It is important for regulators and managers to effectively distinguish native from alien taxa. However, a taxon can have both native and alien populations within the same country as biogeographic and administrative boundaries do not always align. Here we propose a protocol for classifying populations as native, alien, cryptogenic, or native-alien, and describe the evidence required. This protocol comprises of three questions: (1) is the population outside the historic native range of the taxon, (2) is/was natural dispersal from the native range unlikely, and (3) is the taxon native to a part of the administrative region where the population is found. If information on introduction pathways, genetics, and biogeographical barriers is available, we propose an alternative process to answer question 2. The protocol was applied to 176 suspected native-alien populations in South Africa. A total of 132 populations from 77 native taxa were classified as native-alien, 13 as cryptogenic, 13 as alien (native-alien status uncertain), and 18 as native. We believe the protocol provides a transparent and standardised method for categorising native-alien populations and thereby facilitates the appropriate regulation and management of this type of biological invasion.

Non-indigenous species have been widely recognized as major drivers of biodiversity loss. However, management in marine ecosystems entails particular challenges of detection and control, with an approach which requires stakeholders from the government, academia and the public. To generate a first approach to what should be the national Chilean agenda for non-indigenous species (NIS) management, a workshop was convened at the Universidad Católica del Norte in Coquimbo on the past, present and future of marine bioinvasions in Chile. The workshop, with more than 60 participants, including academics and public services, gathered information from the published literature on the state of the art of marine bioinvasions in Chile and proposed a work agenda for the coming years. The results highlight that the design and implementation of more focused and effective management policies and programs will be required to potentially reduce the rates of new invasions and identify mitigation strategies. We present the first proposed NIS research and management agenda for Chile developed through a collaborative process between researchers and the Chilean government, with a joint vision of both the challenges and solutions.

In July 2019 an established infestation of Pheidole fervens was detected in Australia for the first time. An eradication program was conducted, and by November 2022 the ant had not been detected for 31 months so it was declared eradicated. This is the first time an exotic ant species has been eradicated from within Australia without other infestations of the same species being found in the meantime. Much of the achievement can be attributed to early detection of the incursion by Australia’s National Border Surveillance program.

Invasive alien species (IAS), including aquatic invasive alien rodents (AIAR), cause extensive damage to ecosystems with significant economic, human health, and environmental concerns. In France, AIAR populations are well established, and a permanent control programme has been set up in several areas to reduce their impact. While some studies have reported the results of AIAR control activities, detailed information on current management strategies and how control activities are implemented in the field is lacking. This study evaluates the implementation of the management plan and control activities of AIAR in France regarding (i) problem definition, feasibility and objectives, (ii) planning from action plan, organization, funding and methods, (iii) field implementation from spatial prioritisation and personnel and (iv) monitoring and evaluation. Our study reveals that in France, (i) local and regional institutions mainly manage control activities primarily through volunteers and (ii) national and regional management plans on AIAR controls are missing. We elaborate on several actions that can help local and regional entities in improving their control programme, including zonation for priority actions, development of performance indicators of control activities, engagement of volunteers, and scientific monitoring of AIAR populations.

Interception data of insects collected at quarantine borders across China were cross-checked with incursion data from 2003 to 2016. In total, 83,983 insect interceptions were recorded across quarantine borders, involving 1,458 insect species. The species interception index at the family level was calculated to make each insect family comparable. Among the intercepted families, eight families that harm woody plants were intercepted at a high frequency, of which Noctuidae was the most intercepted family. In contrast, seventeen families that harm non-woody plants had a high interception frequency, of which the Silvanidae had the highest species interception frequency. Among the 1,458 intercepted insect species, 147 species were included in a list of quarantine insects in China. In terms of insect species, thirteen species had a high interception frequency (intercepted > 100 times or the cumulative yearly interception ≥ 10 years), accounting for 90.1% of the total interceptions. Among these 13 species, ten species have become established in mainland China, with eight species specifically harmful to woody plants. Looking at the extent of insect pest interceptions, corresponding control measures should be initiated to minimize impacts to natural forests. These results show that border quarantine surveys can help identify and target control measures against invasive alien species. Still, the current quarantine system needs further improvement to successfully prevent alien species from crossing the border and spreading in natural areas.

Callinina georgiana (banded mystery snail) and Cipangopaludina japonica (Japanese mystery snail) are two exotic viviparid snail species that have been introduced to North America. These snail species harbor parasites, predate on the eggs of native fish fauna and are prolific in their ability to spread across various freshwater environments. While several recent studies have explored the population structure and range expansion of the species in the United States, none have formally addressed control or eradication strategies. In this study, we attempted to do this by carrying out a series of assays to determine the efficacy of the popular molluscicide, niclosamide monohydrate against both species under both acute and chronic exposure. Our results show that the lethal dose required to achieve 50 % mortality (LD₅₀) for C. georgiana and C. japonica was 1.509 mg/L and 1.296 mg/L respectively. In acute exposure experiments we observed that at higher concentrations, all C. georgiana specimens in experimental treatment tanks were dead but C. japonica never reached 100% mortality even at the highest concentration. In chronic exposure experiments, C. georgiana did not survive more than a week while C. japonica did not survive more than 11 days in the experimental tanks. We conclude that niclosamide is an effective chemical control agent for eradication of invasive mystery snails in North America. However, further studies exploring the effect of the molluscide on non-target species, especially local native fauna, should be investigated prior to any scaled up field applications.

A bench-scale dose-response study evaluated the efficacy of a commercially available copper-based molluscicide known as EarthTec QZ for controlling quagga veligers collected from three Southern California sites impacted by quagga mussels. A variety of concentrations were tested (0, 3, 16.7, 33.4, and 50.1 µL/L of EarthTec QZ or 0, 0.18, 1.0, 2.0, 3.0 mg/L as copper (Cu), respectively) for different durations (0.5, 2, 5, and 24 hours) on quagga mussel veligers. Water from each study site was also used in non-target 96-hour acute toxicity testing of three other species. A suite of water quality parameters was measured to characterize the differences between the study sites. The federal and California secondary maximum contaminant level and action level for copper in drinking water are 1.0 and 1.3 mg/L as Cu, respectively; therefore, results for the 16.7 µL/L EarthTec QZ (1.0 mg/L as Cu) test condition were the main reference point for assessing the efficacy of EarthTec QZ as a feasible treatment strategy. Under this condition, veliger mortality at two study sites, Lake Mathews, and a downstream water treatment plant, was found to be greater than 60% and 85% after 5 hours, and 95% and 100% after 24 hours, respectively. Lower efficacy was observed for the Lake Piru study site, with approximately 30% veliger mortality after 24 hours. Alkalinity, dissolved organic carbon, and chemical oxygen demand were found to be significant variables for veliger mortality in these hard water locations based on linear regression modeling. The three non-target indicator species were adversely affected by EarthTec QZ at concentrations tested. These results indicate that this product has potential as an effective chemical control agent against quagga veligers at low doses, but the aforementioned water quality parameters must be considered with full-scale application to optimize target efficacy, while minimizing exposure to non-target species and costs.

Zebra (Dreissena polymorpha Pallas, 1771) and quagga (Dreissena rostriformis bugensis Andrusov, 1897) mussels are important pests in North America and Europe, where they cause costly economic damage to water infrastructure and severe environmental impacts to lake ecosystems. Strategies for combating these invasive mussels do not differentiate between the species, and little is known about how they may differ in terms of their susceptibility to chemical control methods. In this study, adult zebra and quagga mussels were collected from Lake Ontario and exposed to three different concentrations of EarthTec QZ – 60, 120, and 180 μg/L as liquid ionic copper – until 100% mortality was reached. Quagga mussels died significantly faster and at lower doses of copper ion than zebra mussels. Dry tissue collected from the mollusks at the time of death was analyzed for the copper concentration in each species and results revealed that zebra mussels accumulated and were able to tolerate much higher concentrations of copper in their tissues than quagga mussels. After 10 days’ exposure to the highest dose rate (180 μg/L) zebra mussels had experienced less than 20% mortality while accumulating more than 1,000 mg/kg copper, whereas the quagga mussels treated at the same 180 ug/L suffered 100% mortality after 10 days despite having accumulated only 300 mg/kg of copper. While more research is needed to explain the precise mechanisms whereby zebra mussels are able to tolerate the much higher bodily concentrations of copper than quagga mussels, these results have direct management implications when copper is used for dreissenid control.

The red swamp crayfish Procambarus clarkii is native to the southeast United States but has successfully invaded nearly every continent around the world. Although physical, biological, and chemical controls are employed to reduce or eliminate populations in open-water systems, terrestrial burrows provide a potential refuge from aquatic control treatments. We conducted burrow trials to test whether two physical blocker treatments would kill P. clarkii in their burrows. Bentonite clay (a sealing agent) and expanding foam (an insulating sealant) were each applied to 37 crayfish burrows, and 36 burrows served as treatment controls (i.e., 110 total burrows). Burrows were excavated 48 hr after the application of the physical blockers to assess the status of crayfish in treated and control burrows. There was 74% mortality of crayfish in occupied burrows treated with bentonite clay, 62% in burrows treated with expanding foam, and 6% mortality in control burrows. We believe bentonite clay should continue to be field-tested; however, because expanding foam is toxic to aquatic organisms and is expected to persist in the environment, we do not believe it is a suitable physical blocker for the control of invasive crayfish in burrows. Bentonite clay applications likely will not need permits, will mitigate damage to banks and levees caused by burrowing crayfish, and can be used with other control agents such as pesticides. However, the use of physical blockers may be limited at field sites that have burrows with complex morphologies. We believe the use of bentonite clay to control invasive crayfish in terrestrial burrows will provide resource managers with an effective tool for their integrative pest management programs.

The round goby (Neogobius melanostomus) invaded the Great Lakes in the 1990s and the species continued expansion into inland bodies of water, raising basin wide concerns for negative ecological impacts. The Lower Fox River (LFR), Wisconsin, USA, is the state’s largest tributary linking the Great Lakes to inland Lake Winnebago through a fragmented waterway of eight lock and dam structures across 62.0 river kilometers (RKm). Round goby were detected in the LFR lower river reaches, in the early 2000’s below an invasive species barrier (completely sealed structure) located near the midpoint of the LFR (RKm 31.5), but in 2015, the species was observed above the barrier raising concerns for upstream invasion. This discovery prompted the closure of the upper most navigational lock system (Menasha Lock, RKm 62.0) separating the outflow of Lake Winnebago to the LFR. The goal of this study was to assess the distribution and abundance of round goby throughout the entire LFR in 2019–2021 using baited minnow traps. We further evaluate differences in capture rates between combinations of minnow trap styles, bait types, and bait quantities. A total of 1,007 round goby were captured during monitoring surveys throughout the LFR (2019–2021), confirming presence in all river segments with maximum upstream extent reaching Menasha Lock. Highest densities of round goby are found below the invasive species barrier (RKm 31.5), but males and females are present at the current maximum upstream distribution. An additional 834 round goby were captured during the comparison of trapping strategies and suggest round-style minnow traps baited with food (i.e., dog food or hotdog) are successful in capturing round goby and outperform other trap/bait types. Continued monitoring would help describe trends in abundance and adaptive sampling approaches will improve detection.

Invasive fish can profoundly affect communities they invade. In Hawai‘i, invasive fishes have become established in many anchialine pools, threatening the persistence of resident invertebrates, including several endangered species. Tools to eradicate invasive fishes from these pools are lacking. This study tested the efficacy of carbon dioxide (CO₂) gas diffused into anchialine pool water as a method to eradicate invasive Mozambique tilapia (Oreochromis mossambicus), guppies (Poecilia reticulata), and western mosquitofish (Gambusia affinis). We first conducted aquarium trials to identify how these fishes were affected by elevated CO₂ and the concomitant reduction in pH. We then carried out field trials in pools containing these fish in one pool each at two national historical parks on the Island of Hawai‘i during July 2021–January 2022. We also developed environmental DNA (eDNA) protocols to detect fish that may have survived CO₂ treatments. The effect of CO₂ on fish behavior varied among species; at pH 5.3 (CO₂ = 255 mg/L) for tilapia and 5.0 (CO₂ = 488 mg/L) for tilapia, guppies, and mosquitofish, all generally lost their ability to swim, showed slow or no gill movement, and altered their position in the water column. No tilapia survived the trials (n = 4 and 6 individuals at pH 5.3 and 5.0, respectively). In contrast, 41.7% (n = 12) of adult guppies and 66.7% (n = 12) of adult mosquitofish survived treatment at pH 5.0. In the field we were unable to reduce anchialine pool water pH below 5.7. Regardless, we were able to eradicate tilapia from one pool over four sequential treatments. Post-treatment eDNA assessments supported visual surveys, confirming our results. We were not able to eradicate guppies and mosquitofish. Results from this study show that CO₂ can be an effective tool for eradicating invasive tilapia from anchialine pools, and post-treatment eDNA assessments can provide managers with a method for evaluating the success of eradication efforts.

We conducted research to develop a safe and effective toxic bait to control the small Indian mongoose (Urva auropunctata), an invasive vertebrate predator impacting the survival of native species in Hawai‘i and in other parts of the world. A preserved fish-based bait product was found to be highly palatable to mongooses in cage trials and subsequent formulations with diphacinone (0.005%) showed promise as an efficacious toxic bait for mongooses. This product is intended for future use to control mongooses in conservation and urban areas, and as a biosecurity tool at ports of entry to address accidental introductions into mongoose-free areas. Anticipated delivery of this toxic bait is in tamper-proof bait stations. We designed three prototype bait stations constructed with polyvinyl chloride (PVC) drainage pipes and evaluated their performance in enclosure trials with wild-caught mongooses and in field trials with free-ranging mongooses. A commercially available tamper-resistant rodenticide bait station was also used for comparison to the prototypes in our trials. The goal was to develop a bait station that is readily used by mongooses, allows for bait consumption in place, prevents removal of bait, and restricts access to nontarget animals. We used a non-toxic formulation of the fish-based bait product and monitored bait station use, visitation rates, bait uptake, and spillage. All four bait station types were used by mongooses in the laboratory, and one PVC bait station design and the commercial bait station exhibited multiple mongoose visitations with minimal bait spillage in the field. We did not record any significant nontarget species interactions with the bait during the field trials. The PVC bait station design and commercial bait station are approved methods of bait delivery in the subsequent field efficacy trials under an Experimental Use Permit for the upcoming registration of “Fish-based Bait for Mongooses” with the Environmental Protection Agency.