Environmental factors related to entry into and ascent of fish in the experimental ladder located close to Itaipu Dam
Carregando...
Data
2007-06
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Ictiologia
Resumo
We evaluated the seasonality of the ascent of fish in an experimental ladder located close to Itaipu Dam, and its relationships to reproduction, temperature, river level and discharge. Samplings of fish and measurements of abiotic factors were performed from February, 1995 through January, 1997, in two resting pools of the ladder. Pool A was located 10 m above the mean level of the Paraná River; Pool B was located at the upper end of the ladder, at a height of 27 m. Autoregressive models were used to
remove the temporal dependence between observations. Residuals of the models were used to relate, using Pearson’s correlation coefficient, the densities of fish to the environmental variables. Clear patterns of seasonality were observed for temperature. River level, turbine discharge and spillway discharge, although they showed no clear seasonal dynamics, were timedependent, because the autocorrelation coefficients for different k values were significant. In the samples of larger-sized fish,
23 species were recorded during the two years of study. Most of the individuals were in a non reproductive state, and about 90% of the individuals belonged to only six species. The temporal variability in total abundance, considering all species, indicated a pattern of seasonal variation; high abundances occurred from October through February (75%) and in Pool A (61%
of the 1343 individuals sampled). Low abundances were recorded during winter, with the correlogram of total density confirming this tendency. In the samples of smaller-sized species, six species were recorded, with all six present in both pools, but more frequent in the first pool (64%). Bryconamericus stramineus comprised 99% of the total numbers of smaller fish in the samples. The total abundance of small species showed different temporal patterns of seasonal variation in the two years of study.
Descrição
Palavras-chave
Fish ladder, Fish migration, Environmental factors, Paraná river
Citação
FERNANDEZ, D.R.; AGOSTINHO, A. A.; BINI, Luis Mauricio; GOMES, L. C. Environmental factors related to entry into and ascent of fish in the experimental ladder located close to Itaipu Dam. Neotropical Ichthyology, Maringá, v. 5, n. 2, p. 153-160, Apr./June 2007.