A spatially‐explicit assessment of the fish population response to flow management in a heterogeneous landscape

Abstract

Ecological processes are structured in space and there are important benefits in incorporating spatial information for the analysis of data sets obtained from field studies. Assessing the effect of different flow management practices on river ecosystems is an example where such an exercise is highly relevant. Human activities such as hydroelectric power production are known to modify the temporal variability in river flow. Flow management strategies may have a direct influence on fishes and may trigger complex cascades of interactions involving different features of the river ecosystem. In this study, we performed an assessment of the effect of different flow management practices on fish count density (no. fish/m2), biomass density (g/m2), and species richness. Data were collected in 941 sites located along 28 Canadian rivers. These rivers were either naturally flowing or had altered flows from one of three flow management strategies: run of the river dams, storage with gradual release, or storage with peak release. Each site (300 m2) was surveyed using paired snorkeling and electrofishing techniques; environmental variables (water depth and velocity, and substrate composition) were also measured. The study spanned a broad geographic range (3497 km, geodesic distance) and involved repeated local observations (16–50 sites/river), and was therefore inherently spatially organized. We used spatial modeling to obtain a baseline to estimate the effect of flow management strategies on fishes. Our results indicate that rivers downstream of flow peaking storage dams have, by far, the lowest fish densities (count and biomass) and species richness, whereas those downstream of gradual release storage dams had higher fish biomass density than the unregulated rivers.

Modelling habitat distributions for multiple species using phylogenetics

“…). That result concurs partially with that of Guénard et al (), who found a negative impact of flow regulation by FS dams on total fish density. In contrast with that study, however, we found here that RR and ST dams seem to affect even more species than FS facilities.…”

“…As a demonstration of the practical utility of the approach, we used phylogenetic habitat modelling to assess the effect of flow regulation by hydroelectricity production companies on fish species in rivers. That data set, had previously been used by Guénard et al (), who analysed the effect of water regulation on total fish density and species richness. Here it has been analysed in greater details to describe fish community structure in river sampled over a broad geographic range and make specific predictions for regulated sites.…”

“…As a demonstration of the practical utility of the approach, we used phylogenetic habitat modelling to assess the effect of flow regulation by hydroelectricity production companies on fish species in rivers. That data set, had previously been used by Guénard et al (2016a), who analysed the effect of water regulation on total fish density and species richness.…”

“…Hence, the few species that were affected by FS dams were observed in large numbers, while many species affected by RR and ST dams were only sparsely observed and had little impact on total fish density. The analysis performed in the present study can therefore be regarded as more sensitive than that of Guénard et al (2016a) to detect the influence of flow regulation on fish densities, in addition to providing more detailed information about fish community responses to flow management.…”

Short Communication: The effect of water quality on the population density of Pterygoplichthys pardalis in the Ciliwung River, Jakarta, Indonesia

“…The current velocity of a flowing body of water, such as a river, determines the spread of organisms and the availability of food sources for aquatic biota. The stronger the current velocity is, the greater the abundance of food sources is, which also leads to the better spread of fish, and ultimately affects population density (Hockley et al 2013;Guenard et al 2015).…”