Seasonal patterns of microhabitat selection in the Southern Iberian spined-loach Cobitis paludica

The Southern Iberian spined-loach Cobitis paludica is an Iberian endemism threatened by human activities, including habitat destruction. For this reason, the development of conservation and the recovery plans for the species calls for a precise knowledge of its habitat requirements. Here, microhabitat use and selection patterns were investigated to determine the limiting factors for the species in different seasons, corresponding to a gradient in flow conditions. The microhabitat of the loach was analysed in the River Jarama (Tagus River basin, central Spain) in the period of maximum activity between March and September 2013. No significant differences in microhabitat use were found between males and females, and only very weak ontogenetic changes were detected. The microhabitat used by the loach varied significantly throughout the study period, generally adapting to the flow-mediated dynamics of available habitat. The most stable pattern throughout the year was the use of very low water velocities. Additionally, the loach made selective use of certain microhabitat features, with slight adjustments to the seasonally changing habitat conditions. The loach significantly selected positions with abundant silt substrate and aquatic vegetation, and avoided coarser substrates. The availability of fine substrates and abundant vegetation is therefore a critical habitat requirement for the loach, which needs instream structures that provide foraging substrate, refuge and safe positions for spawning. Selection of refuge elements (deep habitats, aquatic vegetation) was especially apparent under low-flow conditions. Human activities leading to the loss of these critical microhabitats may threaten the survival of already scarce loach populations.