Hydrological drivers of brown trout population dynamics in France

Abstract

International audienceAlteration of natural river flow regimes is a major threat to freshwater biodiversity. Restoration of natural flow regimes requires an understanding of linked hydrological and ecological processes. In this study, we investigated how annual seasonal flow characteristics and physical habitat attributes could interact to explain yearly changes in brown trout population densities (for 0+ fish, corresponding to the young of the year, and for the >0+ age class) in 112 sites widespread in France. Using an information theoretic approach and general linear modeling, we identified the physical habitat attributes and seasonal hydrological variables which explained 0+ proportion, total, >0+ and 0+ brown trout density dynamics. A decrease in total and 0+ brown trout densities were mainly linked to high water levels in both high and low flows during the emergence period and to a lesser extent, to physical habitat attributes reflecting the river size. 0+ proportions were only linked to the level of low flows, and to a lesser extent to high flows, during the emergence period. Our study demonstrated that seasonality of flow is a main driver of brown trout population dynamics, especially magnitude of high and low flows for the 0+ age class, and should be considered in the definition of environmental flows

Similarity in seasonal flow regimes, not regional environmental classifications explain synchrony in brown trout population dynamics in France

“…The selection criteria and final dataset were the same as those used by Bergerot & Cattanéo (2017). The selection criteria and final dataset were the same as those used by Bergerot & Cattanéo (2017).…”

“…Sites were sampled by wading during autumn to ensure suitable catchability of the 0+ fish, using two-pass removal sampling by electrofishing, which allowed for reliable estimates of fish densities (Bergerot & Cattanéo, 2017;Cattanéo et al, 2002). trutta, European bullhead Cottus gobio, minnow Phoxinus phoxinus, and stone loach Barbatula barbatula) represented on average 92.55 ± 16.03% of the total fish density.…”

“…France: Cattanéo et al, 2002Bret et al, 2016;Bergerot & Cattanéo, 2017, U.S.A.: Zorn & Nuhfer, 2007, Spain: Lobón-Cerviá, 2004, 2007Alonso et al, 2011). These effects have been demonstrated on many streams in countries encompassing very different climatic, topographic, and geological contexts (e.g.…”

“…Fish data were provided by the French National Agency for Water and Aquatic Environments (ONEMA). The selection criteria and final dataset were the same as those used by Bergerot & Cattanéo (2017).…”

“…We expected that the classification defined at the smallest spatial scale would show a stronger relationship to synchrony because microhabitats were known to influence trout populations (Greenberg, Svendsen, & Harby, 1996). We tested the three main variables most likely to explain synchrony in trout populations: (1) spatiotemporal similarities in seasonal flow regimes (Bergerot & Cattanéo, 2017;Cattanéo, Lamouroux, Breil, & Capra, 2002;Cattanéo et al, 2003;Lobón-Cerviá, 2004); (2) spatiotemporal similarities in seasonal temperature regimes (Borgstrøm & Museth, 2005;Elliott, 1981;Hari, Livingstone, Siber, Burkhardt-Holm, & Güttinger, 2006); and…”