Abstract:The streams of the Eastern Basin are characterized by being small, somewhat complex and endemic fish fauna due to geographical isolation. In this context, a study of species distribution and community structure of stream fish Limoeiro, BA along a spatial gradient in one year, using electrofishing as the collection method. Twenty one fish species were collected totalizing 2264 specimens in four points: two points near the head (P1A and P1M), one in the middle course (P2) and another near the mouth (P3). Characiformes and Siluriformes were the orders more important among the four registered. Some species occurred exclusively at the head (Astyanax sp. and Trichomycterus cf. bahianus) and other near the mouth (Leporinus sp. and Callichthys callichthys). On the other hand, Characidium zebra, Parotocinclus cf. cristatus, Poecilia vivipara, Astyanax sp.1, Rhamdia sp. and Poecilia reticulata occurred all sampling points. Was collected one specie the "status" of vulnerable (Nematocharax venustus) and two exotics (Tilapia rendalli and Poecilia reticulata). About the community structure, the values of the index of richness of "Margalef" and of the index of diversity of "Shannon" were greater in this point P3, then this point were significantly lower value of "Berger-Parker" dominance index. The point with riparian vegetation preserved (P1M) showed a lower average water temperature and the points near the head (P1A and P1M) showed the highest values of dissolved oxygen and surface velocity. Conductivity, width and depth of the medium increased toward the mouth. Several results are in accordance with the current literature dealing with community ecology of neotropical stream fish.

AIM: in this study we present data from the diet of Astyanax vermilion which were used as a tool to compare two sites of streams with different vegetation cover in Ribeirão Limoeiro, Cachoeira River Basin, BA. METHODS: Four samples were taken (March, June, September and December) using electrofishing as the collection method in two contiguous sites of the headwaters: stretch without riparian vegetation and with riparian vegetation. RESULTS: The qualitative composition of the diet was analyzed by the method of frequency of occurrence. The allochthonous resources of vegetal origin made up the bulk of the diet in the stretch without riparian vegetation with a frequency of occurrence of 64%. In the section with riparian vegetation allochthonous resources of animal origin made up the bulk of the diet with a frequency of 62%, which emphasizes the importance of food items from the surrounding environment. The mean Shannon diversity index, calculated from the frequency of occurrence of food items was significantly different (p = 0.04) when comparing reach deforested (H'= 1.44) with reach forested (H'= 1.80). The average weight of stomachs in the deforested reach (WS D = 0.18g) was significantly higher than that of the forested reach (WS F = 0.14g). CONCLUSIONS: in the stretch with riparian vegetation, the food diversity was greater and the fish that are in the riparian stretch do not need as much food to satisfy their physiological needs. These results underscore the importance of the type of riparian vegetation as a food source for fish

No abstract

Serrasalmus brandtii and Pygocentrus piraya are two common piranha species in the Barragem da Pedra Reservoir, rio de Contas. In order to identify the diet composition of the two species, monthly collections were performed at three sites between May 2001 and April 2003, using two gill nets of different mesh sizes cast at the beginning of the day and visited after 6, 12 and 24 h. The qualitative composition of the diet was analyzed by determining the frequency of occurrence. Comparison of the two species showed a higher relative abundance of S. brandtii (151) compared to P. piraya (55). The food items most frequently found in the stomachs of the two species were fins, fish and shrimp. Serrasalmus brandtii showed a greater feeding plasticity than P. piraya.
Serrasalmus brandtii e Pygocentrus piraya são duas espécies de piranhas comuns no reservatório da Barragem da Pedra, rio de Contas. Com o objetivo de identificar a composição da dieta das duas espécies, foram realizadas coletas mensais em três pontos no período de maio de 2001 a abril de 2003, tendo em cada ponto duas redes de espera com malhas distintas, colocadas no início do dia e visitadas após 6, 12 e 24 horas. A composição qualitativa da dieta foi analisada com uso do método de freqüência de ocorrência. A comparação realizada entre as duas espécies descritas revelou haver uma maior abundância relativa de S. brandtii (151) em relação à P. piraya (55). Os resultados indicaram que os itens: nadadeira, peixes e camarões foram os itens encontrados com maior freqüência nos estômagos de ambas as espécies. Serrasalmus brandtii mostrou uma maior plasticidade alimentar do que a P. piraya

The variation in water level in the Amazon várzea promotes cyclical isolation or union of various bodies of water. Among these, lakes and channels are the most relevant. Due to their cyclical geographic isolation, and even due to the often distinct origin of their waters, these environments showed limnological features which also vary from those bodies of water located outside the várzea setting. The objective of this study is to demonstrate the differentiation of the types of water bodies present in the Middle Solimões area, inside and outside of the floodplain areas, by segregating their main physical and chemical parameters. It also aims to evaluate the influence of the flood pulse on these parameters in these types of bodies of water. In order to do this, expeditions were conducted monthly from 2004 to 2011, at twelve sampling stations located in different types of water bodies, including canals and lakes within the Mamirauá Sustainable Development Reserve, the Solimões River and the mouth of the Tefé River. The parameters monitored were electrical conductivity, temperature, dissolved oxygen, oxygen saturation, pH and transparency. To analyze the data obtained from this monitoring, descriptive statistics and clustering were used. The temperature of the bodies of water in the Mamirauá RDS showed mean values ranging between 27.1 and 30.8 ° C. Dissolved oxygen concentrations resulted in average concentrations of from 0.3 to 0.6 mg.L-1, with a high standard deviation. Transparency was between 0.4 and 1.6 m. Electrical conductivity ranged between 87 and 204 μS.cm-1 in white waters and 10 -21 μS.cm-1 in black/mixed waters of the mouth of the Tefé River. From the groupings obtained, it was possible to state that the lakes behave like independent bodies of water in the daught season, and during the season of high water they form a large grouping, suggesting a greater homogenization. An analysis of principal components with the parameters confirmed their relevance in the structuring of groups or types of bodies of water identified in the region. The pH distinguished itself as the main differentiating factor between white and black waters, followed by water transparency. Electrical conductivity was the main parameter responsible for the differentiation of water in different periods of the hydrological cycle, followed by water transparency. The variation in water level during the hydrological cycles evaluated over seven years of monitoring influenced the water quality in the lakes and canals of Mamirauá Sustainable Development Reserve and the Solimões and Tefé Rivers. The parameters transparency, dissolved oxygen, and conductivity varied more markedly between the periods of draught and high water.