Population structure, catch composition and CPUE of the artisanally harvested mangrove crabUcides cordatus(Ocypodidae) in the Caeté estuary, North Brazil: Indications for overfishing?

Abstract

-To evaluate the population structure of Ucides cordatus in the Caeté estuary, crabs were sampled bimonthly over 13 months in three Rhizophora mangle forest stands that differed in their accessibility and fishing history. Additionally, sex-and size composition of the commercial catch and catch per unit of effort (CPUE -the number of crabs captured per fisherman per day) were monitored between 1997 and 2003. Average and maximum crab sizes (carapace width, CW) from all three sampling sites combined were 6.1 cm and 8.8 cm in males, respectively, and 5.5 and 7.3 cm in females. Crabs were largest at the site that had been reportedly less exploited in the past. The overall sex ratio was skewed towards males (53−62%). Egg carrying females were only encountered during the rainy season. Mean crab abundance and biomass was 1.7 specimens m −2 and 142 g m −2 fresh mass. Only large males were commercially harvested (98% ≥ 6.5 cm CW). Their biomass was 53 g m −2 and the Caeté estuary yields an annual production of 1200 t of these large specimens. This is approximately the quantity that is currently being harvested. CPUE was similar in 1997 and 1998, then decreased by 15% until 2000 and stabilized for the rest of the study period. Mean capture size (cm CW) ranged between 7.2 ± 0.5 and 7.5 ± 0.2 and was above the size of 50% (and even 100%) male maturity and the legal minimum capture size. There is no evidence that the Caeté crab population is overfished, despite over 30 years of de facto open access exploitation. Apparently, the selectivity of fishermen and consumers for large male crabs as well as the local artisanal capture techniques are key factors in preventing an overfishing of the Caeté crab population until today. Our results suggest that the economic and social sustainability of this fishery will be affected well before the biological one, which should be considered in the recently proposed coastal co-management plan for the region. Key words:Mangrove crab / Ucides cordatus / Biomass / Sex ratio / Artisanal fisheries / CPUE / Management / Brazil Résumé -Structure de la population, composition des captures et CPUE du crabe de mangrove Ucides cordatus (Ocypodidae) capturé artisalement dans l'estuaire du Caeté, nord Brésil : signes de surexploitation ? Pour évaluer la structure de la population de Ucides cordatus dans l'estuaire du Caeté, ces crabes ont été échantillonnés tous les deux mois, sur une période de 13 mois, au niveau de trois sites de la mangrove à Rhizophora mangle qui diffèrent par leur accessibilité et leur historique de pêche. De plus, la composition (sexe et taille) des captures commerciales et celle par unité d'effort (CPUE -nombre de crabes capturés par pêcheur et par jour) ont été suivies entre 1997 et 2003. La taille moyenne et la taille maximale des crabes (largeur de la carapace, CW) de l'ensemble des 3 sites échantillonnés étaient de 6,1 et 8,8 cm pour les mâles, respectivement, et 5,5 et 7,3 cm pour les femelles. Les crabes étaient plus grands dans le site qui avait été moins exploité pa...

Salinity tolerance of northern Brazilian mangrove crab larvae, Ucides cordatus (Ocypodidae): Necessity for larval export?

“…In many regions of Brazil crabs are threatened by habitat destruction, diseases and fishery (Nordi, 1994;Botelho et al;2000, Alves et al, 2005Boeger et al, 2005). In our study area, 320 km southeast of the Amazon mouth, the local Ucides population is still comparably healthy (Glaser and Diele, 2004;Diele et al, 2005), but fishing pressure is increasing due to demographic growth and adequate management strategies are currently being discussed.…”

“…Approximately 140 km² of the Caeté peninsula is covered with mature mangrove forests densely populated by crabs, Ucides cordatus and fiddler crabs (Uca spp.) being the most abundant ones (Koch and Wolff, 2002;Diele et al, 2005;Koch et al, 2005). The region is characterized by semidiurnal macro tides with up to 5 m amplitude during the spring tide period.…”

Determinação da maturidade sexual de Ucides cordatus (Crustacea, Brachyura, Ucididae) em duas áreas de manguezal do litoral sul de Pernambuco, Brasil

“…Conhecido popularmente como caranguejouçá, pode atingir grande porte, sendo explorado em várias regiões brasileiras, onde serve como fonte de alimento e renda para populações ribeirinhas (RODRIGUES et al, 2000;PASSOS & DI BENEDITO, 2005;JANKOWSKY et al, 2006). Apesar de sua importância sócio-econômica, só recentemente tem-se notado um incremento das investigações sobre sua bioecologia (BRANCO, 1993;BOTELHO et al, 1999;IVO et al, 1999IVO et al, , 2000PINHEIRO & FISCARELLI, 2001;ALVES & NISHIDA, 2004;MONTEIRO & COELHO-FILHO, 2004;DIELE et al, 2005;PINHEIRO & HATTORI, 2006;ANDRADE et al, 2007;WUNDERLICH et al, 2008;ARAÚJO & CALADO, 2009), como também por aspectos sociais, econômicos, culturais e ecológicos relacionados a sua pesca (MANESCHY, 1993;NORDI, 1994;FISCARELLI & PINHEIRO, 2002;SOUTO, 2007). Com relação à determinação do tamanho da maturidade sexual que tenha levado em consideração tanto a maturidade morfológica como a fisiológica, somente um estudo foi desenvolvido por PINHEIRO & FISCARELLI (2001) até a presente data, mas para uma população do litoral de São Paulo.…”

Reproduction and management of the mangrove crab Ucides cordatus (Crustacea, Brachyura, Ucididae) at Iguape, São Paulo, Brazil

“…In the northeast (Diele et al 2005, Diele andKoch 2010) and southern (Dalabona and Silva 2005) regions of Brazil, the reproduction of the mangrove crab U. cordatus is closely associated with the rainy season, similar to that of other semi-terrestrial crabs (Crane 1943, Haley 1972, Henmi 1989, Henmi and Kaneto 1989, Debelius 1999. According to Nascimento (1993), U. cordatus migrates once a year, when the individuals leave their burrows and travel to the sea where they copulate and release their larvae.…”

“…Fiscarelli and Pinheiro (2002), working at Iguape, São Paulo, reported that U. cordatus performs two types of "andada": one for mating and the other for larval release. Diele et al (2005) and Góes et al (2000) mentioned that the "andada" of U. cordatus occurs on the first days of the full and new moon periods, in synchrony with the wider tidal amplitudes. Further details about the "andada" were recorded by Góes et al (2000), although they did not quantify this event or evaluate its dynamics or association with environmental factors.…”