Stretching more than seven million square kilometers, the Amazon River basin is the largest river basin in the world and discharges about one-sixth of all freshwater from the continents to the oceans of the world. The age of this ecosystem, its position near the equator and the enormous diversity of its aquatic habitats, have produced the most diverse fish fauna on the planet. About 2,500 fish species have already been described and it is estimated that more than 1,000 new species remain to be discovered. Knowledge concerning this multitude of fish species is still insufficient, which makes their management and protection difficult. About 50% of the species are thought to occur in the large rivers and connected floodplains and another 50% in headwater streams. Inland fisheries give rise to 450,000 t of fish each year and thus contribute substantially to the protein supply of local populations. However, despite their economic importance, these fisheries receive little attention from the respective governments. The fisheries are highly selective and several stocks of large species with high market value have been over fished. Fish culture is still in its infancy but its development is expected to provide high-quality species during periods of low supply. Over large areas, aquatic habitats are still in near-natural conditions because of the low densities of resident human populations. Nonetheless, over the last few decades, the pressure on aquatic ecosystems and habitats has steadily increased, mainly due to large-scale destruction of natural vegetation cover by agro-industries in the savanna belt (cerrado), small-scale agriculture in the Andean hill slopes, and logging in rain forests. These activities have placed aquatic biodiversity, including fishes, at serious risk. Many headwater species have restricted distributions and are therefore particularly vulnerable to large-scale environmental degradation. Moreover, the construction of large reservoirs for hydroelectric power generation has serious consequences for fish fauna. Currently, about 16.4% of the Amazon River basin is protected, and another 15.2% is under partial protection in indigenous reserves in Brazil. Another 9.1% will be implemented as reserves in the next 10 years in the Brazilian part of the basin. The formulation by the Amazonian countries of a coherent policy that integrates long-term management of the river basin with sustainable management of aquatic and wetland habitats, including their fauna and flora, is urgently needed
In a tropical floodplain lake in central Amazon (L. Camaleao), we investigated seasonal shifts in primary carbon sources for commercially important fish species over an hydrological cycle. Carbon and nitrogen stable isotope and stomach content analyses were conducted to investigate the feeding preferences of six species with different feeding habits: Cichla monoculus (piscivorous species), Schizodon fasciatus (herbivorous), Prochilodus nigricans (detritivorous), and the omnivorous species Triportheus angulatus, Colossoma macropomum and Mylossoma duriventre. Stomach content and isotopic analyses exhibited a high seasonal variation for four out of the six species. The dominant food items were fruits and seeds, plant material, zooplankton and aquatic and terrestrial insects. Over the hydrological cycle, C-3 plants were the major carbon source for all fish species. In addition, seston and aquatic C-4 macrophytes were very important carbon sources for most species. Our findings underpin the complex trophic linkages between floodplain lakes and the aquatic terrestrial transition zone as postulated by the Flood Pulse Concept
ResumoNeste trabalho são discutidas a alimentação e a reprodução de 20 espécies de peixes coletadas no igarapé do Porto, Aripuanã, MT, no início do período chuvoso. Baseado nas análises do conteúdo estomacal e algumas vezes intestinal, discute-se a distribuição das espécies nos diversos biótopos estudados, mudanças de hábitos alimentares e preferência por determinado tipo de alimento dentro de vários níveis tróficos: consumidores primários, secundários e terciários. São incluídas ainda, éllguméls observações sobre -a época de reprodução das espécies estudadas. INTRODUÇÃOA Amazônia com uma extensão de quase 7 milhões de km 2 , inclui parte da Bolívia, Peru, Guiana, Colômbia, Venezuela e uma grande área do território brasileiro. Os rios amazôni-cos são alimentados principalmente pelas águas resultantes das precipitações que acorrem nos Andes, Brasil Central, Guianas e Baixo Amazonas, sendo que seus trechos navegá-veis correspondem a cerca de 40.000 km 2• Em virtude do tamanho da área de drenagem e do clima chuvoso que predomina na região, o volume médio d'água lançada no mar pelo rio Amazonas, por ano, está acima de 200.000 m 3 / seg. Este rio representa, portanto , o maior sistema fluvial do mundo; sua vazão correspende a quinta ou sexta parte da massa total da água levada para o oceano.A elevada quantidade de água que o Amazonas carreia cont inuamente para o oceano, origina-se, em parte, nos inúmeros igarapés encontrados em sua vasta área de tributários. Foi estimado que a soma das superfícies dos pequenos igarapés seria muitas vezes maior que o múltiplo da superfície do Amazonas e Maria Gercília Mota Soares (**) que a soma dos comprimentos formaria um curso d'água mil vezes maior que o do próprio rio (Fittkau, 1967) .Em geral as igarapés possuem uma fauna rica em espécies animais, principalmente peixes. Segundo Fittkau (1974). mais de 100 espécies de peixes podem ser coletadas no curso superior de um igarapé nas proximidades de Manaus e cerca de 300 invertebrados podem ser distinguidos macroscopicamente. O mesmo autor menciona ainda que em uma área de 300 m de comprimento e 2-3 m de largura, uma amostra quantitativa produziu 17 espé-cies, resultando uma massa de Sg/ m 2 • LoweMcConnell (1964) capturou em um igarapé d& rio Rupununi , com aproximadamente 50 m de comprimento, 200 peixes representantes de, no mínimo, 17 espécies.Embora existam alguns trabalhos sobre características ecológicas de igarapés da Amazônia (Sioli, 1957(Sioli, , 1964(Sioli, , 1965 Fittkau, 1964 Fittkau, , 1967 Geisler, 1967, Geisler et a/., 1975 Schmidt, 1972; Brinkmann & Santos , 1973), poucos estudos foram feitos relacionando estas características com a fauna dos peixes . Praticamente, tudo o que se conhece está resumido nos trabalhos de Knõppel (1969, 1970). que fez uma avaliação dos principais alimentos ingeridos pelos peixes em igarapés da Amazônia Central e de Saul (1975), que analisou dados climáticos e limnológicos e estudou os hábitos alimentares dos peixes da região de Santa Cecília, Equador.Este trabalho tem por objetivo...
Pronounced seasonal and daily oxygen concentration changes are characteristic for Amazonian floodplain lakes. Studies on the fish fauna of the Lago Camaleão, Solimões River, Amazonas, Brazil, showed several fish species which are able to survive prolonged periods of heavy hypoxia. Twenty species belonging to eight families were observed in the laboratory in order to determine their respiratory adaptations to hypoxic conditions and oxygen concentrations at which the fish present respiratory adaptations. Finally, the fish species were distributed throughout the habitats of Lake Camaleão according to their adaptation responses. Ten fish species used the surface water for aquatic surface respiration, four species used atmospheric oxygen for aerial respiration, four species used oxygen supplied by the exudation of the roots of floating macrophytes and two exhibited a high tolerance to hypoxic conditions, and well-developed physiological biochemical mechanisms. The fish fauna is well adapted to low oxygen concentrations. The large variety of morpho-anatomical adaptations associated with biochemical and physiological mechanisms to tolerate hypoxic and anoxic conditions enable the 20 fish species to exploit several habitats of Lago Camaleão, such as floating aquatic macrophyte meadows, open water and near the shoreline
of pigment biosynthesis is a factor that might promote higher protein contents in this species. Moreover, because of their higher protein and lower chlorophyll contents, the MT01 and MT02 strains are likely candidates to be feedstocks for the development of novel, innovative food supplements and foods.
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