The 23^rd International Conference on Aquatic Invasive Species (ICAIS 2024) highlighted ongoing advancements and continuing challenges related to aquatic invasive species (AIS). Keynote speakers touched on developments in genomics, artificial intelligence, and regulation that are improving AIS management, while also highlighting the continuing risks of environmental disturbance or social inequity in hindering progress. A few authors in this special issue touch on the benefits of inclusive language to increase support and collaboration, the critical role of communicating with and educating stakeholder groups (including online communities), and the benefit of gathering data alongside outreach. Two papers touch on the improvements in ballast water management as the International Maritime Organization (IMO) ballast water performance standards come into force, while also highlighting ongoing challenges. Improved tools can also help predict or manage AIS. Improvements in biopesticides and horizon scanning are described in this special issue. Finally, understanding the potential impacts of AIS is a critical part of management decision-making, and three papers examine those impacts. Although AIS will continue to cause harm globally, the advances highlighted in this special issue will help managers, scientists, and stakeholders to manage the risks more effectively.

Ships’ ballast water has been a global pathway for the introduction and spread of harmful aquatic organisms and pathogens. Following the first stages of the implementation of the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (the Convention) to mitigate such introductions, a number of challenges were identified. Broadly, meeting the requirements of Regulation D-2 (the standard that limits the concentration of viable organisms in ballast water discharges) and balancing the operational demands of ballast water management with cargo activities have been difficult. A workshop was held in Halifax, Nova Scotia, Canada, in May 2024 at the 23^rd International Conference on Aquatic Invasive Species (23^rd ICAIS) to bring together global experts with relevant scientific, regulatory, and operational knowledge with the aims to, first, take stock of current challenges and second, identify solutions to improve future implementation of global ballast water management. Specific challenges were identified as: unexpectedly low rates of compliance (about 50%) with the discharge standard for organisms ≥ 50 µm in minimum dimension (the largest size class in Regulation D-2, typically zooplankton), inoperability of some equipment in water with high turbidity, and difficulty maintaining equipment. Areas for improvement include: strengthening equipment testing to improve compliance rates, comprehensive training for seafarers, streamlining administrative processes to support equipment modifications, developing standard procedures for equipment operation and maintenance, introducing enforcement activities based on document checks, and, implementing periodic and randomized testing to identify reasons for BWMS failure with a focus on organisms ≥ 50 µm. Workshop participants discussed how lessons learned from the implementation of the Convention to curtail ballast water-mitigated invasions could be applied in the ongoing development and future application of international biofouling regulations and guidance—another major global introduction pathway—with collection of data on the efficacy of in-water cleaning of ships using standardized, verified methods viewed as the most immediate and important step toward management development.

Ballast water discharge has long been recognized as an important vector for introducing aquatic invasive species, prompting the implementation of ballast water management regulations globally to mitigate this risk. Recently, ballast water management regulations have transitioned to performance-based standards, with most vessels installing and operating onboard ballast water treatment systems. To evaluate the adoption and utilization of ballast water treatment systems during this transition period, this study analyzed ballast water reporting form data from vessels arriving in Canada from foreign ports in 2020. Between January and December, the percentage of vessels discharging ballast water with treatment systems installed increased from 38% to 62%, and the percentage of discharge volume managed using treatment systems doubled, increasing from 22% to 45%. However, not all vessels with treatment systems were using them, with monthly usage rates ranging from 63% to 78%. When treatment systems were not in use, ballast water was often managed through ballast water exchange, while some ballast was sourced from the mid-ocean or discharged unmanaged due to regulatory exemptions related to the ballast water exchange exemption zones. Possible factors preventing consistent use of ballast water treatment systems include equipment breakdown, maintenance issues, crew inexperience, or challenging port water conditions hindering system performance. These factors underscore the need for robust contingency measures until advancements in treatment system technology or reliability provide lasting solutions.

Biopesticides are comprised of microorganisms, their natural metabolites and other natural biochemicals such as some plant extracts and pheromones. There are proven examples of biopesticides being used for aquatic invasive species (e.g., Bacillus thuringiensis israelensis and Bacillus sphaericus for mosquito larvae control) and other pests. Based on their safety and low risk to the environment, there should be more examples of biopesticides for control of aquatic invasives. While biopesticides have been around for over seventy years, starting with Bacillus thuringiensis, they are experiencing rapid growth with compounded annual growth rates of 10–20% versus 2–3% for synthetic chemical pesticides. Biopesticides offer the potential of effective control, biodegradability, low risk to non-target organisms and reduction of carbon footprint/greenhouse gas emissions compared to synthetic chemical pesticides. Challenges to the adoption of biopesticides in agriculture include a lack of awareness and education in testing and deploying their unique modes of action and lingering perceptions of high cost and low efficacy. New tools of genomics, artificial intelligence, machine learning, and precision fermentation allow scientists to discover and develop new effective microbial biopesticides more rapidly and more efficiently. Considering availability of these new tools and on the other hand, a relatively untapped fraction of nature’s microorganisms thus far, along with their metabolites, for use as biopesticides in agriculture, there is high potential for discovery and development of new, more potent and cost-effective microbial natural products for use against aquatic invasive species.

The aquarium trade transports countless ornamental species around the globe, creating greater opportunities for unwanted nonnative organisms to be released into the wild. The buy-sell-trade classified sections of print newspapers are a relic of the past. Instead, hobbyists now use social media platforms and Internet forums to create virtual communities where the acquisition of plants and animals via informal peer-to-peer transactions is possible. The present study aimed to investigate the behavior of aquarium hobbyists by administering a survey to Facebook groups in the U.S. that facilitate, among other things, the rehoming of aquatic organisms. In practice, “rehoming” actually refers to the selling, trading, or gifting of plants and animals, despite such activities being prohibited by Facebook’s commerce policies. According to 1,743 hobbyists, over half (54% of responses) of the respondents sometimes to very often engaged in peer-to-peer transactions (i.e., selling, trading, or gifting) using online platforms, with the most common motivator for owning unwanted organisms resulting from accidental or purposeful breeding (25.5%). Respondents reported local delivery or pickup of unwanted organisms in a different county (36.2% and 41.0%, respectively), state (13.9% and 29.1%), or country (6.2% and 5.6%). A total of 1.3% of hobbyists reported releasing live organisms into the wild, and over one-third (37.2%) claimed to have known someone who had done the same. Respondents who self-identified as releasing live organisms in the past (“releasers”, 2.9% of respondents) reported similar levels of invasive species knowledge, yet were over three times (15.7% of “releasers” vs. 5.3% of “non-releasers”) more likely to be unconcerned about their negative impacts, and over twice more likely to report feeling not responsible for helping prevent their spread compared to non-releasers (19.6% of “releasers” vs. 9.6% of “non-releasers”). Social media platforms, such as Facebook, offer extensive opportunities for peer-to-peer transactions involving live organisms. Outreach campaigns specifically targeting online hobbyists are necessary to discourage the intentional release of organisms into the wild, in addition to effective autonomous surveillance of discussion forums and enforcement of existing Facebook policies that prohibit the buying, selling, and trading of live animals.

Aquatic ecosystems are among the most impacted by biological invasions and eradicating invasive species from these systems proves to be very challenging. Thus, it is crucial to prevent new introductions, and the secondary spread of invasive alien species (IAS) already present through a collective effort of all water users. Adopting biosecurity measures is an efficient way to decrease the unintentional transportation of IAS on equipment due to human activities. To inform the development of the first biosecurity campaign for Belgian anglers, a national online survey was conducted during the spring of 2023, generating over 3000 individual responses. This study had two main objectives: 1) to gain a better understanding of the risk of IAS transport by recreational anglers, and 2) to inform the development of a communication campaign by assessing anglers’ awareness and perception of the issue of biological invasions. The results revealed a major risk of anglers inadvertently introducing IAS into previously uninvaded ecosystems, either through the unintentional transfer of organisms during a single outing (25% of anglers) or by transporting them from abroad (45% of anglers). This risk is compounded by the fact that only 8% of anglers adhere to the full check-clean-dry routine after each trip, and mobile anglers were not necessarily more proficient at cleaning their equipment. Additionally, some anglers admitted to occasionally releasing bait or translocating undesired species. Despite limited awareness of biological invasions, respondents generally had a negative perception of IAS. As a result, anglers could be considered an ally in the fight against IAS. The results of this baseline survey will inform future action plans to reduce invasion levels and raise awareness among the angling community in Belgium. It will aid in designing adequate messages, efficiently reaching the target audience, and assessing the campaign's influence on angler habits and awareness.

There is a growing in-flux of non-indigenous species (NIS) brought to new locations via anthropogenic pathways, some of which are harmful to ecosystems, economies, and social and cultural health of receiving environments. In order to protect native ecosystems from invasion by novel NIS, watchlists of potentially problematic species are required but this task can feel overwhelming when considering the vastness of global biodiversity. To date in Canada, the Great Lakes are the only jurisdiction to have generated a freshwater NIS watchlist and published the associated methods. Here we compiled a working list of 4,446 species (plants, invertebrates, vertebrates) which was refined to 221 species based on taxa of interest (i.e. freshwater species), climate matching, invasion status and history, and associated vector presence, to focus on species relevant to the Maritime Provinces of Canada (i.e. Nova Scotia, New Brunswick, and Prince Edward Island). Using a rapid-level risk assessment tool applied to the refined species list, we identified 130 NIS as high-risk invaders to the Maritimes. We also identified numerous species with knowledge gaps that require further research. Common gaps included species’ ecological thresholds, summaries of direct and indirect ecosystem impacts, and socio-economic impacts of species. We also noted the vectors associated with each of the 221 species. Although this work is specific to the Maritimes, the methodology and species list (including risk assessments) could easily be adapted to other regions of Canada or elsewhere. This project represents the first Canadian-led multi-province, multi-taxon, large scale horizon scan aimed at identifying species for management action, including listing in legislation.

Minimizing overland transport of aquatic invasive species (AIS) via recreational watercraft is an essential component of invasive species spread prevention. Watercraft inspections at launch sites are a widely applied strategy to reduce human-mediated transport of AIS to protect priority waterbodies and offer public education and training of preventative cleaning procedures. Watercraft inspections also represent an opportunity to collect useful information for ecosystem managers on watercraft movement patterns and species occurrences that can be applied to risk assessments and early detection rapid response programs. New York State (NYS) in the Northeastern USA implemented use of a Watercraft Inspection Steward Program Application (WISPA) in 2018, which is a form-based survey that populates a centralized database with several data fields that include spatially explicit location, watercraft type, origin waterbody, and species observations. Coordinated and standardized collection of this data equips AIS managers with substantial information to make data-driven decisions. Here, we summarize the information collected in the WISPA database during the first six years of use and highlight two key management uses for this information using a set of eight popular destination lakes. Boater connectivity maps of origin-destination links are valuable to acknowledge the breadth of origins travelling to NYS destinations, and to identify the highest-magnitude connections that likely represent increased-risk pathways for species transport. “Hits” analysis is an applied mechanism to relate species interceptions to a confirmed presence database to identify previously undocumented species occurrences and direct early detection rapid response survey priorities. WISPA has been effective to establish the data infrastructure needed to support systematized data collection during watercraft inspection surveys and increase managers’ ability to make informed decisions about AIS management.

Horizon scanning, the systematic identification and risk assessment of potential non-indigenous species (NIS) for a given area of interest, is an important tool for preventative management of invasive NIS. However, existing horizon scans for invasive NIS exhibit methodological trade-offs, either being comprehensive in scope but resource-intensive (e.g. requiring large groups of experts) or resource-efficient but narrow in scope (e.g. focused on one taxon), neither of which are ideal for small-scale management contexts where managers are responsible for a broad scope of invasive NIS taxa but resources are limited. We developed a horizon scanning approach combining methodological efficiency with a broad scope and applied it to marine NIS in the Fisheries and Oceans Canada Maritimes Region (DFO Mar), a large geographic region in eastern Canada with a small management team that is a hotspot for marine NIS. We achieved a novel balance between comprehensiveness and efficiency by combining elements of existing horizon scanning methodologies with data-driven species filtering and an empirically optimized screening-level risk assessment (SLRA) protocol. We identified western Europe and eastern North America as the most likely source regions of marine NIS for DFO Mar, and compiled an initial list of 2525 potential NIS from these areas. After filtering this list for species of interest, using data from taxonomic and species distribution databases and the literature, we assessed 190 species using the SLRA protocol and flagged an additional 239 for future reassessment. Of the assessed species, 29 were determined to have a high relative risk of becoming invasive in DFO Mar, with 69 posing a moderate relative risk. The results of this horizon scan will inform marine invasive species management in DFO Mar. Additionally, the methodologies developed in this study can be adapted for use in horizon scanning exercises in other regions, particularly in small-scale management contexts.

Pycnogonids, or sea spiders, are ubiquitous arthropods present in most marine ecosystems. However, because of their usually low population densities, they remain understudied by zoologists despite presenting numerous unique biological features. The species Ammothea hilgendorfi (Böhm, 1879), native to the Northern Pacific Ocean, was introduced in Europe in the late 1970s and its presence has now been reported in several seas. Recordings of the species in Europe are sporadic and mostly do not exceed a handful of specimens. Hence, the populations have only been considered as introduced in the invasion process. The goal of this study is to investigate the first population of A. hilgendorfi at the Belgian coast (North Sea) during a 24-month monitoring through different proxies (phenology, biometry, developmental cycle). For the first time, our results demonstrate that this population of pycnogonids can be considered as established as it is able to complete its entire life cycle, including all larval instars, which are ectoparasites of hydroids. Moreover, it has developed in very high densities of individuals and has outnumbered by far the native sea spiders, which have almost disappeared, so it can also be considered as invasive sensu stricto. Their average density increased from the first year to the second, which indicates that the invasion has likely not reached its capacity yet. Since research on sea spiders has been very limited, this work emphasizes the importance of studying these animals, especially when the lack of knowledge undermines the assessment of their impact and their invasiveness potential.

Swimmer’s itch is a disease that can cause severe rashes on human skin, and is common in many recreational lakes in North America. The parasite responsible for this disease is an aquatic digenean trematode larva (cercaria) of the genus Trichobilharzia which has a complex life cycle. It needs two hosts to complete its cycle: a waterfowl as a definitive host and a snail (normally from Lymnaeidae, Physidae or Planorbidae families) as an intermediate host. So far, no study has mentioned the exotic banded mystery snail, Viviparus georgianus (syn: Callinina georgiana), as a host of this parasite. The aim of this project was to determine whether V. georgianus can be an intermediate host of the parasite responsible for swimmer’s itch. To verify this, we compared the infection prevalence rates of native and exotic snails in Lake Memphremagog (Quebec, Canada). After a 17 hour-exposure to artificial light at room temperature, snails were tested for cercarial infection. None of the V. georgianus released cercariae. Based on these results, we have not found any evidence to suggest that V. georgianus is an intermediate host of the parasite species. However, two indigenous snails Ladislavella sp. (Family: Lymnaeidae) and Helisoma anceps (Family: Planorbidae) were confirmed to release cercariae. The prevalence of the infection in native snails was 5% and the estimated average cercariae was between 60 to 1900 per 100 ml. Here, we present evidence that the exotic banded mystery snail does not contribute to the life cycle of the swimmer’s itch parasite in Quebec.

Asian mystery snails (Cipangopaludina chinensis Gray, 1834 and Cipangopaludina japonica von Martens, 1861) were introduced to the United States in the 1890s and have since spread to waterbodies across the country. Besides the classic effects of invasive species, mystery snails may accumulate and distribute metals in invaded ecosystems. Few studies have evaluated this phenomenon in non-native mystery snail populations, specifically regarding partitioning of metals between different tissues and shells, and metal maternal transfer. Our goal was to compare metal concentrations (Cd, Cu, Ni, Pb, Zn) of shells, tissues, and environment of mystery snails, and the extent to which metals are maternally transferred. Mystery snails, water, and sediment were collected from several locations in northwestern Pennsylvania, USA, between 2021–2023. Metal concentrations in environmental matrices, tissues, and shells of mystery snails were evaluated via inductively coupled plasma mass spectrometry. Snail metal concentrations were compared to environmental concentrations to determine allocation between tissues and putative routes of accumulation. All five metals were detected in mystery snail tissues, with evidence of substantial accumulation of Cd, Pb, and Ni. Bioconcentration and biota sediment accumulation factors revealed that for most metals, accumulation may have occurred from water, likely reflecting snail feeding strategies and metal bioavailability. Significant correlations between maternal and offspring metal concentrations were found for all five metals, but Cu showed elevated concentrations in offspring compared to mothers. This suggests maternal transfer, increasing potential trophic transfer through predation on juvenile snails. Quantifying metal concentrations in mystery snails provides insight into potential exposure risks and trophic transfer, with implications for evaluating adverse effects in native species.

Message frames and metaphors are commonly used within science communication to discuss complex topics, including invasive species. While these communication tools are undoubtedly helpful, the ecological process of invasion juxtaposed with the use of militaristic and nativist language can have unintended consequences that are counterproductive to management efforts. Species naming conventions are likewise complex, with some species bearing names that may reinforce xenophobic concepts or contain racial slurs. Despite the known need, there have been limited national efforts to develop better and more inclusive guidelines for invasive species communication. During National Invasive Awareness Week (NISAW) 2024, Sea Grant and the North American Invasive Species Management Association (NAISMA) hosted the Invasive Species Language Workshop which brought together researchers and practitioners from across environmental disciplines to address these communication needs and develop future objectives. The hybrid portion of the workshop, attended by more than 400 people, featured presentations on renaming species, standardizing terminology, message framing, social context and inclusivity, and interventions and collaborations. The in-person portion, attended by 15 people, used semi-structured discussions to share information, identify consistent issues, and to develop the following priorities: 1) Building Evidence of Impact and Harm; 2) Identifying Networks of Change and Building Support; 3) Co-Production of Interventions; 4) Operationalizing Interventions for Change. Further research can help illustrate the positive impacts of this work, while developing the pathways and programs to implement change. By embracing improved language and naming conventions, researchers and communicators can foster broader support and ultimately enhance invasive species management practices.