Abstract
Non-native invasive species are a major threat to biodiversity, especially in freshwater ecosystems. Freshwater ecosystems are naturally rather isolated from one another. Nonetheless, invasive species often spread rapidly across water sheds. This spread is to a large extent realized by human activities that provide vectors. For example, recreational boats can carry invasive species propagules as "aquatic hitch-hikers" within and across water sheds. We used invasive gobies in Switzerland as a case study to test the plausibility that recreational boats can serve as vectors for invasive fish and that fish eggs can serve as propagules. We found that the peak season of boat movements across Switzerland and the goby spawning season overlap temporally. It is thus plausible that goby eggs attached to boats, anchors, or gear may be transported across watersheds. In experimental trials, we found that goby eggs show resistance to physical removal (90mN attachment strength of individual eggs) and stay attached if exposed to rapid water flow (2.8m·s(-1)for 1h). When exposing the eggs to air, we found that hatching success remained high (>95%) even after eggs had been out of water for up to 24h. It is thus plausible that eggs survive pick up, within-water and overland transport by boats. We complemented the experimental plausibility tests with a survey on how decision makers from inside and outside academia rate the feasibility of managing recreational boats as vectors. We found consensus that an installation of a preventive boat vector management isconsidered an effective and urgent measure. This study advances our understanding of the potential of recreational boats to serve as vectors for invasive vertebrate species and demonstrates that preventive management of recreational boats is considered feasible by relevant decision makers inside and outside academia.
Highlights
Individuals of any purely aquatic species cannot move freely between water bodies because of the dendritic nature of watersheds and due to the isolation of catchments from one another (Thienemann 1950)
We empirically address the plausibility of recreational boats as vectors and goby eggs as propagules as well as the feasibility of management based on the following questions: (1) Do vector and propagules temporally overlap in activity to make a pick up and translocation plausible? (2) Are propagules able to survive conditions during a translocation? (3) How do relevant decision makers value a preventive management of the vector? To address question (1), we examine the temporal overlap of vector movements and propagule availability using data on local boat movements and on the local goby spawning season
Our results confirm the plausibility of recreational boats as vectors of goby eggs
Summary
Individuals of any purely aquatic species cannot move freely between water bodies because of the dendritic nature of watersheds and due to the isolation of catchments from one another (Thienemann 1950). It is intriguing that aquatic ecosystems are disproportionally impacted by rapid range expansions of invasive species across watersheds (Rahel 2007). Humans break down natural barriers to dispersal in aquatic ecosystems by, for example, building shipping ways that connect major catchments (Rahel 2007). The Rhine–Main– Danube channel provides a link between two major European watersheds. Humans provide vectors which realize the uptake of propagules in one system, the translocation, and the release into another system (Johnson et al 2001).
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