Flash‐flood potential: a proxy for crayfish habitat stability

Abstract

AbstractThe 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. Copyright © 2016 John Wiley & Sons, Ltd.