A survey performed in the Guaratuba Bay (25º52'S; 48º39'W) and the adjacent marine area has provided additional data about the habits of the croaker in the southern coast of Brazil. A dynamic pattern of movements along the marine and estuarine waters was observed, but it does not indicate spawning activity in the study area. During autumn/winter, pre-adults and adults use the marine waters. In spring/summer, following gonadal maturation,the individuals leave this area and probably move to deeper waters, where they spawn. Until the end of summer, the estuary is then occupied by juveniles coming from the marine spawning area. In autumn/winter, these juveniles and the new pre-adults move to the marine zone adjacent to the bay and begin gonadal maturation. It is suggested that the Guaratuba Bay and the adjacent marine area constitute an important site for growth and recruitment of the early lifestages of M. furnieri and initial stages of reproductive activity.

A survey performed in the Guaratuba Bay supports the hypothesis that the G. melanopterus individuals migrate to reproduce at the sea during summer. In autumn and winter, the adults return to the Bay, a pattern not yet described in the literature for this species. G. melanopterus explores the most internal areas of the Bay when the continental influence is lower. Differences in feeding habits were registered between individuals occupying the investigated area and those from a nearby mangrove previously studied.

No manguezal da Baía de Guaratuba, litoral sul do Brasil, os Gerreidae são representados por 3 gêneros e 5 espécies, compondo uma parcela numericamente importante da ictiofauna local. Este trabalho descreve a estrutura populacional e os hábitos reprodutivos de Eucinostomus argenteus, E. gula e E. melanopterus, reconhecendo as relações que mantêm com o manguezal. Os resultados indicam que o manguezal representa para elas um habitat transitório. Os subadultos crescem na área ao longo do ano, deixando-na na primavera ou no verão, quando completam a maturação e desovam, no mar ou em outra região da Baía. E. argenteus e E. gula não retornam ao manguezal após a desova, mas E. melanopterus provavelmente sim. As três espécies alimentam-se sobretudo de poliquetos, apresentando diferenças nos itens secundários da dieta.

Several coastal fish use the estuarine habitat during a part of their life cycle. These sites are considered good for the reproductive activity, as well as for the growth of larvae and juveniles. Concerning the Gerreidae, however, many studies reveal that most species leave the estuaries to reproduce at sea. At Guaratuba Bay, southern Brazil, this family is represented by three genera and five species, which make an important fraction of the local assemblage. The present study investigated the populational structure and breeding habits of three Eucinostomus species, in order to know what relationship exists between them and the mangrove. It was found that the Guaratuba mangrove represents a transitory habitat for the life cycle of the Eucinostomus species. The sub-adults grow in the mangrove throughout the year and leave this milieu in spring or summer, when they complete the gonadal maturation and presumably spawn. E. argenteus and E. gula do not return to the mangrove after spawning. The three species feed mainly on polychaetes, but differences occur with respect to the secondary components of the diet.

A alimentação do cangulo ou canguá, Stellifer rastrifer, foi estudada no manguezal da Baía de Guaratuba entre fevereiro 1996 e fevereiro 1997. Constatou-se que a dieta está baseada em invertebrados, sobretudo Decapoda Brachyura e Polychaeta. Secundariamente, registram-se vegetais superiores, Copepoda, Gammaridea e Mollusca. O grau de participação dos itens varia com a estação e o tamanho dos indivíduos. Tal plasticidade no hábito alimentar, também conhecida em outras populações de peixes estuarinos, pode ser considerada como mais um indicador do grau de instabilidade encontrado nestes ambientes.

Feeding habits of Stellifer rastrifer (Perciformes, Sciaenidae) at Guaratuba mangrove, Parana, Brazil, were studied from February 1996 to February 1997. It was observed that its diet was based on invertebrates, mainly Decapoda non-Brachyura and Polychaeta. In a smaller proportion there were plants, Copepoda, Gammaridea and Mollusca. The level of contribution of each food item changed according to the season and the individual size. Such plasticity in feeding behaviour was similar to that described to some fish populations from other estuaries, and could be an indicator of the high level of instability presented by this kind of ecosystem.

The species of Citharichthys Bleeker, 1862, C. arenaceus Evermann & Marsh, 1900 and C. spilopterus Günther, 1862, are the most common flatfishes found in Guaratuba Bay, south Brazil. Different size categories of these flatfish occur in the mangrove area throughout the year. The Gonadosomatic Index, the Condition Factor, and the morphological analyses of the gonads from samples obtained between 1994 and 1996 reveals a spawning activity during late Spring and early Summer. This period coincides with the increase in temperature and decrease in salinity. Spawning evidence and the presence of ali size categories throughout the year indicate that Citharichthys spp. are permanent inhabitants of the mangrove in Guaratuba Bay, where they complete their life cycle.