Stopping invasive species early in the invasion process has the potential to save hundreds of billions of dollars and avert damage to agriculture, natural areas, and human health. While urban areas pose particular challenges to early detection, they also present special opportunities. Urban areas and their ports of entry host higher concentrations of invasive species and, with increasing travel and transport, the number of species introduced to urban areas will increase. Along with many invasive species, urban areas contain many citizens interested in being citizen scientists and the potential for taxonomic experts to be associated with major institutions of learning. Early detection is an effective strategy and citizen scientists are effective data collectors. We present a model called Invader Detectives that harnesses existing data collection by citizen scientists to support early detection of invasive species in urban areas. The data-driven approach is being implemented as a pilot project in the metropolitan Washington DC area but we hope to find partners in urban areas across the country to create a nation-wide network of Invader Detective chapters. The Invader Detectives structure is reviewed and lessons learned are reported.

Parthenium, Parthenium hysterophorus L. poses a serious environmental and socio-economic threat in Pakistan. It was identified as a priority for control in Pakistan and an integrated control programme has been launched against this invasive weed. In 2009 the biological control agent, Zygogramma bicolorata Pallister, was documented in Pakistan and thought to have naturally dispersed into the region. Despite the presence of this biological control agent for the past decade in Pakistan, the population level impact on parthenium weed has been limited by several factors, including climate, diapause and limited dispersal. A redistribution programme was initiated to promote this biological control agent in Pakistan. In addition to this, the parthenium winter rust, Puccinia abrupta Diet. & Holw. var. partheniicola (Jackson) Parmelee, was reported in Pakistan for the first time in 2019. Despite this rust being widespread there appears to be limited impact, most likely linked to environmental conditions and the timing of infection. Monitoring programmes for this rust have been initiated for the winter of 2020. CABI, through its Action on Invasives programme, has established a quarantine facility for the screening of complementary biological control agents not yet in Pakistan against parthenium and other invasive weeds in the country. With this quarantine facility the importation of the stem boring weevil, Listronotus setosipennis (Hustache) was possible and host range testing is underway. The biological control of parthenium in Pakistan is still at an early stage, and considerable effort is required to fill the management toolbox for this invasive weed.

Previous papers discussing the effectiveness of injurious wildlife listings under 18 U.S.C. 42(a) of the Lacey Act have emphasized failures while ignoring the many successes. We looked at the 120-year history of injurious listing and then determined the effectiveness of the listings since the U.S. Fish and Wildlife Service (USFWS) gained the listing authority in 1940. We measured success by the effectiveness of listing relative to the stage of the invasion process – that is, whether or not a species was established at the time of listing, if it since established, and if it subsequently spread to other States. The USFWS started listing preemptively with its first rule in 1952 and has added the majority of species preemptively since then. We analyzed the 307 species that were listed for invasiveness (excluding species listed for other injurious reasons). Of those species, 288 (94%) were listed preemptively (before they became established). Although we acknowledge that other factors may play a role, we consider species that were listed before establishment and remained not established as “very effective” listings. All 288 remained not established – a 100% prevention rate when listed preemptively. Only 19 of the 307 species (6%) were listed after establishment, and they remain established. The listings are considered “effective” for the 4% that remained within the State(s) they were established in at listing and “ineffective” or “not applicable” for the 2% that spread to other States. The rationale for listing established species is explained herein. We conclude that injurious species listings can be effective at any stage, but prohibiting the importation into the United States of high-risk species prior to their introduction and establishment into U.S. environments is very effective in preventing invasions, and this success has heretofore been overlooked.

The inconsistency in regulated species lists across the shared waters of the Great Lakes undermines the collective prevention efforts of the region, resulting in a “weakest link” problem; some jurisdictions regulate more than 100 species, others fewer than 20. We examine progress over the last twelve years toward more consistent regulated species lists within the 10 Great Lakes jurisdictions. Using a risk assessment framework, we assess a suite of regulated and unregulated organisms that have been identified as having the potential for introduction. Using these species assessments, we determine how sufficient current regulated species lists are in protecting against high-risk species. We also use these species assessments to transparently identify potential high-risk candidates for regional regulatory consideration. A total of 136 aquatic species were regulated by at least one jurisdiction (69 plant species and 67 animal species). The number of species regulated by 5 or more jurisdictions has gone from 10 in 2008 to 44 in 2020. However, the majority (68%) of the currently regulated species are listed in less than half of the Great Lakes jurisdictions. The number of regulated species varies widely across jurisdictions for both taxonomic groups. Wisconsin regulates the largest number of plant and animal species (104 in total), followed by Minnesota (71), New York (59), Illinois/Indiana/Michigan/Ohio (45), Pennsylvania (34), Ontario (23) and Québec (19). We observed only a weak positive correlation between impact score and regulation status. Many of the most-regulated species have impact scores in the low or low-moderate categories, and several species with high impact scores are regulated by less than half of jurisdictions. Twenty-one species (17 plant and 4 animal) are identified as priorities for future regulatory listing.

The American charru mussel Mytella strigata (Hanley, 1843) is an invasive species of great concern along the shores of North America and Asia. As with most invasive mussels, it is very difficult to eradicate once established. Surveillance therefore plays a vital role in controlling its spread. Molecular tools like environmental DNA (eDNA) have proved to be useful in recent years to assist in the early detection and management of invasive species, with considerable advantages over conventional methods like substrate monitoring and sampling, which can be relatively laborious and time-intensive. This technique can be particularly useful in the initial stages of invasion when the population density is often too low to be detected by visual surveys alone. In the present study, we developed a species-specific quantitative polymerase chain reaction (qPCR) approach targeting a cytochrome c oxidase subunit I (COI) DNA fragment aimed at detecting the presence of M. strigata from water samples. We also investigated the relationship between mussel cover and eDNA concentration. Our approach was tested on coastal seawater samples from 14 sites in Singapore, supported by conventional visual quadrat surveys. The results showed clear, positive M. strigata eDNA detection for all sites where this species was observed visually during field surveys. However, there was a weakly negative correlation between percent mussel cover and eDNA concentration, indicating that mussel abundance could not be estimated reliably using seawater eDNA alone. Nevertheless, this study underscores the effectiveness of eDNA in informing the presence and distribution of M. strigata along extensive coastlines comprising different habitats. This approach contributes to a robust toolkit for routine surveillance at sites where invasion may be impending to control the spread of the invasive mussel.

To reduce the transport of potentially invasive species on ships’ submerged surfaces, rapid—and accurate—estimates of biofouling are needed so shipowners and regulators can effectively assess and manage biofouling. This pilot study developed a model approach for that task. First, photographic images were collected in situ with a submersible, inexpensive pocket camera. These images were used to develop image processing algorithms and train machine learning models to classify images containing natural assemblages of fouling organisms. All of the algorithms and models were implemented in a widely available software package (MATLAB©). Initially, an unsupervised clustering model was used, and three types of fouling were delineated. Using a supervised classification approach, however, seven types of fouling could be identified. In this manner, fouling was successfully quantified over time on experimental panels immersed in seawater. This work provides a model for the easy, quick, and cost-effective classification of biofouling.

The inadvertent movement of non-indigenous species (NIS) poses a significant risk to marine ecosystems. The present study examined the interactive effects of pressure-washing intensity and duration on removal of biofouling and various mobile invertebrate species on string-cultured Pacific oysters (Crassostrea gigas (Thunberg, 1793)). Six pressure-washing treatments were established by combining two intensities (2000 and 3000 PSI) and three durations (10, 20, and 30 s). These were compared with controls of no washing and simple dunking, which most likely are the current industry practices. Oysters in the various pressure-washing treatments had significantly less total biofouling compared to the no-washing and dunk controls. Significantly less biofouling remained when pressure washing was applied for longer periods of time (20 and 30 s) than for shorter periods (10 s), regardless of intensity. Dunking oysters repeatedly in seawater had no significant effect on the amount of biofouling when compared with the no-wash control, although it did lead to significantly fewer shrimp. Regardless of the faunal group assessed (i.e. total biofouling community, NIS tunicates, or various mobile invertebrate species), individuals remained on the oysters after every experimental washing treatment, suggesting none are 100% effective. In addition, the number of oysters remaining on the strings and their shell condition were significantly reduced after pressure washing, suggesting a potential cost to growers. The results have implications both for oyster farming and mitigation of NIS movement.

The common myna was first recorded in Jordan in 2010, in the Jordan Valley just north of the Dead Sea, as a result of secondary expansion of an invasive population from a neighboring country. After initial establishment, it rapidly spread throughout many parts of the country. This included apparent jump dispersals of 20–60 km to towns located in the desert along highways. The common myna is thus able to become fully invasive in arid and semi-arid environments under the influence of human factors. The results of a Maxent model trained with data from the invaded region (the southern Levant) and the native range suggest that the common myna’s expansion and current distribution is driven mainly by anthropogenic factors rather than climatic variables. This study provides a nationwide baseline about the distribution of the invasive common myna, and potential for further spread as a baseline for monitoring and prioritizing actions to control spread and impacts. The rapid expansion of common myna in Jordan, which is apparently enhanced by the influx of dispersing birds from neighboring countries, necessitates more attention and urgent action and coordination at various levels.

Signal crayfish (Pacifastacus leniusculus) is a freshwater crayfish, originally from the west coast of North America. It is now widespread in Europe and it is listed as a harmful species in the list of invasive species of European Union concern. We tested the effect of LED lights in signal crayfish trapping in a large Finnish lake. Light attraction could be a cost-effective way of increasing crayfish catches in eradication programs and commercial trapping, but research results are largely lacking. Experiments were conducted in Lake Päijänne which has an abundant population of invasive signal crayfish. We tested whether white and green LED lights attached inside the baited traps increase crayfish catch per unit effort (CPUE) compared with baited traps without light. Mean CPUE was higher in traps only baited with a fish (2.7 ind. 24 h^-1) compared to traps with a fish bait and a green LED light (1.5 ind. 24 h^-1), and traps with a fish bait and a white LED light (1.9 ind. 24 h^-1). Our results show that LED lights did not increase signal crayfish CPUE. Instead, lower catches in traps with LED lights indicate that crayfish were not attracted by the light. We observed significant variation in CPUEs, but without interaction between crayfish sex or size and light treatments. We conclude that LED lights do not increase the effectiveness of signal crayfish trapping.

Aquatic invasions are a major ecological and socio-economic concern. Management of invasive aquatic populations requires a robust understanding of the effectiveness and suitability of control methods. In this review, we consider multiple control options for the management of invasive aquatic amphipods, exploring their efficacy and application constraints. Technological opportunities (pheromone, RNAi, biotechnologies) and gaps in our understanding around control mechanisms are identified, with the aim to improve management success of this order. Within this review, the UK invasion of the killer shrimp, Dikerogammarus villosus (Sowinsky, 1894) is used as a case study of the best explored example of invasive amphipod control. This species has had a range of ecological, physiological, pathological, and experimental research conducted upon it, which is highlighted from a management perspective. This same data, where available, has been synthesised for 46 other invasive amphipods, to probe for weaknesses that future management methods can exploit and be developed around. Successful management examples for invasive amphipod species remain rare. A lack of currently available tested options severely limits the possibility for amphipod management, post establishment. For future management to be successful, further work is needed to develop targeted and specific control methods, which ideally, are cost effective, have no/little associated ecological impacts, and can be broadly applied in closed and open water systems. Our synthesis presents opportunities for the further, informed development of control systems for invasive amphipods.

Removing invasive rats from island ecosystems using rodenticides has proven conservation benefits and is an important management tool for conserving and restoring island ecosystems. However, rodenticide-based eradications can fail if not all rats consume enough bait to result in lethal toxicosis. A recent post-operational review of a failed attempt to eradicate rats from Wake Atoll suggested that some individuals may not have ingested a lethal dose of rodenticide due to potential dietary and/or sensory preferences developed via regular access to anthropogenic food sources. These food sources may be higher in fats and oils, possessing different sensory properties (e.g., softer, chewier, etc.) than the harder pellet formulation of the rodenticide Brodifacoum 25W Conservation (B-25W) used in the eradication attempt. To test this theory, we captured rats from two areas on Wake Island where they may have regular access to human food sources, as well as an uninhabited part of island where rats presumably have less access to human-based food sources and therefore are less likely to be preconditioned for these food types. We subjected them to a head-to-head two-choice bait selection trial between a “soft” sachet formulation of a brodifacoum-based bait, FINAL Soft Bait with Lumitrack® (FINAL), versus the harder pellet formulation of B-25W. Regardless of which habitat rats were captured in, rats overwhelmingly preferred the pellet formulation. No rats in the head-to-head trail consumed any of the FINAL bait, and 100% of the rats that consumed B-25W died. Of the rats in a separate no-choice trail of just FINAL bait, 5 failed to eat any bait; of the rats that did consume some of the FINAL bait, 80% died. Our results demonstrate that Polynesian rats on Wake Atoll do not prefer this soft formulation of brodifacoum-based rodenticide bait. O ur results suggest that baiting strategies in the inhabited regions of the atoll, for a proposed eradication attempt, should continue to focus on utilizing traditional pellet formulations. While these results are unequivocal in our test case, we suggest caution in making inference to other situations where dietary preferences of local rodent populations may differ, and local environmental conditions may make other baiting choices more appropriate and efficacious.

Introduced common mynas (Acridotheres tristis) can negatively impact native wildlife throughout the mynas’ non-indigenous range, and in Seychelles myna eradications have been attempted on some smaller islands to protect endemic and indigenous fauna. Initial attempts, relying on a quick knock-down of the population using toxicants, failed. Here we describe an eradication on North Island, Seychelles, that was accomplished by trapping, supported by shooting in the final stages. This eradication attempt was ultimately successful but took place in two stages spanning seven years and involved removing 1641 birds. During the second, successful, stage, morphometric data collected from caught mynas provided pointers to optimum times during the mynas’ annual cycle to target control activities. During both stages the trapping of non-target species interfered with the capture of mynas. The six main conclusions from this eradication are (i) eradication of mynas from small islands is feasible and achievable by trapping and shooting, without recourse to the use of toxicants; (ii) provision of adequate resources for the life of an eradication attempt, especially ensuring continuity of funding and staffing, is essential for the efficient removal of the whole population; (iii) knowledge of myna phenology can be used to target the optimal timing of an eradication attempt, (iv) post eradication, vigilance and capacity for immediate action must be maintained to remove any immigrant mynas, (v) further research on trap design is needed to minimise the capture of non-target species, and (vi) introduced endemic bird populations should be monitored to assess their responses to myna removal.

Given the status of the African clawed frog Xenopus laevis as a global amphibian invader, and the potential spread of its invasive populations in Europe and other continents, it is essential to identify the environmental factors and methods that maximize the trapping output of control actions. Cost-effective methods should maximize the number of trapped individuals, and preferably the number of females. We tested five types of attractants in traps, split into two categories: playbacks and conspecific lures, and compared their efficiency in terms of number of trapped individuals (total, females, and males) against the control method currently in use in France (use of food bait). We also estimated the influence of moonlight, an environmental factor known to affect amphibian activity. Playback methods did not increase the capture probability for either sex. In contrast, using a female as a lure allowed us to trap both more individuals (224% compared to the control), more females (186%) and more males (190%), whereas using a male only allowed us to trap more males (167%). These effects were stronger under low moonlight intensity, and at the end of the breeding season. Using female lures appeared to be the best method, both due to a higher number of trapped individuals and a higher number of trapped females. Our study also emphasizes the need for considering the influence of the lunar cycle when planning fieldwork to optimize the cost-efficiency of control actions. We recommend to preferentially set traps under low moonlight intensities.

In 2017 and 2018, California and New Zealand introduced new regulatory regimes for the maritime shipping industry by implementing and enforcing regulations for biofouling management. Both sets of regulations reflect the principles of the International Maritime Organization’s Biofouling Guidelines and are designed to encourage proactive biofouling management to reduce the likelihood of nonindigenous species introductions. During the first year of enforcement, maritime shipping vessels that were subject to the respective regulations made similar numbers of arrivals at California (2,515) and New Zealand (2,556) ports. California and New Zealand regulators also conducted similar numbers of biofouling inspections during this time: 505 in California and 498 in New Zealand. Most instances of noncompliance in both jurisdictions were a result of incomplete understanding of these new regulations, however provisions to provide flexibility and education ensured the maritime shipping industry had opportunities to learn about the requirements, improve compliance, and reduce learning curves. An important lesson learned for both jurisdictions was the importance of extensive and targeted outreach to the various stakeholder groups that play a role in achieving compliance and effective risk reduction. The lessons learned and noncompliance trends identified during the first year of inspections in California and New Zealand provide valuable insights for consideration in light of the current review of the IMO Biofouling Guidelines and moves to develop biofouling requirements in other jurisdictions.

Invasive species surveillance programs can utilize environmental DNA sampling and analysis to provide information on the presence of invasive species. Wider utilization of eDNA techniques for invasive species surveillance may be warranted. This paper covers topics directed towards invasive species managers and eDNA practitioners working at the intersection of eDNA techniques and invasive species surveillance. It provides background information on the utility of eDNA for invasive species management and points to various examples of its use across federal and international programs. It provides information on 1) why an invasive species manager should consider using eDNA, 2) deciding if eDNA can help with the manager’s surveillance needs, 3) important components to operational implementation, and 4) a high-level overview of the technical steps necessary for eDNA analysis. The goal of this paper is to assist invasive species managers in deciding if, when, and how to use eDNA for surveillance. If eDNA use is elected, the paper provides guidance on steps to ensure a clear understanding of the strengths and limitation of the methods and how results can be best utilized in the context of invasive species surveillance.