Long-term analysis of fish assemblage structure in the middle section of the Sava River – The impact of pollution, flood protection and dam construction

Marina Piria,Predrag Simonović,Davor Zanella,Marko Ćaleta,Nikica Šprem,Momir Paunović,Tea Tomljanović,Ana Gavrilović,Marija Pecina,Ivan Špelić,Daniel Matulić,Andrea Rezić,Ivica Aničić,Roman Safner,Tomislav Treer

doi:10.1016/j.scitotenv.2018.09.149

Marina Piria, Predrag Simonović + Show 13 more

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https://doi.org/10.1016/j.scitotenv.2018.09.149

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Abstract

At the beginning of the 20th century, the middle section of the Sava River in Croatia was unaffected by major human activities and rich in ichthyofauna. The Sava River was important for commercial and recreational fishing for the local population, which still remains today. However, the 1920s mining industry was established in Slovenia, which emitted carbon dust into the Sava River. At the same time, the construction of embankments to mitigate flooding started in the middle section. Furthermore, in the 1980s, the Krško nuclear power plant (NPP), and in the 2010s, the Krško hydropower plant (HPP) were built in Slovenia. These activities could have an impact on the composition of fish communities downstream from the major sources of disturbances. Therefore, the main aim of this paper were to analyze the changes in fish assemblages of the Sava River from 1978 to 2017, prior to and after the construction of Krško NPP and HPP at the Medsave site on the Sava River, 20 km downstream from the major construction operations. Collected data were divided into four sampling periods (SP): SP1, from 1978 to 1980; SP2, from 1991 to 1994; SP3, from 2001 to 2006, and SP4 from 2011 to 2017. Besides alien fish species, water quality and hydromorphological modifications were identified as significant stressors. In SP1 and SP2 limnophilic and eurytopic fish groups were predominant, and 26 different fish species were identified, but in SP3 and SP4 rheophilic fish groups become dominant, and the diversity has declined to 21 species. Threatened species blageon, Telestes souffia seems to be missing from the main course of the Sava River in last 20 years. It can be concluded that disturbances in the fish assemblage pattern have coincided with the presence of multiple stressors of human origin.

Highlights

Human activities expose inland water ecosystems to a wide range of stressors that threaten freshwater biodiversity and ecosystem processes (Dudgeon et al, 2006; Simonović et al, 2017)
In the Sava River, for the first time three alien fish species were recorded in SP1; these were the North American bullhead (Ameiurus sp.), pumpkinseed Lepomis gibbosus (Linnaeus, 1758) in 1978 and gibel carp Carassius gibelio (Bloch, 1782) in 1979
The importance of the Sava River in history has been focused on commercial and recreational fishing as a basic source of good quality food for local inhabitants, but the number of catch rapidly declined in the second half of the 20th century and available resources remarkably deteriorated (Habeković et al, 1990)

Summary

Introduction

Human activities expose inland water ecosystems to a wide range of stressors that threaten freshwater biodiversity and ecosystem processes (Dudgeon et al, 2006; Simonović et al, 2017). The construction of nuclear (NPP) and hydropower plants (HPP) and their hydrological effects can significantly affect aquatic habitats, organisms and riverine ecosystem processes (Teixeira et al, 2012; Tonolla et al, 2017), and increase the risk of most of the threats identified by Dudgeon et al (2006). Depending on the amount and temperature of the discharged water, heated effluents can induce dramatic and unpredictable climatic and hydrological effects and influence the biological features of the local environment (Rong-Quen et al, 2001). This can affect fish assemblage structures by decreasing species richness and benthic cover, as an indirect impact to the fish community (Teixeira et al, 2009)

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