Passage denied: The potential of dispersal barriers to limit the spread of aquatic invasive species through shipping canals

The spread of aquatic invasive species (AIS) presents a pressing challenge for global biodiversity, with freshwater ecosystems being particularly affected. The connection of watersheds throughout Europe by the construction of artificial shipping canals has created novel invasion pathways, but may also provide critical infrastructure to counter range expansion by implementation of different barrier solutions. Here, we critically review the efficacy, applicability and limitations of dispersal barriers against AIS in shipping canals considering fishes, invertebrates, algae, bacteria and fungi. Despite the wide spread of AIS and their known detrimental effects on aquatic ecosystems, research focusing on barriers for AIS in shipping canals is rather limited and predominantly concentrated on a few species of fish. Out of 180 screened studies, only 32 examined the efficacy of technologies such as electric fields, acoustic signals, strobe light, air-bubble curtains, CO₂ and pheromones as non-physical barriers. Efficacy and applicability was mostly tested in laboratory setups and strongly species-dependent, requiring a site-specific identification of the most useful barrier technology. Major limitations to barrier implementation include undesired and unknown side effects on non-target species, humans and the environment. To preserve the ecological integrity of freshwater ecosystems across transboundary and inland watersheds, future research should tackle these challenges by increasing the number of studies under realistic field conditions to allow evidence-based decision making on the management of AIS.