Marine Non-indigenous Species Research Articles

Using biophysical modelling and marine connectivity to assess the risk of natural dispersal of non-indigenous species to comply with the Ballast Water Management Convention

AbstractThe introduction of Marine Non-Indigenous Species (NIS) poses a significant threat to global marine biodiversity and ecosystems. To mitigate this risk, the Ballast Water Management Convention (BWMC) was adopted by the UN International Maritime Organisation (IMO), setting strict criteria for discharges of ballast water. However, the BWMC permits exemptions for shipping routes operating within a geographical area, known as a Same-Risk-Area (SRA). An SRA can be established in areas where a risk assessment (RA) can conclude that the spread of NIS via ballast water is low relative to the predicted natural dispersal. Despite the BWMC's requirement for RAs to be based on modelling of the natural dispersal of NIS, no standard procedures have been established. This paper presents a methodology utilizing biophysical modelling and marine connectivity analyses to conduct SRA RA and delineation. Focusing on the Kattegat and Øresund connecting the North Sea and Baltic Sea, we examine two SRA candidates spanning Danish and Swedish waters. We provide an example on how to conduct an RA including an RA summary, and addressing findings, challenges, and prospects. Our study aims to advance the development and adoption of consistent, transparent, and scientifically robust SRA assessments for effective ballast water management.

Non-indigenous species and their realized niche in tidepools along the South-East Pacific coast

Non-indigenous species (NIS) have the potential to colonize and become established in a wide range of coastal habitats. Species with broad environmental tolerances can quickly adapt to local conditions and expand their niches along environmental gradients, and even colonize habitats with extreme abiotic conditions. Here we report and document the distribution of eight marine NIS (four seaweed and four invertebrate species) found in tidepools along a 3,000 km latitudinal gradient along the Pacific coast of Chile (18.4°S to 41.9°S). The seaweed NIS Codium fragile, Capreolia implexa, Schottera nicaeensis and Mastocarpus latissimus were mostly distributed towards high latitudes (i.e., more southerly locations), where temperatures in tidepools were low. The invertebrate NIS Anemonia alicemartinae, Ciona robusta, Bugula neritina and Bugulina flabellata were more common towards low latitudes, where high temperatures were registered in the tidepools. Across the intertidal gradient, seaweed NIS were mostly found in pools in the mid and low intertidal zone, while invertebrate NIS occurred mostly in pools from the mid and upper intertidal zones. The realized niche spaces of NIS (based on the Outlying Mean Index, OMI) in the study area were mainly influenced by environmental conditions of temperature and salinity (along the latitudinal and intertidal gradients), while other tidepool characteristics (depth, surface area, exposition, and complexity) only had minor effects. Five of the eight NIS exhibited a realized niche space coinciding with the average tidepool environmental conditions, while marginal niches were occupied by species with affinities for specific temperatures and salinities along the latitudinal and intertidal gradients. Our results indicate that physiological tolerances to environmental factors play a fundamental role in the distribution of seaweed and invertebrate NIS in tidepools along the Chilean coast. This study confirms that tidepools offer suitable conditions for some seaweed and invertebrate NIS, potentially facilitating their invasion into new natural habitats.

Quantifying the probability of a successful marine bioinvasion due to source-destination risk factors.

The increasing spread of marine non-indigenous species (NIS) due to the growth in global shipping traffic is causing widespread concern for the ecological and economic impacts of marine bioinvasions. Risk management authorities need tools to identify pathways and source regions of priority concern to better target efforts for preventing NIS introduction. The probability of a successful NIS introduction is affected by the likelihood that a marine species entrained in a transport vector will survive the voyage between origin and destination locations and establish an independently reproducing population at the destination. Three important risk factors are voyage duration, range of environmental conditions encountered during transit and environmental similarity between origin and destination. In this study, we aimed for a globally comprehensive approach to assembling quantifications of source-destination risk factors from every potential origin to every potential destination. To derive estimates of voyage-related marine biosecurity risk, we used computer-simulated vessel paths between pairs of ecoprovinces in the Marine Ecoregions Of the World biogeographic classification system. We used the physical length of each path to calculate voyage duration risk and the cross-latitudinal extent of the path to calculate voyage path risk. Environmental similarity risk was based on comparing annual average sea surface temperature and salinity within each ecoprovince to those of other ecoprovinces. We derived three separate sets of risk quantifications, one each for voyage duration, voyage path and environmental similarity. Our quantifications can be applied to studies that require source-destination risk estimates. They can be used separately or combined, depending on the importance of the types of source-destination risks that might be relevant to particular scientific or risk management questions or applications.

Drop it all: extraction-free detection of targeted marine species through optimized direct droplet digital PCR.

Molecular biomonitoring programs increasingly use environmental DNA (eDNA) for detecting targeted species such as marine non-indigenous species (NIS) or endangered species. However, the current molecular detection workflow is cumbersome and time-demanding, and thereby can hinder management efforts and restrict the "opportunity window" for rapid management responses. Here, we describe a direct droplet digital PCR (direct-ddPCR) approach to detect species-specific free-floating extra-cellular eDNA (free-eDNA) signals, i.e., detection of species-specific eDNA without the need for filtration or DNA extraction, with seawater samples. This first proof-of-concept aquarium study was conducted with three distinct marine species: the Mediterranean fanworm Sabella spallanzanii, the ascidian clubbed tunicate Styela clava, and the brown bryozoan Bugula neritina to evaluate the detectability of free-eDNA in seawater. The detectability of targeted free-eDNA was assessed by directly analysing aquarium marine water samples using an optimized species-specific ddPCR assay. The results demonstrated the consistent detection of S. spallanzanii and B. neritina free-eDNA when these organisms were present in high abundance. Once organisms were removed, the free-eDNA signal exponentially declined, noting that free-eDNA persisted between 24-72 h. Results indicate that organism biomass, specimen characteristics (e.g., stress and viability), and species-specific biological differences may influence free-eDNA detectability. This study represents the first step in assessing the feasibility of direct-ddPCR technology for the detection of marine species. Our results provide information that could aid in the development of new technology, such as a field development of ddPCR systems, which could allow for automated continuous monitoring of targeted marine species, enabling point-of-need detection and rapid management responses.

Monitoring of non-indigenous marine species for legislative and policy goals in the UK

Globally, the ecological and socio-economic impacts of non-indigenous species (NIS) are increasingly recognised, prompting the development of international policies and legislation that aim to reduce these impacts. Monitoring programmes are required to assess compliance with legislation and progress towards management targets. However, monitoring programmes often need to fulfil the requirements of several legislative drivers, as well as adapt to changing political circumstances and environmental targets, and thereby face design and implementation challenges. In this paper, we summarise the current legislative drivers for monitoring of non-indigenous marine species and provide a review of existing monitoring in UK waters. This paper also discusses aspirations for NIS monitoring, outlines progress, and provides recommendations to address remaining gaps. While the focus is on the drivers for NIS monitoring in UK marine waters, the key messages, in particular recommendations for future improvements, are applicable on a global scale.

National assessment on the status, trends and impacts of marine non-indigenous species for the European Union marine strategy framework directive

The Marine Strategy Framework Directive (MSFD) of the European Union aims to enhance the protection of marine ecosystems by assessing Good Environmental Status using several descriptors. Descriptor 2 of the MSFD states that the status of marine non-indigenous species (NIS) should be assessed using specified criteria regarding newly introduced NIS, abundance, and spatial distribution of established NIS, as well as proportions of native species groups adversely altered due to NIS. The current study presents a national NIS indicator assessment for the six sub-basins associated with the Finnish marine waters. The study additionally aimed to develop a methodology to assess changes in native species communities over time. A new biodiversity index was created for this purpose by combining the Gini-Simpson index, and species and phyla richness into a Community Biodiversity Index (CBI). CBI was calculated to measure changes in biodiversity within the soft-bottom benthic communities of the study area, and correlation analyses were conducted between the index scores and NIS proportion. Overall, 34 NIS have been recorded from the Finnish marine waters by 2022, and more than half of them have arrived since 1992. Spatial distribution of three established non-indigenous taxa (Marenzelleria spp., Cercopagis pengoi and Neogobius melanostomus) has expanded during the latest assessment periods and nowadays cover most of the national marine waters. Meanwhile, abundance of Marenzelleria spp. in benthic communities has increased heavily in most sub-basins. The study outcomes indicated that NIS proportion correlated significantly with the CBI within the soft-bottom benthic communities. This correlation was significantly negative for the samples with a higher NIS proportion than the median, suggesting that when NIS became more dominant, biodiversity of the communities decreased. The current study provides an applicable method to evaluate changes in biodiversity for various species groups, and how to link them to changes in the distribution and abundance of established NIS. It can be concluded that the national biological monitoring program has severe temporal and spatial gaps, as the national monitoring data enabled the assessment on native species groups, adversely altered due to NIS to be completed only for one species group, soft-bottom macrozoobenthos. Most importantly, the study emphasised the crucial need for management actions to prevent further NIS introductions.

Exploring visual methods for monitoring marine non-indigenous species colonizing artificial structures in the Madeira archipelago (NE Atlantic)

The introduction of non-indigenous species (NIS) poses a significant threat to biodiversity in coastal communities globally, with maritime traffic serving as a primary vector for introducing these species into new habitats. Managing potential new marine invasions begins in harbours and marinas, where artificial structures are the first step towards establishing new habitats. In this study, we aimed to examine and compare the performance of three methods: Plate, Photo quadrate, and a new Video approach, using image analysis for monitoring fouling communities in artificial structures, with a specific focus on NIS in marinas. Additionally, we evaluated attributes for each method, including cost, area, deployment/sampling time, and logistics, to determine the most reliable, efficient, and affordable method with respect to species richness (S) and cover (N). The video (VID) method performed similarly to the plate (PLA) method in species identification and outperformed the photo (PHO) method. The VID method represents a novel and faster approach for monitoring NIS in artificial structures, offering several advantages. It allows data gathering that can be performed by non-taxonomic experts, facilitating rapid detection and intervention in managing marine invasions in port environments. By assessing the effectiveness of these methods, we sought to contribute to developing improved strategies and faster approaches for monitoring and mitigating the impact of NIS in coastal communities.

Marine Non-Indigenous Species Dynamics in Time and Space within the Coastal Waters of the Republic of Ireland

Documenting temporal and spatial occurrence trends of Non-Indigenous Species (NIS) is essential to understand vectors and pathways of introduction, and for horizon scanning for future introductions. This study provides an overview of marine NIS found in the Republic of Ireland up to 2020. Taxonomic groups, species origin, and location of first reporting (counties) were compiled and analysed focusing on the last three decades. While the unambiguous characterisation of introduction events is challenging, analysis of 110 species corroborated the global weight of evidence that shipping activities to/from ports and marinas are the most likely vectors and pathways in Ireland. A comparable review study for the Netherlands revealed that most NIS were first introduced to mainland Europe and subsequently would take on average >15 years to reach Ireland. In the last two decades there has been an increase in NIS-focused surveys in Ireland. Incorporating data from these surveys in centralized national repositories such as the National Biodiversity Data Centre, will strongly aid the evaluation of potential NIS management responses. Furthermore, the availability of robust baseline data as well as predictions of future invaders and their associated vectors and pathways will facilitate the effective application of emerging monitoring technologies such as DNA-based approaches.

Hurdles and opportunities in implementing marine biosecurity systems in data-poor regions.

Managing marine nonindigenous species (mNIS) is challenging, because marine environments are highly connected, allowing the dispersal of species across large spatial scales, including geopolitical borders. Cross-border inconsistencies in biosecurity management can promote the spread of mNIS across geopolitical borders, and incursions often go unnoticed or unreported. Collaborative surveillance programs can enhance the early detection of mNIS, when response may still be possible, and can foster capacity building around a common threat. Regional or international databases curated for mNIS can inform local monitoring programs and can foster real-time information exchange on mNIS of concern. When combined, local species reference libraries, publicly available mNIS databases, and predictive modeling can facilitate the development of biosecurity programs in regions lacking baseline data. Biosecurity programs should be practical, feasible, cost-effective, mainly focused on prevention and early detection, and be built on the collaboration and coordination of government, nongovernment organizations, stakeholders, and local citizens for a rapid response.

New species and new records of bryozoan species from fouling communities in the Madeira Archipelago (NE Atlantic)

Hull fouling is considered to be the most significant vector of introduction of marine non-indigenous species (NIS) in the Madeira Archipelago (NE Atlantic) because these islands provide a vital passage route for many ships. The transfer of species between boat hulls and artificial substrates in marinas is known to be high. Bryozoans are among the most common groups of marine invertebrates growing on this type of substrate. In recent years, significant advances have been made in our knowledge about the biodiversity of bryozoans in the Madeira Archipelago. Nonetheless, the currently recognized numbers remain far from reflecting the actual bryozoan species richness. In this context, we examine bryozoan samples stemming from NIS monitoring surveys on artificial substrates along the southern coast of the Madeira Archipelago, in four recreational marinas and in two offshore aquaculture farms. This has yielded new information about ten bryozoan species. Two of them, Crisia noronhai sp. nov. and Amathia maderensis sp. nov., are described for the first time, although at least the first one was previously recorded from Madeira but misidentified. Bugula ingens, Cradoscrupocellaria insularis, Scruparia ambigua, and Celleporaria brunnea are recorded for the first time in Madeira. Moreover, the material of C. brunnea was compared with the type, and a biometric analysis was performed with material from the Atlantic and Mediterranean. All samples identified as C. brunnea in both regions are the same species, and the variations described in the literature apparently reflect high intracolonial variability. Finally, we provide new information for the descriptions of 4 additional bryozoans, namely, Crisia sp. aff. elongata, Cradoscrupocellaria bertholletii, Scrupocaberea maderensis, and Tricellaria inopinata.

Non-Indigenous Species Dynamics in Time and Space within the Coastal Waters of The Netherlands

Information on temporal and spatial trends with regard to the introduction of non-indigenous species (NIS) is often sparsely available. These trends may potentially help improve the design and focus of monitoring programs, give insights into new pathways and hotspots, and facilitate horizon scanning. We provide an overview of 215 marine and brackish water NIS recorded in The Netherlands. Temporal trends over the most recent three decades for taxonomic groups, species origin, introduction vectors, and water systems were analysed. We attempt to explain the observed patterns and discuss factors that hamper their explanation. A shift in the region of origin from Pacific to W Atlantic can potentially be linked to legislation prohibiting Pacific oyster imports, whereas a subsequent shift backwards cannot. Case studies illustrate that NIS may not be first detected in the water systems where they were originally introduced. Additionally, it is shown that changes in allegedly native species’ distribution or seasonal pattern should be linked to an introduced cryptic NIS instead. We also discuss the shortcomings of monitoring programs that were originally not focused on NIS, the importance of naturalists’ observations, and the added value of a more recent network that is focused on NIS detection in the coastal waters of The Netherlands.

Flux of the Wetted Surface Area on Ships’ Hulls in Major Ports of Korea

Biofouling is a significant means for introducing non-indigenous marine species internationally, which can alter habitats and disturb marine ecosystems. This study estimated the flux of ships’ wetted surface area (WSA) to Korea in 2020 to assess the risks of biological invasion via biofouling on ships’ hulls. The annual total WSA flux entering Korea was estimated to be 418.26 km2, with short-stay vessels (<3 weeks) contributing to 99.7% of the total WSA flux. Busan and Ulsan ports were identified as the main sources of high-risk flux, with container ships being a major vector in Busan and tankers in Ulsan. Gwangyang port had the third-highest total WSA flux, with nearly half of the flux driven from coastwise voyages, making it particularly vulnerable to the spread of hull fouling organisms. These findings could help enhance the management and inspection of hull fouling organisms in Korea.

Pest Alert Tool-a web-based application for flagging species of concern in metabarcoding datasets.

Advances in high-throughput sequencing (HTS) technologies and their increasing affordability have fueled environmental DNA (eDNA) metabarcoding data generation from freshwater, marine and terrestrial ecosystems. Research institutions worldwide progressively employ HTS for biodiversity assessments, new species discovery and ecological trendmonitoring. Moreover, even non-scientists can now collect an eDNA sample, send it to a specialized laboratory for analysis and receive in-depth biodiversity record from a sampling site. This offers unprecedented opportunities for biodiversity assessments across wide temporal and spatial scales. The large volume of data produced by metabarcoding also enables incidental detection of species of concern, including non-indigenous and pathogenic organisms. We introduce an online app-Pest Alert Tool-for screening nuclear small subunit 18S ribosomal RNA and mitochondrial cytochrome oxidase subunit I datasets for marine non-indigenous species as well as unwanted and notifiable marine organisms in New Zealand. The output can be filtered by minimum length of the query sequence and identity match. For putative matches, a phylogenetic tree can be generated through the National Center for Biotechnology Information's BLAST Tree View tool, allowing for additional verification of the species of concern detection. The Pest Alert Tool is publicly available at https://pest-alert-tool-prod.azurewebsites.net/.

Testing differences of marine non-indigenous species diversity across Macaronesia using a standardised approach

The introduction of non-indigenous species (NIS) induces severe impacts on marine biodiversity and ecosystems. Macaronesia is an ecologically relevant region where several NIS were detected recently. For the first time, a standard experimental approach was designed to examine biofouling assemblages and investigate NIS across the region. In this context, sessile biofouling assemblages were examined in four recreational marinas in all the Macaronesian archipelagos from 2018 to 2020: the Azores, Madeira, Canary Islands, and Cabo Verde. We hypothesised that NIS numbers, abundance, and recruitment differed in each location due to abiotic and biotic features. From the Azores (higher latitudes) to Cabo Verde (lower latitudes), NIS recruitment and percentage cover decreased following a partial latitude gradient. The present study unveiled 25 NIS, with new records for the Azores (two cryptogenic species), Canary Islands (one NIS and two cryptogenic species), and Cabo Verde (three NIS and three cryptogenic species). The present research represents a pioneer and relevant step in advancing our current understanding of marine biological invasions in Macaronesia, employing a standard and low-cost approach.

Biofouling occlusion of ships’ internal seawater systems: operational, economic, and biosecurity consequences

Biofouling of ships’ internal seawater systems (ISS) can cause significant operational issues and is a potential transfer mechanism for marine nonindigenous species. This study used an engine room simulator and economic evaluation to quantify impacts on commercial ship performance of biofouling occlusion within various ISS nodes (sea chest, strainer, and heat exchangers). A characteristic hockey-stick relationship between occlusion and impact emerged, whereby engine room systems could tolerate up to 55% occlusion of a single node without operational impact, followed by rapid performance deterioration. The relative magnitude of impacts varied by ISS node and in response to changes in ambient seawater temperatures. System tolerance was much lower when simultaneous occlusion of multiple nodes was assessed. In economic terms, consequences included required freight rate increases of 1–26% prior to forced (automatic) slowdown of the ship and up to 82% increases if slowdown conditions were required.

Harnessing decay rates for coastal marine biosecurity applications: A review of environmental DNA and RNA fate

AbstractMarine nonindigenous species (NIS) are spreading at an alarming rate internationally through anthropogenic activities such as shipping and aquaculture, affecting local biodiversity and negatively impacting the ecosystem and human well‐being. Countries and international organizations have recognized this global threat and have begun implementing biosecurity management programs to ensure early detection, effective surveillance, and mitigation of marine NIS spread. Molecular techniques based on environmental DNA and RNA (eDNA/eRNA), collectively referred to as environmental nucleic acids (eNAs), have become a popular noninvasive tool for detecting NIS and monitoring biodiversity locally and globally. However, uncertainties about eNAs detection probabilities and the location of the source population impede the broad uptake of this tool in marine biosecurity programs. It's been hypothesized that most of these uncertainties can be explained by studying the molecules' dynamics within a marine environment and implementing eNAs distribution models. To contribute to further knowledge development in this area, our study reviews data from 20 recent reports on the degradation mechanisms and fate of eNAs in the marine environment. We classified the critical factors influencing eNAs' persistence that should be considered by biosecurity practitioners, outlining the complex interaction between the molecules' degradation processes and particular environmental conditions. To help guide the parameterization of eNAs distribution models, this review also summarizes and standardizes the marine decay rates of eDNA/eRNA from the literature. Finally, this manuscript outlines guidelines to help calculate accurate decay rates to build appropriate “fit‐for‐purpose” marine biosecurity tools for improved target detectability and greater resolution in assessing biodiversity.

Towards remote surveillance of marine pests: A comparison between remote operated vehicles and diver surveys

Early detection of marine invasive species is key for mitigating and managing their impacts to marine ecosystems and industries. Human divers are considered the gold standard tool for detecting marine invasive species, especially when dive teams are familiar with the local biodiversity. However, diver operations can be expensive and dangerous, and are not always practical. Remote operated vehicles (ROVs) can potentially overcome these limitations, but it is unclear how sensitive they are compared to trained divers for detecting pests. We assessed the sensitivity and efficiency of ROVs and divers for detecting marine non-indigenous species (NIS), including the potential for automated detection algorithms to reduce post-processing costs of ROV methods. We show that ROVs can detect comparable assemblages of invasive species as divers, but with lower detection rates (0.2 NIS min-1) than divers (0.5 NIS min-1) and covered less seafloor than divers per unit time. While small invertebrates (e.g., skeleton shrimp Caprella mutica) were more easily detected by divers, the invasive goby Acentrogobius pflaumii was only detected by the ROV. We show that implementation of computer vision algorithms can provide accurate identification of larger biofouling organisms and reduce overall survey costs, yet the relative costs of ROV surveys remain almost twice that of diver surveys. We expect that as ROV technologies improve and investment in autonomous and semi-autonomous underwater vehicles increases, much of the current inefficiencies of ROVs will be mitigated, yet practitioners should be aware of limitations in taxonomic resolution and the strengths of specialist diver teams.

Prioritizing management of high-risk routes and ports by vessel type to improve marine biosecurity efforts

The shipping industry constitutes the main vector of marine bioinvasions. Over 90,000 vessels world-wide create a highly complex shipping network that requires appropriate management tools. Here we characterized a novel vessel category, Ultra Large Container Vessels (ULCV), in terms of potential contribution to the dispersal of Non-Indigenous Species (NIS) in comparison to smaller vessels traveling similar routes. Such approach is essential for providing precise information-based risk analysis necessary to enforce biosecurity regulations and reduce the adverse global effects of marine NIS. We used Automatic Identification System (AIS) based websites to extract shipping data that will enable us to test for differences in two vessel behaviors linked to NIS dispersal: port visit durations and voyage sailing times. We then examined the geographic spread of ULCVs and small vessels, quantifying the accumulation of new port visits, countries, and ecoregions for each vessel category. Finally, Higher Order Network (HON) analysis revealed emergent patterns within shipping traffic, species flow, and invasion risk networks of these two categories. Compared to the smaller vessels, ULCVs spent significantly longer time in 20% of the ports and were more geographically constrained, with fewer port visits, countries, and regions. HON analysis revealed that the ULCV shipping species flow and invasion risk networks were more similar to each other than to those of the smaller vessels. However, HON port importance shifts were discernible for both vessel categories, with major shipping hubs not necessarily being major invasion hubs. Overall, compared to smaller vessels, ULCVs behave differently in ways that potentially increase biofouling risk, albeit in a smaller set of ports. Future studies using HON analysis of other dispersal vectors appears critical for prioritizing management of high-risk routes and ports.

Citizen Science and Expert Judgement: A Cost-Efficient Combination to Monitor and Assess the Invasiveness of Non-Indigenous Fish Escapees

Mapping the distribution and evaluating the impacts of marine non-indigenous species (NIS) are two fundamental tasks for management purposes, yet they are often time consuming and expensive. This case study focuses on the NIS gilthead seabream Sparus aurata escaped from offshore farms in Madeira Island in order to test an innovative, cost-efficient combined approach to risk assessment and georeferenced dispersal data collection. Species invasiveness was screened using the Aquatic Species Invasiveness Screening Kit (AS-ISK), and revealed a high invasion risk. Occurrences of S. aurata were assessed involving citizens in GIS participatory mapping and data from recreational fishing contests. A probability map showed that S. aurata is well dispersed around Madeira Island. This assessment proved to be a cost-efficient early warning method for detecting NIS dispersal, highlighting the urgent need for additional surveys that should search for sexually mature individuals and assess the direct and indirect impacts in the native ecosystem.

An Overview of Marine Non-Indigenous Species Found in Three Contrasting Biogeographic Metropolitan French Regions: Insights on Distribution, Origins and Pathways of Introduction

Biological invasions are one of the main global threats to biodiversity in terrestrial, freshwater and marine ecosystems worldwide, requiring effective inventorying and monitoring programs. Here, we present an updated list of non-indigenous species in French marine and transitional waters. Focused on eukaryote pluricellular species found throughout the three metropolitan French marine regions (Western Mediterranean Sea, Bay of Biscay and the Northern Seas), a total of 342 non-indigenous, including 42 cryptogenic, species are listed as having been introduced since the 13th century. The majority of the species originated from the temperate Northern Pacific. They mainly arrived through both ballast and hull fouling and also are associated with shellfish farming activities. Most of them have been introduced since the 1970s, a time when maritime and aquaculture trade intensified. Despite important human-aided opportunities for species transfer between the three marine regions (for instance, via recreational boating or aquaculture transfers), only a third of these NIS are common to all regions, as expected due to their environmental specificities.