Temporal distribution of ichthyoplankton in the Ivinhema River (Mato Grosso do Sul State/ Brazil): influence of environmental variables

David Augusto Reynalte-Tataje,Andréa Bialetzki,Rodrigo Fernandes,Keshiyu Nakatani,Angelo Antônio Agostinho

doi:10.1590/s1679-62252011005000017

David Augusto Reynalte-Tataje, Andréa Bialetzki + Show 3 more

Open Access

https://doi.org/10.1590/s1679-62252011005000017

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Abstract

Information on ichthyoplankton is an important tool in determining reproduction periods that - if associated to environmental variables - allows for inferences about the factors that regulate their intensity, beginning, and ending. In this context, this study aims to establish (i) ichthyoplankton composition; (ii) temporal variations in the overall density of eggs and larvae and among the most important taxa; and (iii) the influence of some abiotic and biotic variables on these organisms' abundance. Ichthyoplankton sampling was undertaken during the period between April 2005 and March 2006 at the Ivinhema River, upper Paraná River basin (MS/Brazil). Differences in the ichthyoplankton's temporal variation were evaluated using unifactorial ANOVAs. Principal Component Analysis and Pearson's correlation were used for the relationships between eggs and larvae densities and environmental variables. A total of 3,341 eggs and 2,896 larvae were captured during the period studied, and most of them were medium-sized and large species that carried out some type of reproductive migration. The highest densities of eggs and larvae occurred during the months of spring and summer, except for those of Bryconamericus stramineus, which was most abundant during the winter. The density of ichthyoplankton was most positively correlated with the water's outflow and temperature. However, Plagioscion squamosissimus was positively related to the increase in pH and in zooplanktonic organisms, while B. stramineus was inversely correlated with water outflow and temperature. The study concludes that spawning is most intense in the spring and summer, especially between November and January, and is related to the greatest values of water temperature and outflow. Nevertheless, the response and reproductive intensity in relation to the environmental variables vary according to the species.

Highlights

The period of reproduction for most freshwater fish species is seasonal and related to favorable conditions that maximize fecundation and offspring development (Agostinho et al, 2004)
The species with the greatest temporal amplitude were Plagioscion squamosissimus and Auchenipterus osteomystax, followed by Bryconamericus stramineus. These three species were found in Ivinhema River during the autumn and winter (Table 1)
The larval assemblage found in the Ivinhema River mainly comprised medium and large Siluriformes and Characiformes

Summary

Introduction

The period of reproduction for most freshwater fish species is seasonal and related to favorable conditions that maximize fecundation and offspring development (Agostinho et al, 2004). Studies carried out at the Prata basin have shown that, in general, fish’s reproduction occurs from October to March (Baumgartner et al, 1997, 2004; Bialetzki et al, 2005; ReynalteTataje et al, 2008; Tondato et al, 2010) and the main environmental variables responsible for the ichthyoplanktonic community’s distribution are: photoperiod (Vazzoler et al, 1997), temperature (Oldani, 1990; Reynalte-Tataje et al, 2008), outflow and/or increase in water volume (Quiroz & Cutch, 1989; Agostinho et al, 2004), and increases in food availability (Bonetto et al, 1969). The real importance of each of these variables for reproduction is still not totally clear

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