New Zealand and Australia are regarded as world leaders in the field of biosecurity, the management of invasive animals and plants including aquatic species. This paper presents an overview of the history and current governance of aquatic invasive species management in New Zealand. Its main focus is the input of biosecurity science, focussing primarily on the proactive management of invasive freshwater plants, and application in Australasia and other Pacific nations. Examples of proactive management actions include; identification of invasive species off-shore to prevent importation, management at the border, mitigation of introduction/dispersal pathways, surveillance for new incursions, incursion response and national eradication programs. Many of these actions are informed and supported by the development and application of risk assessment tools. The success of these initiatives within New Zealand is aided by geographical isolation and a relatively small population size, recognition of the need to protect an economy based on primary production from invasive species, strong effective legislation and biosecurity science directly linked to policy and management.

Global eel production through aquaculture has grown over 500% since the mid-twentieth century, with much of production occurring in East Asia. Recent proposal of Anguilla mossambica (Peters, 1852) (African longfin eel) aquaculture in the U.S. State of Michigan highlighted a need for greater unders tanding of potential risk posed by introducing this species to the United States and the Great Lakes region of North America. U.S. Fish and Wildlife Service rapid risk screening had previously characterized this species as posing “uncertain” risk to the contiguous United States. The aquaculture petition motivated a multi-expert risk assessment, an approach that promoted synthesis of published and unpublished knowledge on the poorly-studied A. mossambica along with tracking and quantification of uncertainty. A group of six scientists with expertise in eel biology, eel conservation, or fish health provided inputs to run the U.S. Fish and Wildlife Service’s Freshwater Fish Invasive Species Risk Assessment Model (FISRAM). As a Bayesian belief network, FISRAM required experts to estimate probabilities of harm to native species, ecosystems, and humans by a variety of mechanisms, as well as estimate probabilities of habitat suitability and transport. In their responses, experts emphasized lack of knowledge about many ecological interactions involving A. mossambica. However, they consistently rated its probability of transport high and expressed particular concern about concurrent introduction of the swimbladder nematode Anguillicoloides papernai (Moravec and Taraschewski, 1988) that parasitizes A. mossambica. Mean predicted probability that A. mossambica would be invasive, i.e., cause economic or environmental harm or harm to human health, was 0.24 when considering climate match to the Great Lakes basin only, and 0.57 when considering climate match to the contiguous United States. The range of predicted probabilities across experts was extreme. The State of Michigan has now used the results of this risk assessment to inform new pathogen testing and facility requirements in support of a recirculating aquaculture system (RAS) for A. mossambica in Michigan.

Non-native invasive crayfish continue to threaten ecosystems across the globe. However, factors that increase the risk of these introductions and subsequent establishment have yet to be fully elucidated. This study takes place in the US state of Michigan, where in 2013 several carcasses of red swamp crayfish (Procambarus clarkii) were discovered at popular fishing locations. Following this discovery, we explored possible modes of entry P. clarkii might use to invade Michigan by visiting various retailers that sold live crayfish and surveying classroom use of crayfish. We visited retail shops in 2014 and again in 2015 to determine if these stores continued selling live red swamp crayfish following a ban on possession of live red swamp crayfish enacted in late 2014. However, in 2017 we discovered established populations of P. clarkii in several ponds in southeast Michigan and a lake in the southwest portion of the state. These discoveries offered an opportunity to qualitatively compare our assessment of potential vectors with an ongoing invasion and to determine the effectiveness of the prohibition on live P. clarkii sales. Our assessment of potential vectors indicated that classrooms and live food markets are the most likely sources of the invasion, but none of the vectors we explored were risk free. In particular, we found that the number of retail shops selling live P. clarkii in 2014 actually increased following the prohibition, indicating the need to ensure the cooperation of industry and individuals in preventing the introduction and spread of non-native invasive crayfish. The results of this study can be used by natural resource managers to help identify vectors that move non-native invasive crayfish across political boundaries and illustrate the importance of restricting and prohibiting the movement of non-native invasive species across boundaries, or into new ecosystems.

Methods to reduce the introduction and spread of Invasive Alien Species (IAS) are key to reducing the economic, environmental and social impacts of IAS. IAS propagules can be moved around accidentally on clothing and equipment used in agriculture, transport, trade and recreation. Campaigns to slow the spread of aquatic IAS encourage water users to check, clean and dry their equipment and clothes, using hot water during the cleaning process where feasible. The UK Check Clean Dry biosecurity campaign recommends immersion in hot water (45 °C) for 15 minutes, however, implementation time may be a barrier to adoption of biosecurity practices. Here we aim to refine the advice given and test the efficacy of hot water treatment in actual conditions, with a view to reduce the recommended time to clean equipment while still preventing spread. The effectiveness was tested for a range of temperature (40, 45, 50, 55 and 60 °C) and time (10 seconds, 1, 5, 10, 15 minutes) treatments in killing IAS propagules of two invasive aquatic animal species (Dreissena polymorpha, Dikerogammarus villosus) and two invasive aquatic plant species (Myriophyllum aquaticum, Crassula helmsii), which are of global/national importance. For both invasive animal species, 100% mortality was achieved at all temperature and time treatments. However, plant mortality was affected by both temperature and time, with higher mortality resulting from higher temperatures and exposure times. Immersion for the recommended 15 mins at 45 °C caused complete mortality of C. helmsii, but only 40% mortality of M. aquaticum. Immersion in water at 50 °C or higher led to 100% mortality for C. helmsii and 90% mortality for M. aquatium at shorter treatment durations of 5 or 10 mins. In addition, immersion in water at 60 °C caused 100% mortality after only 1 minute exposure. To ensure adoption and application of biosecurity practices, guidance should be simple, consistent and safe. For practical application in field we recommend, where feasible, immersion of equipment in water at 50 °C for a minimum of 5 minutes to achieve high mortality of IAS propagules.

Zebra mussels (Dreissena polymorpha) have continued their spread within inland lakes and rivers in North America despite diligent containment and decontamination efforts by natural resource agencies and other stakeholders. Identification of newly infested waterways by early detection surveillance programs allows for rapid response zebra mussel eradication treatments in some situations. Previous eradication treatments have occurred over a broad range of water temperatures which have influenced the efficacy of molluscicides. Natural resource managers will benefit from knowledge regarding the impacts of water temperature and exposure duration on the toxicity of molluscicides to zebra mussels. In particular, temperature specific data are needed to inform the selection of an effective molluscicide and the proper dose that will induce 100% zebra mussel mortality. We evaluated the influences of temperature and exposure duration on the toxicity of two U.S. EPA-registered (EarthTec QZ and Zequanox) and two nonregistered (niclosamide and potassium chloride) molluscicides to zebra mussels at water temperatures of 7, 12, 17, and 22 °C. Our results indicate that treatment options for the eradication of zebra mussels in waters ≤ 12 °C include 336 h or longer treatments with EarthTec QZ and KCl as well as treatments with niclosamide ≥ 24 h in duration. In waters ≥ 17 °C, multiple toxicant and exposure duration combinations are potentially effective for zebra mussel eradication. On-site or in situ zebra mussel bioassays are a useful tool for the evaluation of treatment efficacy.

Control technology for dreissenid mussels (Dreissena polymorpha and D. bugensis) currently relies heavily on chemical molluscicides that can be both costly and ecologically harmful. There is a need for more environmentally neutral tools to manage dreissenid mussels, particularly in cooler water. Carbon dioxide (CO₂) has been shown to be lethal to several species of invasive bivalves, including zebra mussels and Asian clams (Corbicula fluminea). We evaluated the effectiveness of unpressurized infusion of CO₂ for 24 to 96 h (100 000–300 000 µatm PCO₂) at a water temperature of 12 °C on mortality, byssal thread formation, and attachment of zebra mussels. The safety of elevated CO₂ to a nontarget native freshwater mussel (Fatmucket, Lampsilis siliquoidea) was also determined. Elevated PCO₂ exposure induced narcotization and reduced attachment of zebra mussels within 24 h. Mortality increased with exposure duration and PCO₂. An estimated LT50 (lethal time to produce 50% mortality) for fixed PCO₂ ranged from 24 h at 275 000 µatm to ~ 96 h at 100 000 µatm. Exposure of zebra mussels to CO₂ for 96 h caused 80–100% mortality at all treatment levels. Fatmucket juveniles survived all PCO₂ treatments but burial and byssal thread production were adversely affected during exposure. Our results demonstrate that CO₂ is a viable option for management of zebra mussels in cool water and may have less adverse effect for native lampsiline mussels than current-use molluscicides.

Reservoirs along the lower Colorado River are infested with Dreissena rostriformis bugensis (Andrusov, 1897) (quagga mussel) and Cordylophora caspia (Pallas, 1771) (colonial hydroid). These invasive species, along with native freshwater sponges and bacteria, pose significant biofouling issues for hydropower facilities in the area. Biofouling in the generator cooler systems at Parker Dam, on Lake Havasu, AZ has resulted in increased annual maintenance costs of approximately $80,000/year. Medium pressure, hydro-optic ultraviolet (HOD UV) light systems with a 100 mJ/cm² target dose were installed on four main turbine cooling water lines and a raw water supply for the onsite water treatment facility at Parker Dam to mitigate biofouling. This study was designed to monitor the impact of HOD UV on biofouling over a two-year period. Comparison of biofouling dry weight from settlement plates exposed to HOD UV-treated and untreated water indicate a significant reduction in total biofouling after HOD UV exposure. Mussel settlement and bacterial sludge formation were consistently reduced in test chambers (bioboxes) despite lower than expected average HOD UV dose and contamination with untreated water. Hydroid larvae were not found in any plankton samples collected from the forebay at Parker Dam during the study, indicating asexual reproduction was the main source of downstream colony formation. Hydroid settlement reduction data after HOD UV treatment were inconclusive. The Parker Dam facility manager confirmed that biofouling-related maintenance of the coolers was reduced by 75 percent after the first year of HOD UV operation and eliminated in the second and third years after implementation.

Eradication and control measures for invasive aquatic organisms require innovative methods that maximise efficacy whilst minimising environmental damage. Such methods should also ideally utilise readily available materials and have a relatively straightforward field application. The Asian clam, Corbicula fluminea (Müller, 1774) is a high impact freshwater invader that can dominate macroinvertebrate communities and physically alter benthic habitats. Moreover, C. fluminea has shown a high degree of physiological and ecological plasticity, and has displayed a remarkable capacity for human-mediated passive dispersal. Globally, despite repeated efforts to mitigate spread and implement substantial population control measures, C. fluminea continues to invade and spread. Accordingly, effective population eradication and control measures are urgently required. Here, we examine the efficacy of commercially available dry ice (DI) pellets (i.e. solid CO₂ pellets at −78 °C) to kill C. fluminea, when applied both directly (water absent) and indirectly (clams submerged). Experiment 1 revealed the ability of 9 mm DI pellets to induce substantial C. fluminea mortality, with a direct application of 300 g DI at 5 min exposure inducing 100% clam mortality. In experiments 2 and 3, DI pellets of 9 mm induced higher clam mortality than 3 mm pellets, DI slices and mixed DI pellet sizes (3 and 9 mm) at simulated clam densities of 1179 and 3930 individuals m^-2, especially when clams were submerged. Experiments 4 and 5 showed that DI application was highly effective even with clams that were covered in gravel or mud, due to the freezing of their surrounding substrate. Accordingly, these results demonstrate that DI can potentially be used for effective, rapid response control and eradication of C. fluminea populations. Whilst promising, our laboratory results require scaling up to field application and examination of the effects of water current, substrate, increased water depth, and greater C. fluminea population densities.

Rapid reaction to the initial discovery of invasive alien species (IAS) is key to eradication, but this is often frustrated by lack of resources and coordinated actions. However, examples of successful eradications may encourage and empower others to follow. Chub (Squalius cephalus) were illegally introduced into the River Inny in Ireland in the late 1990s or early 2000s, reputedly by anglers. The habitat in this river is favourable for chub and, should this species establish, it would likely compete with the indigenous fish communities and impact on other flora and fauna. Central Fisheries Board (now Inland Fisheries Ireland) coordinated chub removal operations and provided the necessary resources (manpower and equipment) to effectively remove chub from this large river. Three electric fishing crews supported by two tank boats and land-based personnel were required in each operation to effectively remove the chub. These crews worked on this task each year between 2006 and 2013. Between 2006 and 2008, 24 adult and two juvenile chub were removed and euthanised. In 2008, two chub were radio-tagged, released back to the river and tracked monthly for 12 months. Over the next two years these “Judas” chub, and two untagged male chub that were located in proximity to the tagged fish, were removed from the river. Intensive electric fishing of the river and regular contact with the local angling community between 2010 and 2017 revealed no further chub specimens. Monitoring of the fish populations in the river will continue but it is suspected that chub may have been eradicated from this river system and, hence, from the island of Ireland. This provides a rare case study of the potential to eradicate aquatic IAS when rapid reaction is resourced and coordinated.

Invasive sea lamprey (Petromyzon marinus Linnaeus, 1758) are currently managed by the Great Lakes Fishery Commission in an effort to reduce pest populations below levels that cause ecological damage. One technique to improve stream population assessments could be molecular surveillance in the form of environmental DNA (eDNA) monitoring. We developed and validated four probe-based quantitative polymerase chain reaction (qPCR) assays, then used two probes (cytb, nd1) to determine whether eDNA concentration was correlated with adult and larval sea lamprey density in the lab. We found a strong positive correlation between adult sea lamprey densities of 2, 20, and 200 individuals/2000L and eDNA concentrations in tanks using both assays (cytb, nd1). For larval laboratory tank density trials, eDNA concentrations were generally near our limit of quantification and there was no significant difference in copy numbers detected between larval sea lamprey densities of 1, 5, and 25 individuals/28L. Therefore, we examined detection probability rather than concentration with laboratory tank densities. We observed a trend of increasing detection probabilities with increased larval sea lamprey density that approached significance suggesting that when DNA copy numbers are low, detection rates may be more informative in predicting varying densities of larval sea lamprey. The ability to assess sea lamprey densities from a water sample could be a powerful tool to improve traditional assessment and stream ranking techniques. Further refinement of this method in the field may make eDNA surveillance of sea lamprey a reliable part of stream assessments. Rapid eDNA analysis from many streams may help focus traditional assessment efforts, thereby improving the efficiency of invasive sea lamprey control efforts.

As international regulations governing the discharge of living organisms in ships’ ballast water enter into force, port state authorities will require a device for compliance inspectors or their designees to potentially use onboard ships to conduct compliance testing. Importantly, the device must be easy to transport, quick to connect to the main ballast water pipe, and reliable in collecting a representative sample of ballast water flowing through the pipe. To that end, a pocket-sized Compliance Sampling Device (CSD) was designed, fabricated, and validated. The CSD incorporates a fixed-orifice flow meter and a valve for controlling flow. Experiments were conducted to evaluate the accuracy and precision of flow measurements using the CSD. To determine whether the restricted flow through the device causes loss or damage to organisms, concentrations of living organisms and photochemical yield measurements of microalgae collected from the CSD were compared to controls (samples of water freely flowing through an unobstructed hose). No significant differences in concentrations of organisms or photochemical yield measurements were observed between samples. Results from these experiments showed that the device would be acceptable to collect compliance samples aboard ships.

With the entry of the Ballast Water Management Convention into force, ballast water discharged from ships must meet standards limiting the concentrations of living organisms. Monitoring devices to confirm compliance with these standards would ideally be portable, easy-to-use instruments capable of rapid and accurate shipboard analysis of ballast water. Following a framework established for the validation of such potential devices, six devices were evaluated in a series of laboratory and field tests at three contrasting coastal locations. Devices were designed to quantify organisms in the ≥ 10 and < 50 µm size class. In all cases, the compliance monitoring devices were compared to the agreed-upon performance standard for quantifying living organisms: microscopy-based, vital fluorophore approach. Specific results from these validations are available elsewhere, although examples are shown to demonstrate the analytical and statistical approaches used for gauging—with data analysis and statistical approaches—each device’s performance. Each metric used to evaluate devices (e.g., linearity, precision, and accuracy) was informative. However, linearity between the microscopy-based method and the compliance devices, especially along a large range of organism concentrations, would not be suitable for establishing performance criteria. Concentrations well below or above the limit for this size class (10 living organisms mL^-1) would be easily categorized as meeting or exceeding discharge standard and their values do not need to be well constrained and pinpointed. Precision, when measured as the coefficient of variation, was sensitive to the dimensions and scale of the devices’ measurements, as certain devices calculated and reported cell concentrations, whereas other devices reported non-dimensional v alues along a wide dynamic range. Accuracy, defined as the agreement between the compliance device and the standard approach as to whether the sample met or exceeded the discharge standard, was measured by logistic regression analysis. Following this analysis, the likelihoods of detecting exceedances based upon cell concentration were calculated for each field site and cultured test organism. Accuracy was useful in defining the likelihood of correctly identifying an exceedance, and these likelihoods could be calculated for a range of cell concentrations. The concurrent testing of multiple compliance devices minimized the analysis burden as well as the logistical hurdles associated with field testing at multiple—for this study, three—locations. Eventually, the test procedures could be modified to measure variation among different units of the same device or applied to actual measurements of ballast water rather than communities of ambient organisms or cultured microalgae.

Outreach is an important element of scientific communication and a prescribed element of many projects, but few scientists have training in communications. This paper describes the outreach element of a project on invasive alien species. A communications plan was drawn up to streamline communications efforts, allowing us to take advantage of unanticipated opportunities to engage with the public, while still maintaining the desired focus, using minimal resources. Here, we use two simple metrics—“passive reach” and “interactions”—to measure the extent and the intensity of communications, and we also look at the advantages and limitations provided by different media. Broadcast media and social media have the capacity to reach a wide audience, but have a low percentage of interaction. Workshops and citizen science events tend to reach a much smaller audience, but generate greater levels of engagement. Understanding these dynamics is important in designing an effective communications plan, which uses the minimum number of resources to generate maximum impact. Building the credibility of the researcher or the project means that your research will reach a wider audience, and your message is more likely to have an impact.