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Fisheries-dependent data and information gathered through fisheries-related scientific surveys can significantly contribute to research on the patterns and processes underlying marine biological invasions and their interactions with fisheries. This study presents an overview of the presence of non-native fish species in the North Aegean Sea, offering insights into their distributions and impact on fisheries. The findings are based on a comprehensive compilation of commercial fisheries-dependent and scientific survey data collected in Greece from 2016 to 2023, along with a systematic review of the international scientific literature. The study resulted in the documentation of the presence of 37 nonnative fish species, including several recorded for the first time in the area. The results suggest that non-native fish species invasions in the North Aegean Sea are dynamic. Although most species were classified as casual, and the frequencies of occurrence as well as the quantities in commercial fisheries catches of established species are smaller than in the South Aegean Sea, species introductions and the extent of occurrence and area of occupancy of several species have been increasing since the 2000s. The significance of non-native fish species is becoming increasingly relevant to commercial fisheries in the study area. This is particularly evident in the Northeastern Aegean Sea, where catches of non-native species are on the rise, and new species with potential commercial value have emerged in recent years. [ABSTRACT FROM AUTHOR]

The brown seaweed Rugulopteryx okamurae (Dictyotales, Ochrophyta), native to the Pacific Ocean and widely distributed in Asia, has been recently recognized as an emblematic case of biological invasion by marine macroalgae in European waters. Since 2015 and from the Strait of Gibraltar, R. okamurae has rapidly spread towards Atlantic and Mediterranean coastal areas exhibiting an invasive behaviour with significant ecological and socio-economic impacts. Here, we report the first morphologically and genetically confirmed observation of this species in Italy, along the north-western coast of Sicily (Gulf of Palermo). Specimens were found as drifted material and as an established population on Posidonia oceanica, representing its new eastern distribution limit in the Mediterranean Sea, as the species was previously established in Marseilles (France). Furthermore, we performed a favorability distribution model with the current introduced distribution of the species for the Mediterranean, which shows most of the western Mediterranean, including the Balearic archipelago, Corsica and Sardinia, central Mediterranean, including Sicily, and the northern coast of Africa together with eastern Mediterranean basin, as highly favorable for R. okamurae. The most probable vectors for this introduction are sea currents and maritime traffic, including fishing activities. This hypothesis was supported by some of the ranked variables in the favorability model, i.e., current velocity, and the proximity of the introduced population to fishing ports. These results are a warning that the species can cover large sea distances via sea currents, thus also threatening the ecosystems and marine resources of the central and eastern Mediterranean Sea, as these areas are forecasted to be highly favorable regions for the species. We suggest coordinated actions at the European level with stakeholders in the fishing sector regarding prevention, both because it is a highly affected sector and because it potentially has a very important role in the dispersion of the species. [ABSTRACT FROM AUTHOR]

Three intertidal varunid crab species of the genus Hemigrapsus , viz. H. penicillatus , H. sanguineus , and H. takanoi , are widely distributed along the East Asian coastline. The first two became globally well-known after their introduction into Atlantic waters of North America and Europe. Since the first record in the late 1980s, they established breeding populations and now live in sympatry with native and other invasive crab species. The aim of this study was to determine the correct species identity and geographic origin of these invasive populations and, if possible, estimate the number of independent invasion events. For that purpose, specimens from the three species were obtained from native populations in Taiwan, Japan, Russia, Korea, and China, and genetically compared to invasive populations from Europe and the U.S.A. Sequences of the mitochondrial cytochrome c oxidase subunit I gene were generated and used for haplotype network and AMOVA analyses, thus providing insights into the potential invasion pathways, gene flow, and phylogeography of the two invasive species. Pronounced geographic structure for all three species is revealed in their native ranges, with a marked differentiation among northern and southern populations. We furthermore provide evidence that all invasions into North America and Europe originated from northern Asian populations, which is in line with similar climatic conditions in Europe, northeastern America and northern Asia. Our results also confirm the recent finding that all European populations previously thought to consist of H. penicillatus should be reclassified as H. takanoi. [ABSTRACT FROM AUTHOR]

The article offers information on a one-day consultative meeting held last year on collaborative strategies for managing aquatic biological invasions. It discusses the significance of studying biological invasions, especially in aquatic ecosystems, due to their threats to biodiversity and livelihoods. Topics include the participation of experts, policymakers, and stakeholders from various organizations, the objectives of the meeting, and the significance of understanding.

The risks imposed by biological invasions on marine ecosystems are increasing worldwide. The mud crab Rhithropanopeus harrisii has recently expanded its distribution to the northeastern Baltic Sea, where low predatory pressures and the absence of functionally similar competitors favored the establishment of the species. Few studies have addressed the effects of the mud crab on Baltic benthic communities and habitats. Even fewer have looked at the consequences of the invader on habitats dominated by Fucus vesiculosus, the main habitat-forming macrophyte in the Baltic Sea. The present study experimentally analyzed, under laboratory conditions, the effects of R. harrisii on Baltic F. vesiculosus habitats and associated communities under different temperatures simulating summer and winter regimes. Our results show that the effects of the mud crab are modulated by temperature, being more pronounced under summer conditions when the metabolic demands and food intake requirements are higher. The experiment provided new insights into the capacity of R. harrisii to disrupt recruitment in native snail populations, jeopardizing the persistence of healthy populations of key grazers in F. vesiculosus habitats. Moreover, our results conclusively demonstrated the capacity of the invader to decimate native blue mussel populations. The impacts on functionally relevant invertebrates can have far-reaching ecological consequences, altering the food web and disrupting entire coastal ecosystems in the Baltic Sea. [ABSTRACT FROM AUTHOR]

Biological invasions have become a defining feature of marine Mediterranean ecosystems with significant impacts on biodiversity, ecosystem services, and human health. We systematically reviewed the current knowledge on the impacts of marine biological invasions in the Mediterranean Sea. We screened relevant literature and applied a standardised framework that classifies mechanisms and magnitude of impacts and type of evidence. Overall, 103 alien and cryptogenic species were analysed, 59 of which were associated with both negative and positive impacts, 17 to only negative, and 13 to only positive; no impacts were found for 14 species. Evidence for most reported impacts (52%) was of medium strength, but for 32% of impact reports evidence was weak, based solely on expert judgement. Only 16% of the reported impacts were based on experimental studies. Our assessment allowed us to create an inventory of 88 alien and cryptogenic species from 16 different phyla with reported moderate to high impacts. The ten worst invasive species in terms of reported negative impacts on biodiversity include six algae, two fishes, and two molluscs, with the green alga Caulerpa cylindracea ranking first. Negative impacts on biodiversity prevailed over positive ones. Competition for resources, the creation of novel habitat through ecosystem engineering, and predation were the primary reported mechanisms of negative effects. Most cases of combined negative and positive impacts on biodiversity referred to community-level modifications. Overall, more positive than negative impacts were reported on ecosystem services, but this varied depending on the service. For human health, only negative impacts were recorded. Substantial variation was found among Mediterranean ecoregions in terms of mechanisms of impact and the taxonomic identity of impacting species. There was no evidence that the magnitude of impact increases with residence time. Holistic approaches and experimental research constitute the way forward to better understanding and managing biological invasions. [ABSTRACT FROM AUTHOR]

The invasive macroalga Caulerpa cylindracea has spread widely in the Mediterranean Sea, becoming a favorite food item for native fish for reasons yet unknown. By using a combination of behavioral, morphological, and molecular approaches, herein we provide evidence that the bisindole alkaloid caulerpin, a major secondary metabolite of C. cylindracea, significantly increases food intake in the model fish Danio rerio, influencing the regulation of genes involved in the orexigenic pathway. In addition, we found that the compound improves fish reproductive performance by affecting the hypothalamus–pituitary–gonadal axis. The obtained results pave the way for the possible valorization of C. cylindracea as a sustainable source of a functional feed additive of interest to face critical challenges both in aquaculture and in human nutrition. [ABSTRACT FROM AUTHOR]

Human-induced pressures have led to substantial changes in marine ecosystems worldwide, with the introduction of non-indigenous species (NIS) emerging as a significant threat to ecological, economic, and social aspects. The Macaronesian islands, comprising the Azores, Madeira, Canary Islands, and Cabo Verde archipelagos, are regions where the regional economy is dependent on marine resources (e.g., marine traffic, ecotourism and fisheries). Despite their importance, concerted efforts to manage marine biological invasions in Macaronesia have been scarce. In this context, the current study aims to contribute to the much-needed debate on biosecurity measures in this unique insular ecosystem to prevent and mitigate the impact of NIS. By adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria, this work validated and analyzed 260 documents providing insights into the management of NIS in Macaronesia until 2022. These documents revealed the presence of 29 Invasive Alien Species (IAS), most of which are misconceptions regarding this terminology. Most studies focused on the stages of early detection, rapid response, and eradication across the archipelagos. Cabo Verde had comparatively fewer studies. The most common techniques include monitoring/sampling, literature reviews, and taxonomic reviews. NIS introduction pathways were mainly attributed to transport (stowaway) and unaided migration, with ship fouling, ballast water, rafting, ocean currents, and tropicalization being also identified as significant contributors. This systematic review highlights the current efforts to establish robust biosecurity protocols in Macaronesia and emphasizes the urgent need to safeguard the region's ecological, economic, and social well-being. • First systematic review regarding management of non-indigenous species in Macaronesia. • 260 documents providing insights into the management of NIS in Macaronesia until 2022. • 29 Invasive Alien Species (IAS) were detected, most of which are misconceptions regarding this terminology. • NIS introduction pathways were mainly attributed to transport (stowaway) and unaided migration. • This study highlights the current efforts to establish robust biosecurity protocols in Macaronesia. [ABSTRACT FROM AUTHOR]

Aims: The present study is the first attempt to grasp the scale and richness of marine biological invasions in Macaronesia. We pioneered a comprehensive non‐native species (NNS), inventory in the region to determine their diversity patterns and native distribution origins. NNS were defined here as the result of both introductions and range expansions. We also used statistical modelling to examine relationships among NNS richness, anthropogenic activities, demographic and geographical variables across Macaronesia. Location: Macaronesia. Methods: A comprehensive literature search was conducted for marine NNS records in Macaronesia, registering the first record's location and year from 1884 to 2020. We used univariate and multivariate analyses to evaluate differences and similarities in community composition. By applying a Generalized Linear Model (GLM), we tested hypotheses regarding NNS richness as a function of anthropogenic activities, demographic and geographical variables. Results: A total of 144 marine non‐native species (NNS) were recorded for the whole of Macaronesia. The highest NNS richness was registered in the Canary Islands (76 NNS), followed by the Azores (66 NNS), Madeira (59 NNS) and finally Cabo Verde (18 NNS). Some differences amongst archipelagos were observed, such as the high number of non‐native macroalgae in the Azores, fishes in the Canary Islands and tunicates in Cabo Verde. Overall, macroalgae, tunicates and bryozoans were the predominant taxonomic groups in the Macaronesian archipelagos. Madeira and Canary Islands were the archipelagos with more similarity in marine NNS, and Cabo Verde the most divergent. Finally, GLM suggested that non‐native richness patterns across Macaronesia were dependent on the considered archipelago and strongly affected by (1) minimum distance to the mainland, (2) the total number of ports and marinas and (3) total marinas area (km2). Conclusions: The model results and NNS listing in the present study will likely raise the awareness and response regarding marine NNS in the whole Macaronesia region, serving as a baseline for future research as well as implementing and enforcing regulations related to the introduction of marine NNS in oceanic islands. [ABSTRACT FROM AUTHOR]

The knowledge of biotic and abiotic drivers that put non-native invasive fishes at a disadvantage to native ones is necessary for suppressing invasions, but the knowledge is scarce, particularly when abiotic changes are fast. In this study, we increased this knowledge by an analysis of the biomass of most harmful Prussian carp Carassius gibelio in a river reviving from biological degradation. The species' invasion followed by the invasion's reversal occurred over only two decades and were documented by frequent monitoring of fish biomass and water quality. An initial moderate improvement in water quality was an environmental filter that enabled Prussian carp's invasion but prevented the expansion of other species. A later substantial improvement stimulated native species' colonization of the river, and made one rheophil, ide Leuciscus idus, a significant Prussian carp's replacer. The redundancy analysis (RDA) of the dependence of changes in the biomass of fish species on water quality factors indicated that Prussian carp and ide responded in a significantly opposite way to changes in water quality in the river over the study period. However, the dependence of Prussian carp biomass on ide biomass, as indicated by regression analysis and analysis of species traits, suggests that the ecomorphological similarity of both species might have produced interference competition that contributed to Prussian carp's decline. [ABSTRACT FROM AUTHOR]

The invasive macroalga Caulerpa cylindracea has spread widely in the Mediterranean Sea, becoming a favorite food item for native fish for reasons yet unknown. By using a combination of behavioral, morphological, and molecular approaches, herein we provide evidence that the bisindole alkaloid caulerpin, a major secondary metabolite of C. cylindracea, significantly increases food intake in the model fish Danio rerio, influencing the regulation of genes involved in the orexigenic pathway. In addition, we found that the compound improves fish reproductive performance by affecting the hypothalamus–pituitary–gonadal axis. The obtained results pave the way for the possible valorization of C. cylindracea as a sustainable source of a functional feed additive of interest to face critical challenges both in aquaculture and in human nutrition.

We devised a practical method for integrating information on 2 marine invasive species using 3 different approaches: standardized ecological monitoring, online‐reporting databases, and surveys of anglers and crabbers. Focusing on 2 recently introduced species with different characteristics, the Asian shore crab (Hemigrapsus sanguineus) and Chinese mitten crab (Eriocheir sinensis), in the Hudson‐Raritan watershed of New York and New Jersey, we used sensitivity analyses to explore the relative contribution of each information source to knowledge of species abundance and distribution. All 3 information sources contributed something unique to understanding abundance and distribution of the introduced crabs. Online and survey data on Asian shore crabs significantly affected predictions of abundance, whereas monitoring data did not. When survey data were omitted, abundance estimates were unchanged over time, but when they were included, the model predicted an increased abundance in 2012. All 3 data sets for the Asian shore crab significantly affected estimates of species coverage; surveys had the biggest influence, increasing range size by 4097.25 km2. For the catadromous Chinese mitten crab, ecological monitoring data collected in freshwater shortly after the original sighting significantly shaped model estimates for abundance and documented the establishment phase of the mitten crab in an area outside the spatial scope of the surveyed resource users. However, the survey data significantly enlarged mitten crab range‐size estimates by 6498.01 km2. By demonstrating that data integration produced an image of the invasion process that would not have emerged had we used any 1 method individually, model results provide evidence for the advantages of an interdisciplinary approach. Article impact statement: Information sharing across information domains improves the understanding of invasion trends. [ABSTRACT FROM AUTHOR]

Invasive species threaten worldwide biodiversity. Success in facing this problem may be possible through the engagement of younger audiences. Here, a game was designed to teach children how to recognize invasive seaweed and to encourage them to participate in marine citizen science. The game was first tested in a pilot study, and then carried out in Salinas High School (Asturias, Spain). Game-based training consisted of an explanation of invasive species, followed by the 'Find invasive seaweed' game and was evaluated with tests before and after the activity. After training, students spent 3 months looking for invasive species. Four invasive species were detected in the study area. The results showed a positive impact on knowledge gains and significant differences in marine environmental awareness and conservation actions. [ABSTRACT FROM AUTHOR]

Parupeneus forsskali has been the latest Indo-Pacific goatfish species to expand its range into the Mediterranean. It is the least studied alien mullid in the Eastern Mediterranean, and specific information on its diet is generally lacking in the literature. The objectives of this paper are (1) to comprehensively document the progress of its invasion in the Mediterranean through a systematic literature review to retrieve all published records of the species in the region, and (2) to present preliminary quantitative information on its diet in its non-native range. Parupeneus forsskali, first recorded in Cyprus in 2014, has established self-sustaining, reproducing, commercially important populations in the nearshore waters of Cyprus at least since 2017. Significant P. forsskali catches by artisanal fisheries in Cyprus began in late 2017 and have been increasing since. Its particularly successful establishment and spread across Cyprus occurred after a time lag of several years since its introduction in the Mediterranean, possibly during the 1990s or earlier. As the westernmost records of the species along both the southern and the northern Mediterranean coastlines were made in recent years, it is assumed that P. forsskali is currently expanding its range in the Mediterranean. The prey items identified in the stomach contents analysis, ranked by their frequency of occurrence, belonged to the following taxonomic groups: Crustacea (67%), Mollusca (37%), Polychaeta (19%), Foraminifera (12%), Actinopterygii (5%). [ABSTRACT FROM AUTHOR]

Aim: The development of approaches to predict the distribution and potential expansion of invasive species is still an open challenge. Here our goal is to improve the modelling procedure for marine invaders by coupling Species Distribution Models (SDMs) with an analysis of their univariate niche dynamics. In particular, we tested for the first time whether choosing model predictors among the stable niche dimensions was effective in improving predictions of invasive species expansion. Location: Mediterranean Sea. Taxon: Dusky spinefoot, Siganus luridus. Methods: We analysed the univariate niche dynamics for S. luridus across its native and invaded ranges, by applying a standardized framework that allowed the identification of cases of niche stability or shift. We compared inter‐range transferability of SDMs fitted with different combinations of labile or stable predictors. Finally, we evaluated interactions in SDM settings (calibration area, model technique and predictors set) on models' predictive ability, using independent data from the most recent phase of invasion. Results: We detected a pattern of niche stability for several variables, especially salinity and bathymetry, which positively influenced model inter‐ranges transferability: when the models calibrated in the native range include only stable niche axes, predictive ability is improved. We also identified a shift towards lower surface temperatures in the introduced range, which were almost never experienced by the species before invasion. The model calibrated within the combined ranges was the most ecologically congruent. Also, models calibrated in the invaded range allowed a correct prediction of range expansion, with the predicted suitable areas only slightly underestimated. Main conclusions: We provide the first evidence that using conserved predictors in SDMs improves inter‐range projections of expanding invasive species. Variable selection, calibration area and modelling technique all matter when modelling invasive species, with important interaction effects. We provide guidelines on how to improve SDMs applications in biological invasion research. [ABSTRACT FROM AUTHOR]

The first comprehensive survey of marine bioinvasions in the southern Southwest Atlantic Ocean (SWA, ca. 33°45'-ca. 54°50'S) published in 2002 reported 31 introduced and 46 cryptogenic species. In this assessment, we update this work by providing a deep historical perspective of marine biological invasions as well as a full new review of introductions that have occurred over the past nearly two decades. We reviewed a variety of sources including peer-reviewed journals and monographs, government reports, and museum databases, among others. The previous survey was re-evaluated and taxonomic experts were also consulted. For each species, the possible status as introduced or cryptogenic, likely vector, likely native region, first collection date if known, and the first authoritative reference of its SWA occurrence were determined. Species were categorized by biogeographical provinces. Our reevaluation of species status lowered the 2002 survey to 29 introduced and 29 cryptogenic species. The result of our analyses added 100 new introduced and 43 new cryptogenic species, making a total of 129 introduced and 72 cryptogenic marine species for the SWA. Of these 100 species, 67 were found in the literature older than the 2002 survey, and 33 were found as new invasions that occurred since 2002, averaging one new invasion every 178 days. Ships are the most likely vector of invasions with an additional few species introduced with aquaculture, for ornamental purposes or for stabilizing coastal dunes. Most species are native to either the North Pacific or North Atlantic Oceans. Most introduced species (51%) occur in the warm temperate SWA marine ecoregion, while fewer (16%) occur in the cold temperate Magellanic marine ecoregion. Since ships are the main vectors in the region, we forecast that new introductions will continue until regional and international regulations to control ballast water and hull fouling begin to be effective. Our results urge the creation of long-term assessment programs focused on marine coastal biodiversity as a way to avoid inefficient environmental management based on deficient baseline information. [ABSTRACT FROM AUTHOR]

Antarctica is experiencing significant ecological and environmental change, which may facilitate the establishment of non‐native marine species. Non‐native marine species will interact with other anthropogenic stressors affecting Antarctic ecosystems, such as climate change (warming, ocean acidification) and pollution, with irreversible ramifications for biodiversity and ecosystem services. We review current knowledge of non‐native marine species in the Antarctic region, the physical and physiological factors that resist establishment of non‐native marine species, changes to resistance under climate change, the role of legislation in limiting marine introductions, and the effect of increasing human activity on vectors and pathways of introduction. Evidence of non‐native marine species is limited: just four marine non‐native and one cryptogenic species that were likely introduced anthropogenically have been reported freely living in Antarctic or sub‐Antarctic waters, but no established populations have been reported; an additional six species have been observed in pathways to Antarctica that are potentially at risk of becoming invasive. We present estimates of the intensity of ship activity across fishing, tourism and research sectors: there may be approximately 180 vessels and 500+ voyages in Antarctic waters annually. However, these estimates are necessarily speculative because relevant data are scarce. To facilitate well‐informed policy and management, we make recommendations for future research into the likelihood of marine biological invasions in the Antarctic region. [ABSTRACT FROM AUTHOR]

The European noble crayfish Astacus astacus is threatened by crayfish plague caused by the oomycete Aphanomyces astaci, which is spread by the invasive North American crayfish (e.g. signal crayfish Pacifastacus leniusculus). Surveillance of crayfish plague status in Norway has traditionally relied on the monitoring survival of cage‐held noble crayfish, a method of ethical concern. Additionally, trapping is used in crayfish population surveillance. Here, we test whether environmental DNA (eDNA) monitoring could provide a suitable alternative to the cage method, and a supplement to trapping.We took advantage of an emerging crayfish plague outbreak in a Norwegian watercourse following illegal introduction of disease‐carrying signal crayfish, and initiated simultaneous eDNA monitoring and cage‐based surveillance, supplemented with trapping. A total of 304 water samples were filtered from several sampling stations over a 4‐year period. eDNA data (species‐specific quantitative real‐time PCR [qPCR]) for the presence of A. astaci, noble and signal crayfish within the water samples were compared to cage mortality and trapping.This is the first study comparing eDNA monitoring and cage surveillance during a natural crayfish plague outbreak. We show that eDNA monitoring corresponds well with the biological status measured in terms of crayfish mortality and trapping results. eDNA analysis also reveals the presence of A. astaci in the water up to 2.5 weeks in advance of the cage method. Estimates of A. astaci and noble crayfish eDNA concentrations increased markedly during mortality and vanished quickly thereafter. eDNA provides a snapshot of the presence, absence or disappearance of crayfish regardless of season, and constitutes a valuable supplement to the trapping method that relies on season and legislation.Synthesis and applications. Simultaneous eDNA monitoring of Aphanomyces astaci (crayfish plague) and relevant native and invasive freshwater crayfish species is well‐suited for early warning of invasion or infection, risk assessments, habitat evaluation and surveillance regarding pathogen and invasive/native crayfish status. This non‐invasive, animal welfare friendly method excludes the need for cage‐held susceptible crayfish in disease monitoring. Furthermore, eDNA monitoring is less likely to spread A. astaci than traditional methods. This study resulted in the implementation of eDNA monitoring for Norwegian crayfish plague and crayfish surveillance programmes, and we believe other countries could improve management strategies for freshwater crayfish using a similar approach. Simultaneous eDNA monitoring of Aphanomyces astaci (crayfish plague) and relevant native and invasive freshwater crayfish species is well‐suited for early warning of invasion or infection, risk assessments, habitat evaluation and surveillance regarding pathogen and invasive/native crayfish status. This non‐invasive, animal welfare friendly method excludes the need for cage‐held susceptible crayfish in disease monitoring. Furthermore, eDNA monitoring is less likely to spread A. astaci than traditional methods. This study resulted in the implementation of eDNA monitoring for Norwegian crayfish plague and crayfish surveillance programmes, and we believe other countries could improve management strategies for freshwater crayfish using a similar approach. [ABSTRACT FROM AUTHOR]

Abstract Shipping is understood to be a major vector for the introduction and spread of marine non-indigenous species (NIS). However, recreational boating is still unregulated and its influence as vector has not yet been assessed for the Mediterranean Sea, which is the second most popular recreational boating destination worldwide. This is the first large-scale study to examine this by a combined biological (analyzing hull and marina fouling) and social approach (boaters surveys on maintenance habits, travel patterns and awareness), focused on peracarid crustaceans. A surprisingly high number of NIS were found on vessels cruising Mediterranean waters, and species compositions suggest an exchange between marina and vessel assemblages. This means recreational boating presents a risk for NIS spread which should warrant regulation. Results also implied that regionally coordinated management should be supported by effective local-scale-based management in the Mediterranean, which could improve upon with targeted environmental education to solve lack of awareness. Highlights • This study examines boating as a vector of non-indigenous species (NIS) introductions. • Specifically, peracarid crustaceans are studied in marinas and boats in the Mediterranean. • Results show numerous NIS in marinas and vessels and suggest exchanges between them. • Vessel maintenance and travel patterns influence the likelihood of NIS occurrence. • There is a general lack of awareness of marine bioinvasions among recreational boaters. [ABSTRACT FROM AUTHOR]

We report new localities for Callinectes sapidus in the Iberian Peninsula that widen the north-eastern limit of its distribution by more than 206 km along the Iberian Mediterranean coastline. This invasive species has been captured in the estuaries of the Fluvià, Muga and Ter rivers and has become established in the Fluvià River in only nine months since the first individual was detected. These reports show how rapid expansion of C. sapidus can be and that this may be preceded by the presence of isolated individuals. [ABSTRACT FROM AUTHOR]

Climate change is impacting environmental conditions, especially with respect to temperature and ice cover in high latitude regions. Predictive models and risk assessment are key tools for understanding potential changes associated with such impacts on coastal regions. In this study relative ecological risk assessment was done for future potential introductions of three species in the Canadian Arctic: periwinkle Littorina littorea, soft shell clam Mya arenaria and red king crab Paralithodes camtschaticus. These species occur in locations connected to Canadian Arctic ports through shipping and have the potential to be introduced via ballast water discharge. The methodology proposed in this study is unique in the sense that it considers not only ballast water origin, but also the distribution of the species being assessed and the sensitivity of the receiving habitat. It combines detailed information (ballast water source of each tank, transit time, time of the year when the water is released, environmental suitability of receiving habitat, impact, and habitat sensitivity) in order to assess ecological risk. Through the use of this approach it is highlighted that domestic discharge events pose a higher relative overall risk on a vessel-specific and cumulative annual bases than international discharges. The main ports of Deception Bay and Churchill were classified as being at moderate to high relative risk for L. littorea and M. arenaria, especially from domestic vessels, while relative overall risk for P. camtschaticus was low for international vessels and null for domestic vessels due to few ships transiting from its range of distribution to Canadian Arctic ports. This work can serve as an approach to help build a list of potential high risk species–a “grey” watch list–for the Canadian Arctic, and provides useful information for consideration in future decision making actions such as the identification of high risk pathways, species and ports. [ABSTRACT FROM AUTHOR]

The biomass of organisms of different sizes is increasingly being used to explore macroscale variation in food-web and community structure. Here we examine how invasive species and river flow regulation affect native fish biomass and fish community log10 biomass – body mass scaling relationships in Australia's largest river system, the Murray–Darling. The log10 biomass – body mass scaling exponent (scaling B) of invasive fishes (95% CI: −0.14 to −0.18) was less negative than for native fishes (95% CI: −0.20 to −0.25), meaning that invasive species attained a higher biomass in larger size-classes compared to native species. Flow alteration and invasive common carp (Cyprinus carpio) biomass were correlated with severe reductions in native fish biomass ranging from −47% to −68% (95% CI). Our study provides novel evidence suggesting that invasive and native communities have different biomass – body mass scaling patterns, which likely depend on differences in their trophic ecology and body size distributions. Our results suggest that restoration efforts using environmental flows and common carp control has potential to boost native fish biomass to more than double the current level. [ABSTRACT FROM AUTHOR]

Lake sturgeon (Acipenser fulvescens) were once abundantly distributed throughout the Laurentian Great Lakes. However, widespread overharvesting and habitat degradation has diminished their numbers. The lower Niagara River contains one of the few remnant lake sturgeon populations in New York State. This study determined the diet of adult lake sturgeon and quantified their trophic position in a food web dominated by non-native species. Stomach content analysis assessed recent diet, and stable isotope analysis (δ15N and δ13C) of blood and fin tissue quantified trophic position and carbon source over varying time scales. Two non-native species dominated the diet of lake sturgeon — the amphipod Echinogammarus ischnus (62% by number) and the round goby (Neogobius melanostomus) (44% by mass). Stable isotope analysis revealed that round goby was the primary contributor to the long-term (i.e., fin) average diet, whereas short-term (i.e., blood) diet was more diverse. In contrast with findings from other systems, we found that adult lake sturgeon in the lower Niagara River were primarily piscivorous, actively targeting live fish prey. The recovery of this population is potentially supported by the high availability of energetically rich but non-native food resources. [ABSTRACT FROM AUTHOR]

This study aimed to understand the use of “invasive species” as a normative concept and discuss its implications in conservation science, using introduced ascidians worldwide as model species. A specific search in Web of Science was performed and articles suitable for analysis were selected. Each article was classified according to the type of environment, species under study, type of effects and spread that ascidians are linked to. Most of the 184 articles analysed did not consider dispersal or effects as study subject (82 and 71%, respectively). Most research was conducted in laboratory conditions (41%) or human-made environments (32%) or indicating few escapes to natural environments. Almost half of the articles (47%) were made with the six more conspicuous introduced ascidians and this raised to 70% while considering articles that worked with two or more (pooled) species. The normative use of “invasive” is widely used regarding introduced ascidians. Spread and effects, necessary conditions to consider a species as invasive, are notoriously understudied. Most research was not conducted in natural environments and over a few species, weakening the perception of introduced ascidians as a conservation problem. To discuss the extent of the normative use of invasion science is important to distinguish two phenomena: are some species intrinsically problematic for conservation (i.e. invasive) or is the movement of non-native species (i.e. biological invasion) the conservation problem? By using invasive as a normative concept, we risk ending with a weakened concept potentially hindering the progress of invasion science. [ABSTRACT FROM AUTHOR]

Invasive marine species (IMS) are thought to be one of the most serious anthropogenic threats to global marine biodiversity. There are numerous reports of IMS being introduced into new areas throughout the world, but relatively few are in tropical locations. It has been suggested that this is an artefact of our lack of knowledge species present in the megadiverse tropics and a lack of IMS surveys. The Pilbara in northern Western Australia (WA) is used as a case study to examine these questions. The area is at high risk of IMS because of extensive international shipping. A detailed literature search of marine biodiversity studies developed a database of 5,532 species recorded in the Pilbara. There have been numerous surveys for species on the Australian national and WA IMS lists but only one, the ascidian Didemnum perlucidum Monniot, 1983, has been found. [ABSTRACT FROM AUTHOR]

This work presents a current (2018) annotated list of marine NIS and cryptogenic species in Greek marine waters. For this purpose, we updated information from previous lists, included new data from several new NIS and cryptogenic records and recent taxonomic studies, and followed current taxonomic modifications for the alien/cryptogenic status of several introduced species. Our extensive literature survey and revisions resulted in the exclusion of 61 species, which were included in previous lists, and the addition of 41 new alien species reported in the 2016-2018 period plus ten old NIS records. The current number of introduced species in Greek waters whose presence is not questionable includes 214 alien species and 62 cryptogenic species. Approximately 80% of the introduced species in Greek Seas consists of the taxa--in decreasing order--Mollusca, Polychaeta, Crustacea, Fishes, and Macroalgae. Nevertheless, a considerable increase in the number of NIS Bryozoa and Ascidiacea was observed within the last decade. Unaided natural dispersal of Lessepsian immigrants (57%) and transport-stowaways (36.7%) are the major pathways of introduction reported for Greek waters. However, with few exceptions (6.8% of species), the confidence level in assigning a pathway was medium to low. Several species reported from adjacent marine areas are expected to reach Greek waters within the next years. The intensification of underwater observations by citizen scientists combined with further research in hot spot areas, understudied habitats and overlooked taxa will significantly raise the number of NIS species in Greek waters. This study can serve as a basis that could greatly benefit from the coordination and harmonization of monitoring initiatives under international, EU and Regional Policies, and the compilation of new data from established monitoring programs, and rapid assessment surveys. [ABSTRACT FROM AUTHOR]

International and national guidelines and regulations to limit the inadvertent transfer of non-native species on the submerged surfaces of vessels and mobile infrastructure are progressing. However, methods to assess compliance must be developed to assist both regulators and industry. While there is a history of biofouling inspections in maritime industries, including commercial shipping and infrastructure, such surveys are tailored for vessel safety and performance rather than being driven by biosecurity purposes. Thus, these inspections are likely inadequate for confirming compliance with biosecurity regulations. To determine regulatory compliance, agencies will likely rely on a combination of risk profiling, assessment of documentation of biofouling management, archival data and images, and real-time in-water surveys made by divers or remotely operated vehicles (ROVs) specific to biosecurity regulations. Divers may exceed ROVs at finding organisms in recesses and other topographically complex areas, and when regulations require confirmation of species identity or viability. In contrast, ROVs may be well suited for regulations that establish upper thresholds on biofouling levels with little concern for organism identity or condition. Several factors will inform how a survey is conducted, including cost, the type of data required by regulations, environmental conditions, safety, and logistics. Survey designs and requirements should be transparent to manage industry's expectations of border procedures, to increase the efficiency with which industry and agencies manage biofouling and potentially align the evaluation of best practices in hull and niche area maintenance across jurisdictions. [ABSTRACT FROM AUTHOR]

The advent of container vessel networks has revolutionized global freight transport. While numerous studies in various disciplines such as economics, law, geography, engineering, and more, have discussed the impact of the "Container Revolution", we would like to share our insights here regarding the impact of container shipping networks on current and potential future trends in marine bioinvasion. We discuss the shift in centers and routes of high shipping intensity, and the importance of "Hub" versus "Feeder" ports, in relation to potential invasion routes. The increasing use of Ultra-Large Container Vessels (ULCV) worldwide is leading to further change in introduction dynamics: fewer vessels are now required for the transshipment of goods, as evident from our analysis of vessel movement via the Suez Canal. An investigation of adapted maintenance regulations is thus required in order to prevent the spread of alien species as fouling communities on particular niche areas of ULCVs. ULCVs further advance the hub-and-spoke network. Hub ports are characterized by the close physical proximity of large vessels (intercontinental mainliners) to many smaller vessels (feeders), calling in at local ports, as well as to other large vessels. This vessel interface occurs on a regular repetitive weekly cycle within a relatively small maritime environment. Thus a systematic network of potential vectors of bio-invasion is being established on both regional and continental levels. The increasing development of large container ports globally, and of larger vessels, demands a thorough investigation of their effect on bioinvasion potential. An integrated study of both the commercial and the biological networks is thus essential in order to fully comprehend their interaction. [ABSTRACT FROM AUTHOR]

The kelp Undaria pinnatifida, native to East Asian shores, was unintentionally introduced with Pacific oysters into the Mediterranean in 1971. Intentional introduction from there to the French Atlantic coast 12 years later led to a gradual spread to the British Isles and the North Sea. Here, we report on the northernmost established population in continental Europe, and suggest a further spread into Scandinavian waters to be almost inevitable. In 2016, several thalli were found washed ashore at the eastern side of the island of Sylt in the northern Wadden Sea (German Bight, Eastern North Sea). Most specimens bore fertile sporophylls and thallus lengths of >1 m were common. In June 2017, 91 sporophytes were found attached to a mixed bed of Pacific oysters and native blue mussels, located just below low tide level in a moderately sheltered position. Mean thallus length was 0.2 m and the longest 0.7 m. Most had distinctive sporophylls and released spores in the laboratory. From sporophylls collected in the previous year, we successfully reared a new generation, demonstrating the kelp's potential for further spread by natural means or human vectors. [ABSTRACT FROM AUTHOR]

The invasive Asian shore crab, Hemigrapsus sanguineus, is ubiquitous in the rocky intertidal zone of the western North Atlantic. A likely contributor to this colonization is that H. sanguineus is able to handle a wide range of salinities, and is thus more likely to spread through a greater geographic area of estuaries. This study investigated the salinity effects on this animal by observing survival across a range of salinities, the maintenance of hemolymph osmolality under different salinities, and behavioral preference for and avoidance of salinities. H. sanguineus showed high survival across a broad range of salinities, had little change in hemolymph osmolality over a short-term salinity shock, and behaviorally distinguished between salinities when presented with a choice, under both acclimation salinities of 5 PSU or 35 PSU. Such results suggest H. sanguineus has a hardiness for the rapid changes in salinity that happen in the intertidal zone, yet is capable of physically moving to a more optimal salinity. This enhances their competitiveness as an invader, particularly surviving lower salinities that present challenges during high-precipitation events in rocky intertidal areas, and partially explains this species' dominance in this habitat type. [ABSTRACT FROM AUTHOR]

Abstract: Propagule pressure plays a key role in the successful establishment of introduced species. Explaining invasion patterns, predicting future invasions and reducing invasion rates are priority areas of research and management, especially in marine systems, which need more detailed correlates and invasion predictors. The commercial maritime shipping fleet is the most prolific long distance anthropogenic transfer mechanism (vector) of marine non‐indigenous species on a global scale, causing invasions of coasts by a wide diversity of organisms. Although most vessel arrivals provide an opportunity for organism introductions, there are often substantial differences among ship types—in both their “morphological traits” (structural design) and “behavioural ecology” (cargo delivery model and operational tempo)—that influence propagule delivery by ballast water and biofouling, the two dominant sources or sub‐vectors for ship‐mediated species transfers. We reviewed ship specialization and its implications for marine invasion and vector management. First, we identified factors that affect ship‐mediated propagule delivery characteristics (number, identity, diversity and quality/condition), classifying these as ship type independent or dependent factors. Second, we compared the relevance of these factors for both ballast water and biofouling. Third, we estimated and compared the magnitude of several key factors affecting propagule delivery among seven major ship types. Typical voyage speed varies by 74% and port residence time varies sixfold among ship types. Similarly, typical ballast water discharge varies by an order of magnitude among ship types. These and other ship type dependent factors affect propagule delivery characteristics, resulting in uneven magnitude of species transfer among ship types. Policy implications. Variation among commercial ship types is rarely integrated into analyses of marine bioinvasions and proxy measures of propagule delivery. Their inclusion may lead to more robust explanation, prediction and management of marine invasions. Risk analyses that account for differences among ship types and prevailing traffic directionality will likely offer greater insight than null models, which treat ships equally. Furthermore, ballast treatment technologies and hull husbandry may advance to reduce species transfers more effectively when tailored for different ship types, recognizing the variation and operational constraints (that affect propagule delivery) among the diverse range of ship types. [ABSTRACT FROM AUTHOR]

Aim: Invasive species are of increasing global concern. Nevertheless, the mechanisms driving further distribution after the initial establishment of non-native species remain largely unresolved, especially in marine systems. Ocean currents can be a major driver governing range occupancy, but this has not been accounted for in most invasion ecology studies so far. We investigate how well initial establishment areas are interconnected to later occupancy regions to test for the potential role of ocean currents driving secondary spread dynamics in order to infer invasion corridors and the source-sink dynamics of a non-native holoplanktonic biological probe species on a continental scale. Location: Western Eurasia. Time period: 1980s-2016. Major taxa studied: 'Comb jelly' Mnemiopsis leidyi. Methods: Based on 12,400 geo-referenced occurrence data, we reconstruct the invasion history of M. leidyi in western Eurasia. We model ocean currents and calculate their stability to match the temporal and spatial spread dynamics with large-scale connectivity patterns via ocean currents. Additionally, genetic markers are used to test the predicted connectivity between subpopulations. Results: Ocean currents can explain secondary spread dynamics, matching observed range expansions and the timing of first occurrence of our holoplanktonic non-native biological probe species, leading to invasion corridors in western Eurasia. In northern Europe, regional extinctions after cold winters were followed by rapid recolonizations at a speed of up to 2,000 km per season. Source areas hosting year-round populations in highly interconnected regions can re-seed genotypes over large distances after local extinctions. Main conclusions: Although the release of ballast water from container ships may contribute to the dispersal of non-native species, our results highlight the importance of ocean currents driving secondary spread dynamics. Highly interconnected areas hosting invasive species are crucial for secondary spread dynamics on a continental scale. Invasion risk assessments should consider large-scale connectivity patterns and the potential source regions of non-native marine species. [ABSTRACT FROM AUTHOR]

Nearly 300 coastal marine species collected from > 630 debris items from the 2011 Great East Japan earthquake and tsunami have landed alive along the North American Pacific coast and the Hawaiian Archipelago. We synthesized life history, environmental, and distributional traits for 103 of these species and compared species with ( n = 30) and without ( n = 62) known invasion histories. The species represent 12 phyla, and Mollusca, Crustacea, and Bryozoa accounted for 71 of the 103 species. The majority are native to the Northwest Pacific and the Central Indo-Pacific. Species with known invasion history were more common on artificial and hardpan substrates, in temperate reef, fouling, and flotsam habitats, at subtropical and tropical temperatures, and exhibited greater salinity tolerance than species with no prior invasion history. Thirty-five Japanese tsunami marine species without prior invasion history overlapped in ordination trait space with known invaders, indicating a subset of species in this novel assemblage that possess traits similar to species with known invasion history. [ABSTRACT FROM AUTHOR]

Marine debris from the Great Tsunami of 2011 represents a unique transport vector for Japanese species to reach Pacific North America and Hawaii. Here we characterize the invasion risk of invertebrate species associated with tsunami debris using a screening-level risk assessment tool – the Canadian Marine Invasive Screening Tool (CMIST). Higher-risk invertebrate invaders were identified for each of five different ecoregions. Some of these are well-known global invaders, such as the mussel Mytilus galloprovincialis and the ascidian Didemnum vexillum which already have invasion histories in some of the assessed ecoregions, while others like the sea star Asterias amurensis and the shore crab Hemigrapsus sanguineus have yet to invade large portions of the assessed ecoregions but also are recognized global invaders. In general, the probability of invasion was lower for the Gulf of Alaska and Hawaii, in part due to lower climate matches and the availability of other invasion vectors. [ABSTRACT FROM AUTHOR]

Predatory crabs are considered amongst the most successful marine invasive groups. Nonetheless, most studies of these taxa have been descriptive in nature, biased towards specific species or regions and have seldom considered traits associated with invasiveness. To address this gap in knowledge, this study presents a global review of invasions by this group and applies biological trait analysis to investigate traits associated with invasion success. A total of 56 species belonging to 15 families were identified as having spread outside their native ranges. The family Portunidae supported the highest number of alien species (22). Most crabs had their origin in the North West Pacific IUCN bioregion while the Mediterranean Sea received the most species. No traits associated with successful establishment were identified, but this finding may reflect the paucity of basic biological knowledge held for many species. This lack of foundational knowledge was unexpected as crabs are large and conspicuous and likely to be well studied when compared to many other groups. Addressing this knowledge gap will be the first step towards enabling approaches like biological trait analysis that offer a means to investigate generalities in invasions. [ABSTRACT FROM AUTHOR]