Artisanal Fishery of the Mangrove Crab Ucides cordatus (Ucididae) and First Steps Toward a Successful Co-Management in Bragança, North Brazil

Abstract

The Bragança district in north Brazil offers a unique opportunity for examining the functioning of a small-scale mangrove crab fishery. North Brazilian mangroves are extensive and the large crab Ucides cordatus is very abundant, even though this slow-growing species has been exploited for decades all year round. Ucides sustains a considerable annual yield of ∼7 tons per km² in this district, and 42% of the rural coastal households are involved in the collection or commercialisation of this crab. We describe capture techniques and main outcomes of 8 years of participatory fisheries monitoring, evaluate the status of the U. cordatus population and characterize the commercialisation of the crabs. The average number of crab collectors working on Bragança peninsula each day was 121 ± 105 (<1 man-day per km² per day; data source 2003). In 2003, their net income was 1.5- to 2.5-fold higher (US$ 122–196) than the national minimum wage in that year (US$ 80), but still insufficient given an average household size of five people. Mean carapace width of the catch between 1998 and 2005 differed at the most by 2.5 mm, without showing a particular trend. The total crab population of Bragança peninsula was estimated at ∼231 million specimens and fisheries landings were 22% below the calculated annual maximum sustainable yield (1,044,881 crabs). The latter fact is considered important for reducing the risk of a sudden non-linear down-fishing of the economically valuable upper size classes in this slow-growing species, in which the first negative effects of the fishery may remain masked for some time. Further key factors which have prevented rapid overfishing until today include conservative capture techniques that prevent blanket-coverage exploitation, the current size (and sex) selectivity by fishermen and consumers and the integrity and connectivity of the mangrove habitat. At the request of local user communities, the area was declared an “Extractive Marine Reserve” (RESEX) in 2005, a relatively new management approach in coastal Brazil, crucially depending on direct involvement of resource users. The presence of researchers in the study area and participation of locals in our crab fisheries monitoring had positively influenced confidence and decision-making capacities of the latter, making Bragança district an ideal site for RESEX. Registration of resource users and legislation must now be improved for the successful implementation of a co-management plan for sustainable use.