Invasive Species Impacts on Freshwater Fish Biodiversity

Invasive species represent one of the foremost threats to freshwater fish diversity, acting through competition, predation, habitat alteration and the introduction of novel pathogens. Aquatic invaders such as the topmouth gudgeon and associated fungal-like parasites can drive local extinctions by outcompeting native species for resources, disrupting food webs and acting as reservoirs for generalist pathogens. The ecological consequences extend from altered species assemblages and reduced genetic diversity to impaired ecosystem functioning and economic losses in fisheries and aquaculture. Global vectors of introduction include the aquarium trade, live fish stocking, unregulated ballast water discharge and waterway connectivity projects. Effective management relies on early detection, risk mapping, biosecurity controls and rapid response protocols to prevent establishment and mitigate impacts on native fish communities.

Research from Nature Portfolio

Recent studies have advanced our ability to forecast and manage biological invasions in freshwaters. Ensemble ecological niche models trained on climate and occurrence data have revealed hotspots of suitability for non-native fishes far beyond their current ranges, informing targeted surveillance and early-warning systems. Experimental infection trials coupled with epidemiological modelling have clarified the interplay between direct and environmental transmission of fungal-like pathogens, demonstrating that reservoir hosts can sustain high pathogen loads and that transmission dynamics shift once native hosts become infected. These insights underpin integrated prevention strategies combining stringent biosecurity measures with timely eradication of high-risk species to curtail novel disease outbreaks.

Invasive Species Impacts on Freshwater Fish Biodiversity publication trend

The graph below shows the total number of articles in invasive species impacts on freshwater fish biodiversity across all publications each year (not limited to Nature Index journals).

Technical terms

Biotic resistance: The capacity of native species assemblages to limit the establishment or spread of invasive organisms through competition or predation.

Ecological niche model: A quantitative framework predicting a species’ potential geographic distribution based on environmental variables and occurrence records.

Environmental DNA (eDNA): Genetic material released by organisms into water or sediment, used as a non-invasive method to detect species presence.

Reservoir host: A species that harbours a pathogen without severe effects, maintaining the disease agent and facilitating its transmission to other hosts.

References

1. Emergence of the Fungal Rosette Agent in the World: Current Risk to Fish Biodiversity and Aquaculture. Journal of Fungi (2023).
2. The alternate role of direct and environmental transmission in fungal infectious disease in wildlife: threats for biodiversity conservation. Scientific Reports (2015).
3. Predicting global invasion risks: a management tool to prevent future introductions. Scientific Reports (2016).
4. Impact of the invasive alien topmouth gudgeon (Pseudorasbora parva) and its associated parasite Sphaerothecum destruens on native fish species. Biological Invasions (2019).
5. Trophic Plasticity of the Highly Invasive Topmouth Gudgeon (Pseudorasbora parva) Inferred From Stable Isotope Analysis. Frontiers in Ecology and Evolution (2020).
6. Phylogenetic and environmental DNA insights into emerging aquatic parasites: implications for risk management. International Journal for Parasitology (2018).