Abstract
The introduction of non-native species and human-altered habitats are currently the main threats to freshwater ecosystems. Due to predation and competition, biological invaders can cause extinctions and imperil the status of native species, and this phenomenon is enhanced by habitat alteration, for example, dam construction. In addition to river fragmentation caused by dam construction, the impact of non-native species migrating from reservoirs on native assemblages in their tributaries should be considered from a long-term perspective. The present study focused on asp (Leuciscus aspius), an artificially introduced piscivorous cyprinid that became established in the Lipno Reservoir (Czech Republic). Asp regularly occur in a tributary, the Vltava River, where twenty-five individuals were captured, radio-tagged, and tracked for five consecutive years. Asp occurrence in the tributary was highest during spring due to the upstream migration of spawning fish, and this was interconnected with a movement activity peak in March when the temperature reached 6 °C. The fish migrated a maximum distance of 31 km, and the probability of asp occurrence in the tributary was sex-dependent, with more females than males. Some individuals occupied the Vltava River not only for spawning but remained until the temperatures dropped below 10 °C. This study shows how non-native predators use reservoirs for wintering but feed and spawn in tributaries.
Highlights
The introduction of non-native species (NNS) often ensues as a result of anthropogenic disturbance and is one of the main threats to the biodiversity of freshwater ecosystems [1,2,3]
This finding was supported by the fact that the probability of occurrence in the Vltava River was highest during spring (χ2 = 83.93, d.f. = 3, p < 0.0001; Figure 2) and that the peak of movement activity occurred in March (F6,81.6 = 3.62, p < 0.0031; Figure 3)
One of the threats to freshwater biodiversity is the introduction of non-native species in anthropologically altered habitats [2]
Summary
The introduction of non-native species (NNS) often ensues as a result of anthropogenic disturbance and is one of the main threats to the biodiversity of freshwater ecosystems [1,2,3]. The rate of introductions and the patterns and threats associated with biotic invaders reflect the patterns of human activities, all of which have increased substantially in recent decades. Human population growth and movement, global trade, and environmental alteration have together created great opportunities for unintentional introductions [7,8]. Anthropogenic non-native fish introductions are often driven by economic benefits and often occur alongside the globalization of fish culture based on introduced species [5,9].
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