Aotearoa-New Zealand was uninhabited by humans until c.1280 AD and almost 90% of its freshwater fish species are found nowhere else on earth. Now is the ideal time for the European derived biocontamination index to be adopted for freshwater fauna in Aotearoa-New Zealand. The index was developed nearly two decades ago for freshwater macroinvertebrates has been successfully used in several studies throughout Europe and in the British Isles. There is no index like this, which accounts for both the relative abundance and species number of non-natives, currently being applied to Aotearoa-New Zealand’s freshwater systems, either for macroinvertebrates or fish. This is despite the presence of many introduced fish such as trout and catfish, which are known to impact on native species, many of which are rare, culturally “treasured” and under the threat of extinction. In addition, the very recent detection (May 2023) of the Gold/Asian clam, Corbicula fluminea, which is an “ecosystem engineer” that could arguably have the greatest ecological impact of any freshwater animal invader so far, makes the need for such an index even more compelling. Simple examples of publicly available fish species datasets are used to show how the biocontamination index could easily be applied with minimal extra effort to Aotearoa-New Zealand’s systems and be used as an additional fisheries management tool. While some non-native fish are valued, some are designated pests and, in both cases, the biocontamination index could aid a variety of different management strategies. It is also suggested how the index could be employed, in respect of the surveillance and suppression strategy currently being adopted by the government in response to the recent Gold / Asian clam invasion.

Identifying areas susceptible to invasion by an alien species is a strategy of prevention. We used national herbaria and global databases to assess the invasion trends of the two aquatic invasive species Ludwigia hexapetala and Ludwigia peploides subsp. montevidensis in Italy. We defined the invasion status with invasion curves and predicted potentially suitable areas with Species Distribution Models based on WorldClim variables and the human footprint index. Low seasonal variation in temperature and precipitation, temperature ≥ 20 °C in the driest period of the year and low precipitation in the coldest period are the bioclimatic factors that most account for the potential distribution of the two species. The human footprint has a lower relative importance than bioclimatic variables. All Italian peninsula appears as a suitable bioclimatic environment for the invasion of the two Ludwigia species, with over 90% of areas with high suitability lying below 600 m altitude. Only mountain regions and the islands appear less suitable. The agricultural land at the foothill of the Appennine in the Mediterranean region is the most vulnerable to the invasion. Considering the trend of the invasion curves, which have been sharply rising for the latest decades, there are reasons to expect that the alien Ludwigia species will continue their expansion, if no timely and effective actions are taken. Informative campaigns, accurate monitoring and prompt management are fundamental preventive tools in areas predicted as vulnerable to invasion by this study.

Commercial shipping activity plays a crucial role in the unintentional primary and secondary introduction of aquatic Non-Indigenous species (NIS), with ballast water (BW) and hull biofouling being the two major vectors of NIS transportation. The aim of this study is to identify potential high-risk donor port areas that may act as pools for NIS introduction in Saronikos Gulf, Greece. For the purpose of the study, we conducted a regional risk assessment and produced a NIS watch list based on the commercial vessel arrivals at the major ports of the Saronikos Gulf (Piraeus and Elefsis) for the period 2020–2022. In our risk analysis, we used the two most important factors for ship-mediated species introductions identified in the literature: salinity and biogeographic region of the voyage last origin ports. Then, combined with data on vessel arrivals, based on marine traffic data collected from the Marine Traffic online platform, we produced a NIS watch list for the study area. The most high-risk ports for primary introductions were found to be in the Temperate Northern Atlantic (e.g. Gemlik, Ambarli, Asyaport and Derince in Türkiye, Sines in Portugal), Western Indo-Pacific (e.g. Jeddah in Saudi Arabia, Aqaba in Jordan) and the Central Indo-Pacific (e.g. Singapore). For secondary introduction, the most high-risk voyage origin ports are located in the Levantine Sea (e.g. Limassol in Cyprus, Alexandria and Port Said in Egypt, Haifa and Ashdod in Israel, Iskenderun, Mersin and Nemrut in Türkiye), the Aegean Sea (e.g. Izmir in Türkiye) and the Ionian Sea (e.g. Marsaxlokk in Malta). Our watch list included 44 high risk and 13 medium risk NIS to be transferred to Saronikos Gulf. Of these, 38 high-risk species are already present in the Mediterranean, 6 high-risk species are absent from the Mediterranean and 18 species pose a high risk for both primary and secondary introduction.

Efforts to prevent the spread of aquatic invasive species (AIS) have been widely implemented to mitigate economic and environmental harms. Boater education, watercraft inspection, and hot water decontamination are popular strategies for preventing AIS spread through recreational boating. However, few studies have quantified the effectiveness of these strategies under field conditions. We estimated the effectiveness of AIS preventions based on the performances of boaters, watercraft inspectors, and hot water decontaminators. Participants (n = 144) were recruited at public water access sites in Minnesota (n = 56) and Wisconsin (n = 1). Each participant was asked to inspect and remove AIS from a boat consistently staged with macrophytes in the same six locations, adult zebra mussels in two locations, spiny water flea in one location, and residual water in one location. The types and amounts of AIS removed were used to estimate the effectiveness of each prevention method. We observed that removal rates varied by type of AIS and location – the locations with macrophytes were most commonly removed by all participant types. There were also regional (within or outside of the Minneapolis/Saint Paul metro area) differences for some species, such as spiny water flea, perhaps due to regionally specific outreach campaigns. Hot water decontamination had the highest percentage of intervention effectiveness (mean = 84.4%), but was not significantly better than watercraft inspection (mean = 79.2%). Our results suggest boaters are less effective (mean = 56.4%) at removing AIS than both trained professional groups in this study, but nevertheless play an important role in AIS prevention. Furthermore, we identified areas of the boat that were often overlooked (e.g., winch, bow line, transducer) by boaters and could be incorporated into future outreach campaigns. We observed high variability in the actions (i.e., time spent, places looked, methods used) taken among individuals from each participant group, revealing opportunities for standardizing outreach and professional training to maximize effectiveness. This was particularly evident among decontaminators, who often made risk-based decisions to modify the protocol and relied on equipment that often failed to reach minimum temperature thresholds for lethal exposure. This study can better inform AIS managers as they weigh the cost-benefit of each prevention strategy to meet their management objectives.

The quagga mussel, Dreissena bugensis, is an invasive freshwater bivalve that causes significant economic and ecological damage. Numerous techniques are currently being investigated to help control their spread. X-ray irradiation has been used in different techniques to help control the spread of invasive species, either through decontamination or by the production of sterile male that reduce reproductive populations (Sterile Male Release Technique). Most studies have focused on terrestrial species, fewer looking at the effects of irradiation on aquatic species. This study was designed to evaluate the effects of x-ray irradiation on quagga mussels both in its effectiveness to kill mussels or to produce sterile males. Adult mussels were irradiated with a range of exposures from 0 (control), 6, 30, to 50 Gy to determine the effect on quagga mussel survival and impact on reproduction. The results demonstrated that x-ray treated quagga mussels had lower developmental success than the control. Adult quagga mussels were highly tolerant of x-ray irradiation with high survival rates (> 95%) after treatment. Mussels from all treatments produced motile sperm and these sperm were able to bind and fuse with eggs. There was a decrease in sperm binding between treatments, but fertilization still occurred. Fertilized eggs in all treatments were able to divide and produce swimming trochophores, but irradiation appears to decrease development between zygote and trochophore stage. The current experiment was not able to produce completely sterile males, even at the highest irradiation of 50 Gy in a single 8-minute session. The current experiment did not find an x-ray dose leading to the generation of 100% sterile males. Even at higher doses, x-ray irradiation may not be realistic for implementation.

As environmental DNA (eDNA) becomes a fixture in the invasive species management toolbox, expectations of its utility extend beyond presence/absence to analyses that provide more detailed information about target populations. Studies with fish and other vertebrates have reported moderately reliable, positive relationships between eDNA concentrations and biomass. However, few studies have considered this relationship in invertebrates. To address this gap, we investigated whether increasing biomass of apple snails (Pomacea maculata) resulted in a similar predictive relationship with eDNA concentration, and we did so under cold conditions that make apple snails less conspicuous and more difficult to detect with traditional methods. Placing snails in either distilled or stream water, we used a species-specific quantitative PCR assay to measure eDNA concentrations after 24 hr over an apple snail biomass gradient (0, 2, 4, or 6 snails; 143 to 624 g total biomass). Detection success of eDNA derived from apple snails kept in a small volume (i.e., 13 L) of cold water (13 °C) averaged 66% overall. Successful detection in distilled water (75%) exceeded the overall average. Lower detection efficiency occurred in stream water (58%). Despite the cold conditions, we observed snail activity in 90% of our replicates, but net eDNA accumulation failed to reflect patterns commonly observed with vertebrates. Censored regression modeling efforts, which account for a disproportionate number of zeros (i.e., non-detections), identified a significant predictive relationship between snail biomass and eDNA concentration, but only starting at a high amount of biomass (~ 422 g). Future management strategies to monitor apple snails will likely include eDNA, but its utility in ascertaining biomass remains unclear. Considering the ecology of eDNA of invasive invertebrates will help bolster managers’ ability to understand the utility and limitations of this valuable tool.

We report biosecurity interceptions of Oryctes rhinoceros in Australia, New Zealand, Guam, United States, and other jurisdictions to provide the first such published assessment for this highly invasive species. Between 2003 and July 2023 New Zealand found O. rhinoceros 13 times. Between 2002 and July 2023 Australia found Oryctes rhinoceros 14 times. Since 2017 inspections in Guam detected individuals twice. Between 2003 and 2014, beetles were found eight times at ports in the United States. No credible interceptions were made in the European Union. Four other intercepts were reported from two other jurisdictions. There were very little commonalities among the intercept data. All but one detection were of adults, and of the 14 adults that were sexed, eight were female and six were male. From the Australian data, which included month of detection, there was no seasonality associated with detections. Detections were associated with a broad array of commodities or situations. Oryctes rhinoceros appears to be a generalist passenger, being accidentally transported by a wide variety of means at any time. This finding indicates that there is little possibility of focusing on any specific commodity, packaging, vessel, or season to detect accidental transport of this species. Instead, biosecurity vigilance is required on all goods and vessels arriving at, or leaving, destinations.

The distribution of the ecologically damaging invasive Cuban Treefrog (CTF, Anura, Hylidae, Osteopilus septentrionalis) in the USA is documented primarily by users of invasive species applications (apps) such as the Early Detection and Distribution Mapping System (EDDMapS). The purpose of this case study was to investigate spatial and temporal patterns in EDDMapS’s CTF records from Florida, USA. With the accessibility of geolocated records and machine learning algorithms, predicted species distribution models (SDMs) need to be revisited to explore their accuracy as new records become available. Utilizing the machine learning TreeNet® Classification algorithm, I constructed an SDM from records uploaded in 1999–2020, mean monthly temperature and rainfall patterns from 1999–2020, 2020 United States census data, and proximity to water and residential land cover types. Of the 1,042 geolocated records, the mean annual number of entries was more than 30 times greater from 2010–2020 than years prior, indicating greater utilization of the app with time. Residential areas and wetland land cover categories represented 35.2%, and 29.8%, respectively, of the locations where the CTF had been recorded. The variables mean monthly temperature and minimum temperature during the coldest quarter contributed the greatest contribution to the model with predicted suitable areas primarily in southern Florida. Using 2021–2023 records to validate the SDM, 96.7% of the 398 geolocated records were associated with a relative occurrence index ≥ 0.80, indicating the model’s predicted suitable areas performed well. Regional programs that aim to train, mentor, and incentivize the public to report geolocated presence and absence observations with microhabitat descriptions would improve the accuracy of predicted suitable areas for invasive species whose records derive mainly from invasive species monitoring apps.

Effective cross-border management of invasive alien species is dependent on robust data sharing among responsible authorities. This need is particularly pronounced for species like aquatic rodents, such as muskrat and coypu, which rely on interconnected hydrographic networks for dispersal. The LIFE MICA project sought to enhance cross-border cooperation between the Netherlands, Germany (Lower Saxony), and Belgium (Flanders) by centralising data on the occurrence and management of invasive alien rodents. Project partners from seven institutions collaborated to develop innovative detection and management methods, such as smart camera trapping, eDNA analysis, and smart life traps for muskrat and coypu. Prior to the LIFE MICA project, management and occurrence data for muskrats and coypus in a substantial part of northwest Europe were fragmented in isolated data repositories. To address this issue, the project adopted an open data approach based on the Global Biodiversity Information Facility (GBIF), resulting in the publication of nearly one million new muskrat and coypu observations dating from 1987 to the present day. This initiative represents a significant step towards improved collaboration and data sharing in the management of invasive alien rodents across a wide geographic area in northwestern mainland Europe.