Abstract
The spatial and temporal distribution of fish eggs and larvae in the Ivinhema River Basin was analyzed. The aim was to determine the spawning areas and their relationship to environmental factors. Monthly collections were done from September, 1994, to February, 1995, in four sites: one in the Ivinhema River and three in different tributaries. Conic-cylindrical plankton net with 0.5 mm, coupled with a flow meter was used, and the samples were preserved in formol 4%. The abundance was standardized for 10 m3. Data related to water temperature, dissolved oxygen, pH, electric conductivity, and rainfall were also collected. Principal Components Analysis determined the correlation between the environmental variables and the ichthyoplankton density along each river stretch. 23,325 eggs and 16,012 larvae were collected. The density was higher during the rainy period. The spawning period coincided with high precipitation level and temperature (October to December), with higher densities on the collect stations of Dourados and Vacaria rivers, with relatively basic pH and low electric conductivity.
Highlights
A bacia do rio Paraná, tendo em vista sua dimensão e potencial pesqueiro, cerca de 10,5% do território brasileiro (Paiva, 1982), tem sofrido grandes represamentos, visando a geração de energia elétrica, o que alterou seu curso natural
Monthly collections were done from September
the samples were preserved in formol 4%
Summary
Foram definidas quatro pontos de coletas, Nascimento e Nakatani distribuídos no rio Ivinhema e nos seus tributários (rios Vacaria, Brilhante e Dourados) (Figura). A constituição do fundo dos rios varia entre cascalho, no Ivinhema e Brilhante a areno-argiloso no Vacaria e Dourados (Vazzoler, 1996). As amostras de ovos e larvas de peixes foram obtidas utilizando-se redes de plâncton do tipo cônico-cilíndrica (malha 0,5 mm), com comprimento de 1,5 m e área de boca igual a 0,07 m2. As abundâncias foram integradas para representar cada ponto amostral e padronizadas para um volume de m3 de água filtrada, segundo Tanaka (1973), modificado por Nakatani (1994). Os parâmetros analisados foram temperatura da água (oC), oxigênio dissolvido (mg L-1), pH, condutividade elétrica (μS cm-1) e dados de precipitação, obtidos de Estações de meteorologia da ANEEL nas respectivas regiões dos pontos de coleta
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