Effect of abiotic variables on fish eggs and larvae distribution in headwaters of Cuiabá River, Mato Grosso State, Brazil

Abstract

Researches on ichthyoplankton seems to be an important tool to identification of spawning areas and periods for freshwater fish. Ichthyoplankton was sampled monthly in the headwaters of the Cuiabá River, upper Paraguay River basin, (Mato Grosso State, Brazil), and in four of its tributaries, between November 2007 and March 2008, to evaluate the spatial and temporal distribution of fish eggs and larvae and the influence of regional and local variables on their distribution. In total, 22,067 eggs and 1,045 larvae were collected. A significant negative correlation was found between egg density and the variables of river level and flow volume. Larval density was not significantly correlated with any of the regional variables. The egg and larval densities were significantly higher at the sampling sites in the main river. The highest densities were found in environments with greater river widths, intermediate depths and lowest values of dissolved oxygen, electrical conductivity, and transparency. Anostomidae, Zungaro zungaro, Bryconamericus spp., Pimelodus spp., Pimelodidae, Auchenipteridae, and Siluriformes were the most abundant groups of larvae, and were observed at the sampling sites in the main river. The study site is an important spawning area for migratory and, non-migratory fish species, and highlight the importance of the main river to the reproductive event, by the influence of local variables transparency and river width, which in turn maybe temporally influenced by the river level.O estudo do ictioplâncton tem se mostrado uma importante ferramenta na identificação de áreas e períodos de desova para as espécies de peixes de água doce.Amostragens de ictioplâncton foram realizadas mensalmente na região de cabeceira do rio Cuiabá, bacia do alto rio Paraguai, (Mato Grosso, Brasil) e em quatro de seus tributários, entre novembro de 2007 e março de 2008, com o objetivo de avaliar a distribuição espaço-temporal de ovos e larvas de peixes. Foram amostrados 22.067 ovos e 1.045 larvas. Identificou-se correlação significativa e negativa entre a densidade de ovos, o nível fluviométrico e a vazão. A densidade de larvas não apresentou correlação significativa com nenhuma das variáveis regionais. As densidades, tanto de ovos quanto de larvas, foram significativamente maiores nos pontos no rio principal. As maiores abundâncias foram observadas em ambientes com maiores valores de largura do rio, valores intermediários de profundidade e menores valores de O 2 dissolvido, condutividade e transparência. Os grupos taxonômicos de larvas mais abundantes foram Anostomidae, Zungaro zungaro, Bryconamericus spp., Pimelodus spp., Pimelodidae, Auchenipteridae e Siluriformes, com maiores abundâncias observadas nos pontos no rio principal. Os resultados mostram que o local de estudo é uma importante área de desova para as espécies de peixes migradores e não-migradores, e destacamos a importância do rio principal para o evento reprodutivo, pela influência das variáveis locais, transparência e largura do rio, que por sua vez parecem ser ...

Distribution of economically important fish larvae (Characiformes, Prochilodontidae) in the Central Amazonia, Brazil

“…The areas at the mouths of lake channels and barrancos, where larvae were concentrated, also had the highest values of dissolved oxygen and conductivity, as well as higher temperature at the time of lowest fluviometric levels. There is a close relationship between environmental factors (temperature, dissolved oxygen, pH, electric conductivity, nutrient availability and photoperiod) and the spatio‐temporal distribution of fish eggs and larvae, as shown in other studies, such as those by Ziober, Bialetzki and Matheus (), Lopes, Garcia, Reynalte‐Tataje, Zaniboni‐Filho and Nuñer (), Ponte et al. (), Suzuki and Pompeu (), Zacardi and Ponte () and Chaves et al.…”

Predicted impacts of proposed hydroelectric facilities on fish migration routes upstream from the Pantanal wetland (Brazil)

“…Existing studies within the basin indicate that the nearly run of the river dams do not substantially alter the long temporal scale (weekly or monthly) hydrology but may influence the sub‐daily hydrology (de Paes et al, ; Fantin‐Cruz et al, ; Zeilhofer & de Moura, ). Given that most spawning happens at night, the sub‐daily adjustments may still impact spawning behavior downstream from the proposed dams (Ziober et al, ). Because spawning often happens in high turbidity waters, presumably to reduce predation, dams which trap fine sediment may reduce population level reproductive success.…”

“…The specific studies in the basin are footnoted by species in Table . The most comprehensive study available is by Ziober et al (), which sampled eight sites in the headwaters of the Cuiabá River for ichthyoplankton abundances. This study reports the presence of Brycon hilarii ( microlepis ), Prochilodus lineatus , Salminus brasiliensis , Hemisorubim platyrhynchos , Pimelodus maculatus , Pseudoplatystoma corruscans , and Pseudoplatystoma fasciatum .…”

Environmental characterization of the reproductive season of migratory fish of the Sinú river (Córdoba, Colombia)

“…In the Cuiba, Mato Gross river (Brazil), the higher densities of embryos and larvae are related to the places with low concentrations of dissolved oxygen, electric conductivity and transparency, larger width of the river and intermediate depths (12). In the flood plain of the upper Parana river, the electric conductivity was positively correlated with the ichthyoplankton density (8); likewise, a positive linear ratio was observed between the abundance of total larvae and the environmental conditions; which suggests that the higher abundance of larvae was related to higher values of electric conductivity and temperature (near 30ºC) (8).…”