Colonization and plasticity in population traits of the invasive Alburnus alburnus along a longitudinal river gradient in a Mediterranean river basin

Abstract

Identification of the most relevant habitat features necessary for the success of potential invaders, such as the bleak Alburnus alburnus with its high ecological risk, is fundamental for understanding the invasive process and, thus, for designing effective control programs. This study provides new insights into the residence time and variation of population traits of this species along a longitudinal gradient in one of the most regulated river basin in the Iberian Peninsula. Occurrence data collected from 25 sampling sites (three times in five years) along the Segura River Basin (SE Spain) showed that this species has spread rapidly and now inhabits more than 168 km of fluvial stretches (84.4% of the studied area). The captured individuals were four years old, although greater longevity and larger mature cohorts were more common in sites with longer residence times. Higher values in population abundance in the upstream part of the river basin were accompanied by increased growth rates and higher maximum sizes. The obtained results support the hypothesis that the wide plasticity of the population traits of A. alburnus plays an important role in its success in a highly regulated Mediterranean river basin, where this mechanism allows it to survive flow regulation events at various scales, as well as to resist the long-term environmental stress typical of Mediterranean-type rivers.