Influence of site characteristics on fish community patterns in French reservoirs

Abstract

– The objectives of this paper are to describe the fish assemblages in French reservoirs and to relate them to the sites' characteristics. The results of 43 fishing surveys were collected and completed with environmental descriptors. Fish assemblages differ between salmonids‐dominated mountain sites and lowland ones. The latter show higher species diversity and a distinction between rheophilic‐ and limnophilic‐type communities. This distinction can be explained by the reservoir age, location in the catchment and depth. The response of fish communities to these variables was investigated by canonical correspondence analysis. It shows that rheophilic species are typically abundant in upper basin, deep and recently created reservoirs. The fish community response to the aging process corresponds to an addition of lowland standing waters species and an extinction of the native riverine ones. The structuring role of the sites' depth, location and age is discussed, considering their relationship with the water body trophic status.

Influence of limnological zones on the spatial distribution of fish assemblages in three Brazilian reservoirs

“…The fish fauna of a freely flowing river constitutes the initial assemblage of the newly formed reservoir. Therefore, the remaining species are often concentrated in tributary mouths, which are more similar to the original habitat than other parts of the reservoir, where their ability to compete and survive is lower (Irz et al, 2002;Oliveira et al, 2004). We observed this pattern in São Simão, where the riverine zone had more native species than the lacustrine zone.…”

“…Dams disrupt migration routes (Hoeinghaus et al, 2009) that are particularly important for fish species with long-distance migrations that depend on long river reaches for reproduction and growth. Many native species are not tolerant enough to become competitive in the new environment because lotic species are replaced by lentic species (Irz et al, 2002;Hughes et al, 2005;Sanches et al, 2016). As a result, the fish assemblage that once inhabited the river is substantially modified.…”

“…Usually, the upper part of a reservoir tends to have riverine features, whereas the N o n -c o m m e r c i a l u s e o n l y lower part has lacustrine characteristics (Irz et al, 2002;Terra et al, 2010;Sanches et al, 2016). However, the presence of tributaries along the reservoir can reset these patterns somewhat (Sanches et al, 2016).…”

“…However, the presence of tributaries along the reservoir can reset these patterns somewhat (Sanches et al, 2016). Freshwater fish species respond differently to these riverine/lacustrine zones because the differing habitat types control the spatial distribution of fish species and the resulting fish assemblages (Holmgren and Appelberg, 2000;Irz et al, 2002;Terra et al, 2010). For example, riverine zones tend to support more native species (Oliveira et al, 2005;Agostinho et al, 2007;Gao et al, 2010) and rare species (Oliveira et al, 2003), whereas lacustrine zones tend to support fewer species (Oliveira et al 2004;Agostinho et al, 2007).…”

Physico-chemical thresholds in the distribution of fish species among French lakes

“…In terms of abundance, fish spatial distributions also generally vary according to an altitudinal gradient. Isolated lakes in high mountains (Alps in the East, Pyrenees in the South-West) usually present a very low fish diversity with low densities Irz et al, 2002), while downstream lake systems, more shallow, warmer and more productive, have generally both higher fish diversity and densities (Downing and Plante, 1993;Brucet et al, 2013). The higher biomass of white bream in the northern part of France above 46.5°N and the clear preference of chub for lakes above 300 m were not expected results (S2).…”