much deeper than the depths divers can reach (about 20 m), however the highest abundance of O. trimaculatus occurs at less than 30 m depth. The fishery did not show signs of depletion likely due to the combination of target species depth distribution and fleet characteristics limiting fishers' operability. This provides a unique opportunity to constrain fishing effort and avoid overcapacity, for example by banning larger vessels from the fishery.