What to do when invaders are out of control?

Abstract

Biological invasions threaten species and ecosystems worldwide. Impacts from invasions are especially prevalent in freshwaters, where managers have struggled to contain the problem. Conventional approaches to managing invaders focus on prevention and control. In practice, these measures have proven to be variably effective. Control or eradication of established invaders is particularly difficult and, even if ecologically feasible, it may not be socially desirable. Here we propose a new alternative to managing invasive species: managing impact modifiers (MIM). The MIM approach focuses on managing impacts, rather than controlling the invader directly. We reviewed the literature for the world's worst invasive fishes in freshwaters to show there is strong evidence to support the potential for MIM as an effective means of managing impacts of invasions. This included evidence pointing to characteristics of the environment or species themselves that modify impacts of invasions. Detail of three case studies reinforces the potential for MIM as a viable option. Although MIM appears promising, effective application could involve significant investment in an information gathering phase to identify impact modifiers and the means to manage them. Accordingly, MIM is best incorporated into management plans that include a strong learning or adaptive component. Ultimately, MIM may be one of the only viable alternatives for managing invasive species that are truly out of control. This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness

Controlling invasive fish in fluctuating environments: Model analysis of common carp (Cyprinus carpio) in a shallow lake

“…Results of this modeling work highlight the challenge of removal efforts as a means of controlling non‐native fishes, such as carp. Recent reviews of control measures for non‐native fishes documented a series of notable successes, but these were overwhelmingly reported from smaller and more isolated systems (Dunham et al, 2020; Rytwinski et al, 2019). Cases such as the one considered here (large‐open system) represent a major challenge because effectively managing carp in the system under current conditions requires indefinite annual investments in control.…”

“…An example is the interaction between climate change and the spread of non‐native species, which collectively pose urgent threats to global freshwater biodiversity (Hellmann et al, 2008; Perrings et al, 2000; Roy et al, 2014). By altering the physical and hydro‐chemical conditions of freshwater ecosystems, climate change can influence the spread and establishment of non‐native species, as well as efforts to control and suppress these invaders (Dunham et al, 2020; Rehage & Blanchard, 2016). The effectiveness of non‐native species control strategies is of specific importance because these efforts are crucial to mitigating the impacts of non‐native species on freshwater ecosystems (Hellmann et al, 2008).…”

Identifying Priorities, Targets, and Actions for the Long-term Social and Ecological Management of Invasive Non-Native Species

“…Resolving these trade-offs will require further analyses to evaluate which solutions achieve the most effective management outcomes. Guidance and criteria for assessing and ranking more detailed activities than those defined by the third criterion can be found elsewhere (Groves and Game 2016;Green and Grosholz 2021;Mill et al 2020;Dunham et al 2020;García-Díaz et al 2021).…”

“…We started by recognising that, when the target INNS cannot be eradicated, management plans should focus on addressing their negative and positive impacts (Lodge et al 2016 ; Dunham et al 2020 ; García-Díaz et al 2021 ). Unfortunately, the complexity and ambiguity often associated with impact assessments and management can limit the definition of priorities and targets to manage INNS impacts effectively.…”

Damming salmon fry: evidence for predation by non‐native warmwater fishes in reservoirs

“…Non-native species can have negative consequences for recipient ecosystems (Simberloff et al 2013), further imperiling threatened and endangered species (Clavero and Garc ıa-Berthou 2005) and potentially negating restoration improvements (Bellmore et al 2017). These risks are especially pronounced in freshwater systems, which are prone to high levels of invasion (Dunham et al 2020). Predation and competition by many non-native fish species have a high potential to negatively impact native fish communities (Woodford et al 2005, Kamerath et al 2008, Almeida et al 2012.…”