Contemporary perspectives on the ecological impacts of invasive freshwater fishes

Abstract

Introductions of non‐native freshwater fish continue to increase globally, although only a small proportion of these introductions will result in an invasion. These invasive populations can cause ecological impacts in the receiving ecosystem through processes including increased competition and predation pressure, genetic introgression and the transmission of non‐native pathogens. Definitions of ecological impact emphasize that shifts in the strength of these processes are insufficient for characterizing impact alone and, instead, must be associated with a quantifiable decline of biological and/or genetic diversity and lead to a measurable loss of diversity or change in ecosystem functioning. Assessments of ecological impact should thus consider the multiple processes and effects that potentially occur from invasive fish populations where, for example, impacts of invasive common carp Cyprinus carpio populations are through a combination of bottom‐up and top‐down processes that, in entirety, cause shifts in lake stable states and decreased species richness and/or abundances in the biotic communities. Such far‐reaching ecological impacts also align to contemporary definitions of ecosystem collapse, given they involve substantial and persistent declines in biodiversity and ecosystem functions that cannot be recovered unaided. Thus, while not all introduced freshwater fishes will become invasive, those species that do develop invasive populations can cause substantial ecological impacts, where some of the impacts on biodiversity and ecosystem functioning might be sufficiently harmful to be considered as contributing to ecosystem collapse.

Interactions of invasive pumpkinseed with a riverine endemic fish indicate trophic overlap but minimal consequences for somatic growth and condition

“…Although empirical evidence showed that non-native fishes can have detrimental ecological impact for native fishes and communities as a result of trophic interactions (Cucherousset and Olden, 2011;Britton, 2023), co-occurrence with nonnative pumpkinseed in the present study revealed no significant impact on chub growth and relative condition. In fact, a significant increase in growth but reduced condition was observed in both species in case of co-occurrence.…”

“…Detrimental impacts of non-native species on native species have been widely recognized and reported (Gozlan et al, 2010;Britton, 2023), mainly through processes such as increased predation and interspecific competition, but also through habitat modifications and interactions resulting in interference (Gozlan et al, 2010;Cucherousset and Olden, 2011;Almeida et al, 2014). In the literature, there is usually a bias to focus on the cases where high abundances of invaders occur, but this inherently results in high ecological impacts, which potentially overstates the ecological consequences of non-native species (Gozlan, 2008;Jackson et al, 2015).…”

“…Invasive species can cause wide ranging detrimental impacts in their receiving ecosystems, ranging from altered individual behaviours in native species through to alterations in ecosystem functioning (Cucherousset and Olden, 2011). Understanding the disruptions in processes, such predation and competition, caused by invasive species is important in determining the strength and direction of their impacts on native biodiversity (Tran et al, 2015;Britton, 2023) Consequently, an important first step in understanding the extent of the disruption to these processes is determining the extent of the trophic interactions of the invader with native species (Britton, 2018).…”

Identifying potential emerging invasive non‐native species from the freshwater pet trade

“…One species clearly highlighted as high‐risk by our native and global RR o and RR b metrics was C. auratus , which is consistent with its extensive invasion history in Germany, elsewhere in Europe and around the world. With impacts stemming from high feeding rates (Dickey et al, 2022), generalist diets (Monello & Wight, 2001; Richardson et al, 1995), disruptive foraging behaviour and genetic introgression with other Carassius species (Britton, 2022), there is evident need to curtail its risk through price or availability. Other highlighted species with extensive invasion histories that scored highly on at least one RR b and at least one RR o list include the fishes Ctenopharyngodon idella and Poecilia reticulata , and the snail Melanoides tuberculata .…”

The challenges faced by fish in a dynamic world

“…Two talks at the symposium, and papers in the special issue, deserve special note. The first, by Rob Britton (Britton, 2023), summarizes the impacts of introducing non-native freshwater fishes and, as such, an authoritative contribution to the subject. The second, by Josefin Sundin (Sundin, 2023), provides a fascinating overview of the recent ocean acidification controversy, highlighting the proliferation of influential studies purporting to show the reversal of predator avoidance behavior in CO 2 -exposed coral reef fish, which have ultimately proven problematic to replicate, and providing an indispensable case study for transparency and replicability in scientific publishing.…”