Flash‐flood potential: a proxy for crayfish habitat stability

Abstract

The strength of a population resides in the resilience of its individuals and is closely related to the stability of its habitat. Stream macro-invertebrates are sensitive to environmental changes concerning habitat stability; thus, they require shelter to prevent drift during severe floods. We propose a novel approach to estimate the impact of flash floods upon the substrate, by introducing a variable named 'flash-flood potential' (FFP), which accounts for the site slope and the average slope of the upstream catchment. We investigate the impact of this variable on the distribution of two important crayfish species, Austropotamobius torrentium and Astacus astacus, in Romania. We focus on the connection between crayfish abundance and FFP, and also on the role of the individuals' body size in shelter allocation, considering shelter stability as a key factor in coping with the disturbances. The results show that both species are sensitive to influence of the FFP, A. torrentium apparently having a slight advantage. The size of populations visibly decreased with the increase of FFP, those in the upper range having few individuals, which were mainly found in very stable shelters. Individual analyses reveal that the most durable shelters were generally occupied by the largest crayfish. We hypothesize that the competition for shelter is an indirect driver for preventing the drift of crayfish populations.

Flash-Floods Influence Macroinvertebrate Communities Distribution in Lotic Ecosystems

“…insects and their associated water mite species), upstream migration or from the underneath hyporheic zone (Wallace, 1990; Dole-Olivier, 2011), it seems that the availability of coarse sediments usually associated with high FFP values (Pârvulescu et al, 2016) is not enough to overcome the steepness of slopes and the associated risks for washout during rainy seasons. The implementation of this index within the Romanian territory showed a high correlation not only with the steepness of slopes, but equally with water velocity (Pârvulescu et al, 2016). Although certain groups of mayflies (e.g.…”

“…1). We have focused on log-linear models because of monotonic response expected for invertebrates to FFP variation (Pârvulescu et al, 2016). All tests were undertaken in XLSTAT version 2010 package.…”

“…Therefore, FFP estimates, the potential for disturbance in streams, by taking into account the potential drainage velocity both upstream and at the site. For further details, we refer readers to Pârvulescu et al (2016).…”

“…To overcome the knowledge gap induced by the combination of several detrimental events associated with floods, a new variable, named "flash-flood potential" (FFP) was proposed to estimate the impact of irregular high flows upon substrate availability and hence of the invertebrate community stability in streams (Pârvulescu et al, 2016). The FFP accounts for the site slope and the average slope of upstream basins and proved to be a good indicator for assessing the spatial distribution of different size-classes of crayfish in rivers (Pârvulescu et al, 2016). This study goal was to test how this variable predicts the occurrence of various groups of macroinvertebrates inhabiting lotic systems covering a wide variety of catchments slopes within Romania.…”

The future of endangered crayfish in light of protected areas and habitat fragmentation

“…refs. 30 – 32 ). The SRTM V3 void filled 33 digital elevation model (DEM) at a 100-m resolution was processed and used for the extraction of the river network of the analysed area in ArcGIS version 10.4 (ArcMap; Environmental Systems Resource Institute, Redlands, California).…”