Surviving Invasion: Regaining Native Fish Resilience Following Fish Invasions in a Modified Floodplain Landscape

Floodplain ecosystems are focal points for human settlement, and consequently are often subjected to extensive modification and infrastructure development. Establishment of non-native species in floodscapes presents a range of challenges when they become problematic and drive changes in native aquatic communities and ecosystems. These non-native species are often tolerant of reduced water and habitat quality, conferring a competitive advantage over native species. The coupled effects of invasive alien species, landscape modification and floodscape hydrological control collectively reduce ecological resilience, creating feedback loops that reinforce negative effects on native fish. The regulated lower Waikato River floodplain is a New Zealand hotspot for fish introductions, with their proliferation exacerbating the effects of agricultural development, urban expansion, and flood control infrastructure. We argue that the resilience of native fish assemblages to these pressures can be improved through utilizing a series of complementary measures, including enhanced catchment management, strategic alterations to the location, design, and operation of floodplain infrastructure (e.g., gates, pumpstations, and stopbanks), habitat restoration for native fish, and targeted management of invasive species. These measures will need to consider the likely persistence of invasive alien fish, however, to limit their expansion in the face of a changing climate. Although knowledge and implementation gaps exist, tying these strands together presents an opportunity to enhance the resilience of native fisheries into the future. Key to success will be re-thinking floodplain management to include ecosystem services, and this will require ongoing commitment and cooperation amongst all stakeholders to address knowledge gaps and enable effective implementation.

Automated summary

Floodplain ecosystems face challenges from the introduction of non-native species and their impact on native fish and ecosystems. Enhancing the resilience of native fish populations can be achieved through a series of complementary measures.