Major hydroelectric dams are proliferating in tropical regions such as Amazonia, where extensive new hydropower developments are planned despite potentially severe ecological and social impacts. The status of freshwater biota in the vicinity of existing dams could be valuable to predict the effects of such developments, but detailed ecological monitoring before and after dam construction is frequently lacking. In the absence of these data, we used a space-for-time replacement to compare a key component of the aquatic biota at upstream and downstream sites, with the latter more closely resembling river channel conditions prior to the dam. We assessed the fish assemblages upstream and downstream of the Coaracy Nunes Dam in Amapá, Brazil, the first ecological study at this site since this dam was constructed 42 years earlier. We used gillnets during eight bimonthly field campaigns, covering both wet and dry seasons, and sampled the ichthyofauna (1819 individuals, 81 species) at four sites: Downstream Channel, Reservoir, Upstream Lake and Upstream Channel. We found clear negative impacts on the abundance, biomass, species richness, alpha diversity and species dominance upstream of the dam. The physical subdivision of the river channel and the upstream channel conversion from lentic to lotic habitats were strongly associated with differences in the composition and structure of fish communities. Notable changes include an increased contribution of small-bodied fish in the reservoir and an absence of long-distance migrants upstream of the dam. Downstream channel habitats, in particular, retained their fish diversity with high conservation value typical of eastern Amazonia, yet these areas now face the threat of new hydropower development farther downstream. The long-term impacts on aquatic biodiversity highlighted in this study are especially relevant in the face of burgeoning new hydroelectricity development plans for rivers across lowland Amazonia
We investigated the niche breadth and overlap of the fish species occurring in four environments affected by the Coaracy Nunes reservoir, in the Amapá Brazilian State. Seasonal samples of fishes were taken using a standard configuration of gillnets, as well as dragnets, lines, and cast-nets. Five hundred and forty stomach contents, representing 47 fish species were analyzed and quantified. Niche breadth and overlap were estimated using indexes of Levins and Pianka, respectively, while interspecific competition was evaluated using a null model (RA3). ANOVA and the kruskal-Wallis test were used, respectively, to evaluate differences in niche breadth and overlap between areas. The data indicate that the majority of the fish species belong to the piscivore, omnivore, and detritivore guilds. These species have likely colonized the environments due to the availability of suitable feeding resources, and the favorable physical conditions created by the river damming. Overall, few species have ample niches, but most of them are highly specialized. Resources seasonal variation had little effect on the feeding behavior of most species in the study areas. The null models indicated that competition was not a factor determining on community structure.
A análise temporal da freqüência de estádios de maturação de 102 fêmeas adultas coletadas entre fevereiro de 1979 e janeiro de 1980 na região de Ubatuba, litoral norte do Estado de São Paulo, mostra que M. funieri, nessa área, apresenta três desovas durante o ano: uma no outono (abril-junho), outra no inverno (agosto-setembro) e uma terceira na primavera-verão (novembro-fevereiro). Essa sugestão e reforçada pelas flutuações de K (fator de condição considerando-se o peso das gonadas) e K' (sem considerar o peso das gonadas), durante um ciclo reprodutivo. Os valores máximos de K e K' coincidem com os picos de ocorrencia de indivíduos com gonadas maturas (C) e, os mínimos, com os de indivíduos com gonadas esvaziadas (D), A diferença entre K e K' (AR) estima a "condição da gonada" apresentando seus máximos nos períodos de mais intensa atividade dos ovários, contituindo-se, assim, o valor de AK em um índice indireto de maturidade e dos períodos de desova de M. funieri.
Biological data, size frequency distribution of intraovarian oocytes, maturity indices and histological observations of the gonads were used to assess the spawning cycle of S. brasiliensis. sampled September 1981-August 1982 throughout the main fishing area off the Brazilian coast ( 2 2 3 to 28"s). Post-ovulatory follicles are described and classified, and the incidence of mature females displaying these structures was calculated. The main findings were (a) spawning occurred during the spring and summer with a maximum in December and January; (b) spawning occurred throughout the area studied; (c) spawning was fractional; (d) average batch fecundity was 26 OOO oocytes per female, or 393 eggs g-'; (e) spawning frequency reached values of approximately 50% during the spawning peak, but was sensibly lower during the other months of spawning activity.
In artisanal fishing, the techniques used by a community reflect the characteristics of the natural environment, in particular the distribution and availability of resources, as well as local traditions and customs. However, economic development may result in the loss of these traditions. The present study documents the fishing techniques used by the communities on the Xingu River in the Brazilian state of Pará (Maribel, Altamira, Belo Monte, Vitória do Xingu, Vila Nova, Senador José Porfírio, Porto de Moz, and Gurupá). Interviews were used to investigate traditional local knowledge and the distribution of the different fishing methods within the study area. The local fishers described the use of 12 different types of net, 10 hook and line techniques, and eight kinds of spearfishing. Free diving and scuba diving are also used for the capture of ornamental fish.Keywords: fishing gear, traditional knowledge, Brazilian Amazon basin, small-scale fisheries. Etnoconhecimento e tecnologia da pesca artesanal no Rio Xingu, Pará, BrasilResumo Na pesca artesanal, as modalidades de captura refletem as condições do meio ambiente e as tradições e costumes de uma comunidade. As artes de pesca utilizadas pelos pescadores refletem então, a disponibilidade de recursos e a história cultural de uma região. Contudo, o desenvolvimento econômico pode levar a perda dessas tradições. O objetivo deste trabalho é caracterizar os apetrechos de pesca utilizados pelos pescadores do rio Xingu, assim como seus conhecimentos acerca do uso dessas artes e a distribuição das mesmas ao longo do rio. Para isso foram realizadas visitas em diversas localidades ao longo do rio Xingu (Maribel, Altamira, Belo Monte, Vitória do Xingu, Vila Nova, Senador José Porfírio, Porto de Moz e Gurupá). Através de entrevistas com os pescadores obteve-se uma descrição das artes de pesca utilizadas na região. Os pescadores do rio Xingu utilizam 12 tipos diferentes de redes, 10 métodos de pesca com linha e anzol e 8 tipos distintos de artes de fisgar. Além do mergulho livre e com compressor utilizado na pesca ornamental.Palavras-chave: apetrecho de pesca, conhecimento tradicional, bacia Amazônica Brasileira, pesca de pequena escala.
The present study focused on the fish fauna of the 44-yearold Coaracy Nunes reservoir in the northern Amazon basin, producing estimates of the growth constant (k), maximum and asymptotic body lengths and weights, natural mortality (M), the consumption/biomass ratio (QB) (intake of food by a group over a year), the Aspect ratio (Ar) of the caudal fin, growth performance (Φ), longevity, and trophic level for 45 fish species. Species collection was divided into eight sampling campaigns between May 2009 and July 2010. Gillnets were used in four of the sampling sites. The results revealed that (i) the most predominant species are Ageneiosus ucayalensis, Hemiodus unimaculatus, Serrasalmus gibbus and Geophagus proximus; (ii) small and medium-sized fishes predominated in the community, characterized by high rates of growth and natural mortality, consistent with a predominance of r-strategists; (iii) the body lengths of the detritivore species were similar to those of the piscivores, which are normally larger, but with higher growth rates, more similar to those recorded for the omnivores; (iv) consumption/biomass ratio (QB) 9 body length relationship is higher in the detritivores than in the omnivores and piscivores (which were similar to each other). Overall, the reservoir habitat appears to be advantageous to detritivorous fish species.
Analisaram-se as variações da relaçao gonadossomática (RGS), do comprimento e do peso médios dos ovários por estádio de maturidade e durante um ano, procurando-se estabelecer indicadores quantitativos do grau de desenvolvimento gonadal e dos períodos de desova da população I de Micropogonias funieri. Constatou-se que, para fêmeas num mesmo estádio de maturidade, nao ocorre dependência entre valores individuais de RGS e peso total, sendo a RGS constante para cada estádio, o que permite sua utilização como indicador do grau de desenvolvimento gonadal. Ocorreram variações cíclicas paralelas nos valores dos três indicadores, cujos valores modais coincidem com os períodos de desova (outono, inverno e primavera-verão), o que nos permite utiliza-los como indicadores desses períodos.
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