Untitled

Abstract

Predicting the ecological impacts of invasive fishes is crucial for understanding their risks in the environment. Experimental approaches that provide empirical data on invasion impacts provide both theoretical insights and data of high management utility for prioritising high-risk invaders. Here, a synthesis of some experimental approaches that predict invasion impacts of non-native fish is presented, where the focus is on impacts relating to the trophic impacts of the invader on either native trophically analogous fishes or prey populations. Experiments in tank aquaria are advantageous in providing homogenous and controlled conditions that also enable high replication. Competition-based studies can determine invasion impacts via exposure of fish to fixed food rations, although these experiments tend to produce results in intensely competitive conditions that might not occur in the wild. Comparative functional response experiments in tank aquaria have been successfully applied to determining the relative impacts of invaders compared with native species on prey populations, and have revealed high resource efficiency in globally invasive piscivorous fishes. Experiments completed in mesocosms and small ponds have the advantage of providing replicated systems in semi-natural conditions. They have been successful in revealing that rather than competing with native fishes, many invasive fishes show strong patterns of trophic niche partitioning. These patterns are also evident in these fishes when in natural invaded communities. Thus, whilst it is often suggested invasion impacts from non-native fishes result from inter-specific competition, evidence for this from experimental and field-based predictions is equivocal.

Predicting the ecological impacts of an alien invader: Experimental approaches reveal the trophic consequences of competition

“…Manipulating the abundances of alien and native species enables the outcomes of the altered strength of their competitive interactions to be measured (Britton, 2018). Manipulating the abundances of alien and native species enables the outcomes of the altered strength of their competitive interactions to be measured (Britton, 2018).…”

“…For example, cohabitation pond mesocosm experiments can compare the results of interspecific competition between sympatric alien and native fishes versus allopatric treatments involving only intraspecific competition (Britton, 2018). The competitive relationships between the species can then be informed by aquaria experiments (Britton, 2018). The competitive relationships between the species can then be informed by aquaria experiments (Britton, 2018).…”

“…Across taxa, it remains equivocal as to how these potential shifts in the trophic niches of native species manifest following an invasion (Britton et al, 2018) and so can be investigated further using empirical experiments. Manipulating the abundances of alien and native species enables the outcomes of the altered strength of their competitive interactions to be measured (Britton, 2018). For example, cohabitation pond mesocosm experiments can compare the results of interspecific competition between sympatric alien and native fishes versus allopatric treatments involving only intraspecific competition (Britton, 2018).…”

Competition between Invasive Ruffe (Gymnocephalus cernua) and Native Yellow Perch (Perca flavescens) in Experimental Mesocosms

“…Competitive interactions are one vehicle for adverse effects of invasive species [31,32], however, the relative importance interspecific completion is unclear, and results of small-scale experiments may not translate to larger scales [33,34]. Relatively few studies have provided experimental evidence of competition between fishes at larger scales.…”

Predicting the competitive interactions and trophic niche consequences of a globally invasive fish with threatened native species

“…Laverty et al, 2017;Paterson et al, 2015). However, a potential issue of CFRs is their experimental designs, where exposing consumer species to single prey species within tank aquaria can represent an over-simplification of more complex natural systems in which a wider range of prey resources are available (Britton, 2018;Dick et al, 2014). Scaling-up experimental approaches for predicting the trophic impacts of alien freshwater fishes to mesocosms and pond enclosures have provided considerable insights into their trophic interactions with native species (Britton, 2018), with suggestions that rather than share and potentially compete for similar prey resources, functionally analogous native and alien fishes often demonstrate strong patterns of trophic niche partitioning (Britton et al, 2018;Raby et al, 2020).…”