Dimensionamento e sobreposição de nichos dos portunídeos (Decapoda, Brachyura), na Enseada da Fortaleza, Ubatuba, São Paulo, Brasil

Abstract

ABSTRACT. BREADTH AND OVERLAP NICHES OF THE PORTUNID CRABS (DECAPODA , BRACHYURA), lN FORTALEZA BAY, UBATUBA, SÃO PAULO, BRAZIL. The niche breadth ofthe Portunidae and their overlap on the subtidal sediments ofFortaleza bay, Ubatuba (São Paulo) was analyzed. Samples were made monthly from November/ 1988 to October/1989, in seven areas ofthe bay using a shrimp fishery boat equipped with two otter-trawls. Each area was characterized based on environmental factors such as depth, temperature, salinity, dissolved oxygen, organic matter and granulometric composition ofthe sediment. The number ofindividuals of each species was registered to each area (resource). Levins's standardized measure (BA) and niche percentage were calculated. Five species of swimming crabs were recorded in this study: Ca/linecles ornalus Ordway, 1863, Arenaeus cribrarius (Lamarck, 1818), Porlunus spinimanus Latreille, 1819, Ca/linecles danae Smith, 1869 and Porlunus spinicarpus (Stimpson, 1871). The widest ecological niche occurred to C. ornalus, present in ali sampled areas (generalist species). Such fact can be related to high sediment tolerance when it is compared to P. spinimanus (especialist species) which was limited to the areas with coarse granulometric fractions. Highest niche overlap was verified between C. danae and A. cribrarius may be due to greater salinity tolerance of these species. The low occurrence of P. spinicarpus and its reduced niche size in Fortaleza Bay are due to association of this species to cold water currents (ACAS) more evidente in smaler depths during summer months. One future evaluation of the portunid diet can be use fuI to complement informations about this important aspect of the marine ecology. KEY WORDS . Portunidae, distribution, niche, sediment, swimming crab A área ocupada por determinado organismo na natureza é reflexo da atuação isolada ou conjunta de fatores extrínsecos, sejam eles ambientais ou bióticos. Com relação à fauna bentônica marinha, têm-se verificado que os fatores ambientais mostram maior influência nos padrões de distribuição quando comparados com os bióticos (FORNERIS 1969).

ON THE POPULATION STRUCTURE OF Callinectes danae AND Callinectes ornatus (DECAPODA, PORTUNIDAE), IN GUANABARA BAY, RIO DE JANEIRO STATE, BRAZIL

“…In agreement with the present study, the highest abundance of C. ornatus was also observed by Negreiros-Fransozo & Fransozo (1995), Pinheiro et al (1997), Reigada & Negreiros-Fransozo (2001) in Ubatuba (SP) and by Lavrado et al (2000) and Carvalho-Cunha (2003) in Guanabara Bay. According to Pinheiro et al (1997) in their work in Ubatuba, C. omatus presented a wide ecological niche which overlapped that of other species of portunids, thus being considered a generalist species.…”

“…Another possible hypothesis is the spatial stratification between sexes, with males preferentially occupying environments more easily sampled by trawl net, as this was the instrument used in the capture of the specimens in all the studies cited. The stratified behavior regarding sex and individual size for C. ornatus was verified by Pita et al (1985) in a study in the Bay-Estuary complex of Santos (SP). Concerning C. danae, an evident dominance of females was observed.…”

“…According to Pinheiro et al (1997) in their work in Ubatuba, C. omatus presented a wide ecological niche which overlapped that of other species of portunids, thus being considered a generalist species. Taking this into consideration, we assume that C. omatus, in Guanabara Bay, shows the same behavior described above.…”

Population biology and distribution of the portunid crab Callinectes ornatus (Decapoda: Brachyura) in an estuary-bay complex of southern Brazil

“…However, one clue supporting this hypothesis is that the distribution and salinity were positively correlated, indicating that competition with other species could also explain the low number of the adults in both the estuary and bay. For instance, PINHEIRO et al (1997) found that different swimming crabs can show niche overlap, but that the number of individuals of C. ornatus was lower when in the presence of greater numbers of larger crabs such as C. danae or A. cribrarius. The high proportion of juveniles caught indicates that this species uses the bay for the early part of its life cycle.…”

Biologia populacional e reprodutiva de Callinectes danae Smith (Crustacea, Portunidae), no Balneário Shangri-lá, Pontal do Paraná, Paraná, Brasil

“…Uma distribuição espaço/temporal diferenciada entre os sexos, com migração das fêmeas maturas para a desova, já foi confirmada para outros portunídeos, como C. sapidus (WILLIAMS 1974 ou visando proteção à prole, como a desembocadura de baías, lagoas ou estuários (PITA et al 1985a, PINHEIRO et al 1997, BRAN-CO & MASUNARI 2000. Tal estratégia visa prover um ambiente mais favorável ao desenvolvimento embrionário e larval, além de favorecer a dispersão da prole.…”