Status of the population structure of the mangrove crab Ucides cordatus (Decapoda: Ocypodidae) on the Piraquê-açu River estuary, Espírito Santo, Brazil

Abstract

The land crab Ucides cordatus is a keystone species of neotropical mangrove forests and an important resource of the artisanal fisheries. The spatial and temporal distribution of U. cordatus in the mangrove area of the Piraquê-açu river estuary was determined following a longitudinal estuarine salinity gradient (lower, middle, upper estuary) and along the vertical intertidal gradient. The numbers of open and closed burrows were counted monthly on fixed transects, the inhabiting crabs were caught, sexed and the carapace width measured, during 1 year. The mean crab density was 2.5 ind.m-². The highest crab density (3.9 ind.m-²), linked to high numbers of juvenile crabs, was found on the upper estuary and correlated with lower salinities. High intertidal levels had higher crab densities than lower intertidal levels, except in the upper estuary. Males were smaller than females; the mean carapace width of the population was 4.89 cm, below the minimum legal harvesting size (6 cm). The predominance of females over males at some sites (especially close to villages) brought out the advanced level of overfishing of this U. cordatus population and highlights the urgent need of management actions.<br>O caranguejo Ucides cordatus é uma espécie chave nos manguezais da região neotropical e um importante recurso pesqueiro para populações tradicionais. A distribuição espacial e temporal de U. cordatus no manguezal do Rio Piraquê-açu foi estudada ao longo de um gradiente de salinidade, no estuário inferior, médio e superior na faixa entre-marés. Mensalmente durante um ano. O número de tocas abertas e fechadas ao longo de transectos fixos, foi contado mensalmente, ao longo de um ano, e os caranguejos capturados foram sexados e medidos quanto à largura da carapaça, sendo posteriormente liberados. A densidade média de caranguejos foi de 2,5 ind.m-². A maior densidade (3,9 ind.m-²), juntamente com o maior número de jovens, foi encontrada na parte superior do estuário, correlacionada com baixas salinidades. Nos níveis mais altos de maré a densidade de caranguejos sempre foi alta, exceto na região superior do estuário. Os machos foram menores do que as fêmeas; o tamanho médio da carapaça da população total foi de 4,89 cm, abaixo do tamanho legal permitido para captura (6 cm). A predominância de fêmeas sobre machos em alguns pontos, principalmente próximos às vilas, revela o avançado nível de sobreexplotação da população de U. cordatus, evidenciando a necessidade urgente de ações fiscalizadoras

A pesca nos manguezais no Estuário do Rio São Francisco: uma abordagem sócio-ecológica com ênfase no caranguejo Ucides cordatus (Linnaeus, 1763)

“…The present study also recorded similar founds to Conti et al (2010), since in the site 6 was recorded the highest frequency of small crabs (juvenile) at high density (Table 1, Figure 4).…”

“…In this type of habitat, large crabs apparently exclude smaller ones from preferred habitats , thus favoring the dominance of the largest crabs. Conti et al (2010) found that highest crab density is linked to high numbers of juvenile crabs, which was found on the upper estuary and correlated with lower salinities .…”

“…al., 2004), and the fishery of U. cordatus by the local communities is very high (Santos et al not published), these two factors can also contribute to the lower densities recorded in the present study. Moreover, in general, recent papers have registered smaller crab densities than the older studies, probably revealing that the crab population has been overfished, mainly due to unsustainable practices (Conti et al, 2010).…”

“…Additionally, it is remarkable that the U. cordatus density can vary between different mangrove areas as a result of their degradation or as a result of a higher incidence of this extractive feature , as well as due to intrinsic factors of a particular mangrove forest (primary productivity, patterns of larval recruitment, among others) (Conti et al, 2010). Since in the study area shrimp farming is the main impact causing deforestation of mangroves (Santos et.…”

Biología poblacional del cangrejo de manglar <i>Ucides cordatus</i> (Decapoda: Ucididae) en un estuario tropical semiárido

“…Male-biased selectivity in exploited species such as U. cordatus can also change the sex ratio (Fenberg & Roy, 2007). According to Diele et al (2005), areas with a longer history of exploitation have a higher proportion of females, and this deviation may indicate that the population has been overfished (Conti & Nalesso, 2010;Sforza et al, 2010). The results obtained here suggest no evidence of overexploitation.…”