The effectiveness of non-native fish removal techniques in freshwater ecosystems: a systematic review

Abstract

In aquatic systems, biological invasions can result in adverse ecological effects. Management techniques available for non-native fish removal programs (including eradication and population size control) vary widely, but include chemicals, harvest regimes, physical removal, or biological control. For management agencies, deciding on what non-native fish removal program to use has been challenging because there is little reliable information about the relative effectiveness of these measures in controlling or eradicating non-native fish. We conducted a systematic review, including a critical appraisal of study validity, to assess the effectiveness of different non-native fish removal methods and to identify the factors that influence the overall success rate of each type of method. We found 95 relevant studies, generating 158 data sets. The evidence base was dominated by poorly documented studies with inadequate experimental designs (76% of removal projects). When the management goal was non-native fish eradication, chemical treatments were relatively successful (antimycin 89%; rotenone 75%) compared with other interventions. Electrofishing and passive removal measure studies indicated successful eradication was possible (58% each) but required intensive effort and multiple treatments over a number of years. Of these studies with sufficient information, electrofishing had the highest success for population size control (56% of data sets). Overall, inadequate data quality and completeness severely limited our ability to make strong conclusions about the relationships between non-native fish abundance and different methods of eradication and population control and the factors influencing the overall success rate of each method. Our review highlights that there is considerable scope for improving our evaluations of non-native fish removal methods. It is recommended that programs should have explicitly stated objectives, better data reporting, and study designs that (when possible and appropriate) incorporate replicated and controlled investigations with rigorous, long-term quantitative monitoring. Future research on the effectiveness of non-native fish removal methods should focus on: (i) the efficacy of existing or potentially new removal measures in larger, more complex environments; (ii) a broader range of removal measures in general; and (iii) phenotypic characteristics of individual fish within a population that fail to be eradicated or controlled.

What to do when invaders are out of control?

“…There were not enough cases for any given species (range of 0-5) to draw definitive conclusions about any individual species. Although our findings may not be directly comparable to Rytwinski et al (2018), the percentage of successful eradications for the case of these eight species is considerably lower (10% vs. up to 89%). Lower success rates for eradication were expected for this subset of unusually successful invaders.…”

“…Given this, we did not focus on prevention and instead focused on a literature review to better understand how these eight invaders have been controlled via conventional eradication efforts (Supplements 1-3, Supporting information). Recently, Rytwinski et al (2018) conducted a systematic review of freshwater fish eradications, which included the eight species considered here. Of the studies they considered, eradication through nonselective piscicides was highly effective (75 and 89% for antimycin and rotenone, respectively).…”

Scientists' warning on invasive alien species

“…Each invasion has a unique context that determines appropriate management or eradication targets, but projects, methods, and success rates have recently been summarized for several groups, including terrestrial vertebrates on islands (DIISE Partners, 2014), insects and plant pathogens (Kean et al ., 2017), crayfish (Stebbing, Longshaw, & Scott, 2014), and freshwater fishes (Rytwinski et al ., 2019). This has allowed overviews and syntheses of conditions likely to result in success by particular means (e.g.…”

Remarkable response of native fishes to invasive trout suppression varies with trout density, temperature, and annual hydrology

“…Further, temporal variability in flow, turbidity, and temperature, which may mediate competition, predation, and other biotic interactions (Yard et al 2011;Ward and Morton-Starner 2015;Ward et al 2016), may also confound interpretation of population trends in native and invasive fishes following suppression (Coggins et al 2011;Propst et al 2015). Thus, conservation of native fishes would benefit from improved understanding of the ecological impact of species invasions in the context of environmental variability (Cucherousset and Olden 2011), how patterns of distribution and abundance of native fishes relate to those of invasive fishes, and how native fishes will respond to invasive species suppression under different environmental conditions (Rytwinski et al 2019).…”