The fish community as an indicator of biotic integrity of the streams in the Sinos River basin, Brazil

Pf Costa,Uh Schulz

doi:10.1590/s1519-69842010000600009

Pf Costa, Uh Schulz

Open Access

https://doi.org/10.1590/s1519-69842010000600009

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Abstract

The basin of the Sinos River, located in the northeastern part of Rio Grande do Sul state, Brazil, has been highly impacted by industrial and urban activities. Water quality is low because of domestic and industrial sewage discharges. Most of the tributaries have suffered drastic structural interventions like canalisations and the removal of riparian vegetation. The aims of this study were to: 1) assess the diversity of fish at 34 sampling sites in twenty-four tributaries of the Sinos River basin; 2) quantify impact level by the Shannon-Wiener diversity index and an adapted Index of Biotic Integrity (IBI); and 3) check the interference of environmental impacts, formerly quantified in a Stream Corridor Assessment Survey (SCAS), on the fish assembly and 4) compare the relationship between the IBI with stream order. Fish sampling was performed by electric fishing in the period from April 2004 to August 2006. A total of 4,869 individuals were sampled, representing 61 species, 14 families and six orders. Significant relationships of the Shannon-Wiener index and IBI with SCAS scores and stream orders were found. Of all impacts that make up the SCAS score, only channel modifications were significantly correlated with IBI. These results indicate that the adaptation of the IBI was effective and performed better than the Shannon-Wiener diversity index when related directly to specific impact categories. The application of the IBI with the SCAS and the other variables was efficient in the tributaries of the Sinos River basin because it showed the biotic degradation in accordance with changes in physical habitat.

Highlights

Aquatic ecosystems have been modified in a significant way due to impacts from human activities
The fish community represented by 61 species was similar to that of a study in the main stem of the Sinos River, where 68 species were recorded (Petry and Schulz, 2006), demonstrating that the diversity of the Sinos River is well represented in the tributaries
The predominance of Characiforms and Siluriforms in streams of the basin of Sinos River, followed the pattern observed in other Brazilian systems (Ferreira and Petrere Jr., 2007; Smith et al, 2003; Suarez et al, 2004; Teixeira et al, 2004, 2005)

Summary

Introduction

Aquatic ecosystems have been modified in a significant way due to impacts from human activities. In Brazil, most IBI studies have been carried out in the states of São Paulo and Rio de Janeiro. Bozzetti and Schulz (2004) adapted IBI for streams from subtropical climates in the southern region of Brazil It takes into account differences in the distribution, abundance, and health of the fishes, which are factors linked with the level and type of modification of the water body (Bozzetti and Schulz, 2004). Most IBIs include abundance metrics from faunal elements specific to the area of investigation The use of these specific metrics impedes the application of a common IBI in different regions of Brazil and decreases the comparability of the results. The specific causes for increase or decrease of IBI scores in different watercourses remain unclear

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