Aspectos ecológicos da Ictiofauna da drenagem do Rio do Sono, Bacia do Rio Tocantins, Brasil.
Resumo
The Sono River is a clear-water affluent of the right bank of the upper-middle Tocantins river, formed by the rivers Novo and Soninho. This work aimed to investigate the biotic or abiotic factors that may influence the structure of fish assemblages in the Sono River drainage in three different periods of the hydrological cycle. Fish sampling and environmental variables were performed at nine sampling points, in the months of January 2016 (flood period), April 2016 (ebb period) and June 2016 (drought period), using holding nets, spines, traps, sieves, traps and trawl nets and electrofishing. A total of 1.838 individuals belonging to 111 species, 78 genera, 25 families and seven orders were collected. The most abundant species were Rhinopetitia sp., Bryconops aff. melanurus and Geophagus proximus. An analysis of variance revealed significant differences in the richness recorded during the flood period of those recorded in the ebb and dry periods. The values of abundance and equitability obtained in the drought period were different significantly from those recorded during the flood and ebb period, and a significant difference was observed in the diversity between flood and ebb periods. The temporal difference was significant in the fish species composition between the periods for qualitative and quantitative data. Richness was positively correlated with temperature. Equitability was positively correlated with pH and dissolved oxygen. Richness, abundance and diversity were negatively correlated with turbidity and positively correlated with equitability. The dissolved oxygen had a significant influence on the abundance of the species. In addition to this variable, the distance of the mouth and the total dissolved solids were the variables that showed a strong correlation with the abundance of the species. Was verified a significant difference of the trophic guilds in the three sampled periods. The knowledge of environmental factors, such as dissolved oxygen, turbidity, temperature and pH influencing the structure of fish assemblages, reinforces the need to elaborate management measures that seek to ensure the integrity of the biological assemblages in the Sono River drainage.
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