The European Commission has recently adopted its EU Biodiversity Strategy for 2030, which sets out an ambitious plan for reversing biodiversity loss, and preserving and restoring protected ecosystems. A central binding target is focused on enlarging the EU network of legally protected areas (Natura 2000, the largest global network of the world), and on maintaining or improving the conservation status of all vulnerable habitats and species included in them. Biological invasions are currently a major threat to Natura 2000, so fulfilling the objectives of the EU Biodiversity Strategy calls for stepping up the implementation and enforcement of the relevant legislation on the matter, which has been thoroughly revised over the last decade. We discuss here the regulatory aspects of legislation on invasive alien species (IAS) that need to be optimised to address the challenge posed by biological invasions to the Natura 2000 network in the light of the new EU Biodiversity Strategy. We highlight that, while the EU has designed a solid regulatory framework to tackle the threat of biological invasions, its successful implementation will mainly rely upon appropriate national enforcement and allocation of economic and human resources. Despite previous warnings, the creation of dedicated EU funding mechanisms to support a comprehensive implementation of the legislation still remains a priority. Due to the yet small number of IAS regulated at the EU level, prevention and management of IAS will largely depend on national and local administration efforts, and on regional coordination and cooperation across neighbouring countries. Therefore, a well-integrated system responsible for biosecurity, pests and invasive alien organisms at the EU level would be better accomplished through a centralized, independent EU agency of new creation. Likewise, the establishment of a similar lead agency at the MS level, with special focus on IAS management in Natura 2000, is recommended to navigate the existing complex regulatory framework.

A major historical challenge for the management of anthropogenic introductions of species has been the absence of a globally standardised system for species nomenclature. For over a decade, the World Register of Marine Species (WoRMS) has provided a taxonomically authoritative classification and designation of the currently accepted names for all known marine species. However, WoRMS mainly focuses on taxonomy and does not specifically address species introductions. Here, we introduce the World Register of Introduced Marine Species (WRiMS), a database directly linked to WoRMS that includes all introduced marine species, distinguishing native and introduced geographic ranges. Both the WoRMS and WRiMS contents are continually updated by specialists who add citations of original species descriptions, key taxonomic literature, images and notes on native and introduced geographic distributions. WRiMS editors take responsibility for assessing the validity of species records by critically evaluating if a species has been introduced to a region, erroneously identified and/or potentially naturally present in a region but previously unnoticed. WRiMS currently contains 2,714 introduced species. The amount and quality of the information entered depend on the availability of experts to update its contents. Because WRiMS is global and it combines species taxonomic and geographic information with links to other resources and expertise, it is currently the most comprehensive standardised database of marine introduced species. In addition, WRiMS forms the basis for a future global early warning system of marine species introductions.

Since the January 2007 discovery of quagga mussels (Dreissena rostriformis bugensis) at Lake Mead National Recreation Area, the National Park Service has worked with numerous agencies and partners to prevent further spread of invasive species through inspection and decontamination of recreational vessels and boater education programs. We applied geographic and demographic analysis techniques to data collected at inspection and decontamination stations within the park and data from inspection stations across the western United States to better understand the visitor boating population. Using ArcGIS ESRI Tapestry software and the home zip codes of recreational boaters whose vessels were inspected within the park, we classified local and non-local boaters into demographic groups with the goal of developing more targeted educational programs. Demographic results indicate distinctive trends within the boating population including: higher median incomes, high levels of education, and boat owner median ages in the mid-30s. Economic and behavioral patterns of Lake Mead boater demographics combined with a synthesis of available research on behavior change in environmental campaign design demonstrate the need for targeted outreach to increase the effectiveness of aquatic invasive species (AIS) programs and further reduce AIS transmission risk.

Improving the knowledge on the distribution and impacts of alien species in poorly studied regions is essential to raise national awareness as well as support effective management policies. Here we present a systematic review of the current state of knowledge regarding biological invasions in Mexico, providing a list of alien plant and animal species that can be considered either alien or invasive. Our search in scientific literature comprised a total of 2664 alien species recorded in Mexico, where approximately 36.2% of alien species were considered invasive, a much higher figure than previous estimates. Most alien species were introduced from the Europe, Asia, and Africa, primarily for ornamental use, food, or livestock fodder. The current data demonstrate that alien and invasive species continue to enter and spread within Mexico, and it also emphasizes the necessity and responsibility to develop scientific strategies to minimize the impact of biological invasions and to raise public awareness of the problem. This review will help fill some gaps in the knowledge about biological invasions in Mexico, where the list of species can serve as a scientific basis for future studies.

The pet trade is known to be one of the main sources of invasive species including freshwater crayfish, which cause socio-economic losses and negative impacts on native biota in many regions where introduced. Indonesia was identified as the leading supplier of ornamental crayfish globally but the local market has been neglected even though certain non-native species were reported previously. Based on the survey of pathways and culture of ornamental crayfish in Java, six non-native species were recorded: Cherax destructor, C. quadricarinatus, C. peknyi, C. snowden, C. warsamsonicus, and P. clarkii. The latter species originates from North America and serves as a vector of crayfish plague, i.e. a disease lethal for non-North American crayfish species. Crayfish are cultured both in outdoor and indoor facilities as well as in natural lakes and reservoirs. Harvested crayfish are transported via numerous routes across most of the island of Java. It is obvious that the local market for ornamental crayfish is well-developed and Jakarta, Surabaya and Yogyakarta were identified as hotspots of this trade. Further monitoring, detailed analysis of the market and a ban of high-risk P. clarkii are recommended to improve management and existing legislation.

A small number of longhorn beetle species (Coleoptera: Chrysomeloidea: Cerambycidae) have the potential to become invasive forest pests. International trade in live plants and wood packaging material are known invasion pathways for longhorn beetles. Once an invasive pest is intercepted in a new region, a rapid pest risk analysis is often needed to determine the appropriate response. For accurate risk quantification, natural history evidence is necessary. This information is also vital in preventing introduction. This study gathered insect collection data, especially references to host plants, of xylophagous longhorn beetles from the Institute of Zoology, Chinese Academy of Sciences, Beijing, China. Beetle associations with three important host groups were investigated: Fagaceae, Citrus spp., and avocado (Persea americana). We performed a systematic literature review to identify previously documented cerambycidae associated with these plants. Here, we report insect-plant host associations for 39 species of longhorn beetles based on a review of the literature; 43 interactions were documented, 10 interactions were novel. No host associations were recorded with avocado in China. This information serves as a foundation for pest risk analysis in determining threats posed by potentially invasive longhorn beetles into new regions.

Alien goldenrods (Solidago and Euthamia) invade improperly managed grasslands causing serious environmental problems. The general knowledge regarding habitat resistance against invasion does not allow predicting whether species-rich semi-natural meadows or highly productive artificially sown grasslands are more resistant to invasion by goldenrods. To test the differences in resistance, an experiment was conducted. A community resembling a semi-natural, species-rich meadow and a commercial grassland was created in containers in 2018 using seed mixes, with open soil serving as the control. Three goldenrod seedlings representing particular species (Solidago canadensis L. s.l., S. gigantea Aiton, and Euthamia graminifolia (L.) Nutt.) were planted in the test containers with the different communites in 2019. The vegetation was cut once per year during the first and second years of the experiment. In September of the third year, the number of goldenrod ramets, the height of the tallest goldenrod ramet, and the flowering stage were measured and assessed. In addition, the dry biomass of goldenrods and accompanying species were weighed. The results showed no significant differences between total biomass production of the examined communities, except for E. graminifolia, for which species-rich meadow produced more biomass than the commercial grassland and control. Both communities strongly reduced ramet numbers and height and goldenrod biomass production compared to the control. No differences were found between these two vegetation types, except for the flowering stage of S. canadensis and E. graminifolia, which could not produce seeds in the species-rich meadow community. The results suggest that semi-natural, species-rich meadows are reasonable alternatives to species-poor commercial grasslands to control goldenrod invasion.

Gummosis on Acacia decurrens, an invasive tree species that was established in Merapi Volcano National Park (MVNP) after the eruption of the Mount Merapi volcano in 2010, was studied to i) identify the causal organism of the disease, ii) analyze the disease symptoms, iii) understand the spatio-temporal distribution of gummosis in the tree population and iv) examine how the disease affects the anatomy of tree wood. Pathological, morphological and molecular assessments were used in this study. Ceratocystis fimbriata was found associated with gummosis in the affected trees. The disease spread was probably aided by an ambrosia beetle, Euwallacea sp., which bores holes in the stem. The number of parenchyma cells in infected stems was significantly higher than in healthy stems, which apparently facilitated water and nutrition transport within trees, helping them to grow normally despite serious gummosis. The disease is noted to spread from the base of the trees, where the ambrosia beetle bores holes first, to the upper part. The management of invasion by A. decurrens in the MVNP area poses a serious challenge due its success as an invader in the volcano-impacted area and the threat of the gummosis pathogen spreading to other species, both of which will affect the regeneration and establishment of native species and recovery of the ecosystem.

Detection of invasive species and decisions centered around early detection and rapid response (EDRR) are notorious challenges for decision makers. Detection probability is low for cryptic species, resources are limited, and ecological harm (especially for island ecosystems) can result from failure to remove invasive species due to inadequate or delayed surveillance efforts. Due to the proximity to the U.S. territory of Guam and inter-island traffic, the Commonwealth of the Northern Mariana Islands (CNMI) is at high risk of colonization by the invasive and cryptic brown treesnake (Boiga irregularis; BTS). There have been numerous reports of snakes and 7 confirmed specimens secured at ports of entry on the island of Saipan in the CNMI over the last four decades, raising the possibility that a population might be established. Establishment of BTS on Saipan is a major concern, as evidenced by the ecological and economic disruption that occurred on Guam. We evaluated the possibility of a small localized population on Saipan using evidence from surveillance efforts in 1999, 2007, 2009, 2016, and 2018, and from results of expert assessment of the credibility of non-confirmed reports of snakes for the period 1982–2013. For active surveillance efforts, we use a Poisson-based model to estimate the 95% probability of at least one snake being detected at a stated density given the level of sampling effort and detection probability. Based on this collective evidence we conclude there is a low probability that Saipan currently has an incipient population of BTS. However, with the continued presence of BTS on Guam, continuing commercial and military transportation in the region, and relief shipments responding to increased storm intensity, Saipan remains highly vulnerable to accidental introductions. Effective surveillance remains a crucial element for detection of any species, but this may be particularly true for a cryptic snake that is difficult to control once established.

We determined the efficacy of carbon dioxide (CO₂) for preventing larval (veliger) settlement of the invasive zebra mussel (Dreissena polymorpha) and compared the response of native juvenile mussels and macroinvertebrate and periphyton communities to hypercapnia. A microcosm system of control (ambient C_amb) and CO₂ treatments [low partial pressure of carbon dioxide, PCO₂ (C_low) = 35,094 µatm, and high PCO₂ (C_high) = 66,685 µatm)] was supplied with river water for 11 weeks. We measured zebra mussel settlement, juvenile native mussel (Lampsilis cardium and L. siliquoidea) growth and condition, and macroinvertebrate and periphyton community composition. Zebra mussels settled in all C_amb tanks (n = 4) from early July through August compared to one mussel in a CO₂ treatment tank over the same period. Native mussel growth, tissue condition, and shell condition were reduced in CO₂, particularly in the highest treatment. Benthic biomass (excluding zebra mussels) was similar in C_amb and C_low but was reduced in C_high. Macroinvertebrate community composition differed among treatments due to greater abundance of Chironomidae in C_low and Oligochaeata in C_high. Periphyton abundance and richness increased in both CO₂ treatments and was driven by increases in Cyanobacteria, Bacillariophyta, and Chlorophyta. Our results indicate that efficacious levels of CO₂ (~ 35,000 µatm PCO₂) for reducing biofouling by dreissenids are tolerable to most freshwater benthic taxa. Chronic elevated CO₂ infusion (> 35,000 µatm PCO₂) may reduce native mussel growth and condition and alter benthic invertebrate and periphyton community composition. Further refinement of CO₂ application strategies is needed to determine minimum effective dose and duration to prevent dreissenid settlement and minimize effects on nontarget organisms.

Invasive crayfish have adverse effects on habitats and native species. Control of invasive crayfish populations is a major challenge facing natural resource managers. This study evaluated the effectiveness and optimal conditions for the control agent carbon dioxide (CO₂), which can be diffused into water to facilitate capture of red swamp crayfish (Procambarus clarkii; RSC). The efficacy of CO₂ shows promise in its use for a variety of invasive aquatic species. Here, we evaluate CO₂’s ability to stimulate movements towards the shoreline and/or induce complete terrestrial emergence from outdoor ponds. Twelve pond trials were conducted using three, 0.02-ha experimental ponds at Auburn University, Alabama, USA. Silt fencing was installed on dry land around the perimeter of each pond with the lower 0.3 m of fencing accordion-folded to provide shelter and a collection point for emerging crayfish. Each pond was stocked with 100 RSC before testing. Experimental treatment ponds were then injected with gaseous CO₂ using porous air diffusers, whereas control ponds (C ponds) received no CO₂. Multiple water quality parameters were monitored hourly. Three independent treatment scenarios with CO₂ diffusion were crayfish captured at the end of trial only (F: final), crayfish captured hourly (H: hourly), and incorporation of continuous inflow of fresh water at a flow rate of 0.2 L/s into the central catch basin to serve as a refuge with crayfish captured hourly (R: refuge). In control ponds, crayfish were captured at the end of trial only. In F ponds, CO₂ diffusion for approximately five hours caused a mean of 12% of total crayfish to emerge from the water. However, capture efficiency was increased to a mean of 45% of total crayfish by increasing collection frequency to every hour and netting submerged crayfish near the water edge in addition to capturing terrestrially emerged crayfish. Presence of a freshwater inflow reduced capture efficiency in R ponds relative to H ponds. Odds of capturing crayfish increased with increasing water temperature, CO₂ concentration, crayfish mass, and with decreasing pH. Based on results, we provide a set of predictive equations as well as interactive calculators to help natural resource managers explore several environmental and treatment-related scenarios that predict changes in capture probability in small research ponds. Carbon dioxide shows promises as a tool to increase capture rate of RSC. It is not likely to be 100% effective by itself, but could be a useful component of an integrated management strategy.

High densities of invasive rusty crayfish on critical spawning reefs present a potential impediment to the recovery of native fish in the Laurentian Great Lakes. Suppression of rusty crayfish on spawning reefs to protect fall spawning native fishes in the Great Lakes is hampered by regular storm events and ambient weather conditions, limiting the number of practical days traps can be checked, cleared, and re-baited. The Gee minnow trap design is the most common gear for sampling and managing crayfish, yet design constraints of the standard Gee minnow trap manifest as tradeoffs between capture efficiency and retention for users. In this study, we compared catch rates from a semi-controlled field experiment and escapement probabilities from laboratory controlled trials for a Gee minnow trap, a modified Gee minnow trap with intention to reduce escapement, and an experimental flat-bottomed pyramid design which showed potential promise during prototype-stage development. Bayesian parameter estimation of generalized linear models applied to catch data suggested that standard Gee minnow traps performed at least as well and often better than both novel trap designs in catch rate and escapement probability. Escapement during laboratory controlled trials was high for all trap designs, demonstrating that retention of trapped individuals is a persistent problem for crayfish monitoring and management. We conclude from our data that standard Gee minnow traps are a sensible gear choice for monitoring and/or potential suppression efforts for invasive rusty crayfish on nearshore spawning reefs in the Great Lakes. However, modifications to its design to improve retention should yet be pursued.

The control of invasive species is of major importance for ecological conservation, and there is a need for more effective techniques and approaches to control these species, especially in open habitats. Two types of activities were conducted to control the population of largemouth bass (Micropterus salmoides) in Lake Izunuma-Uchinuma, Japan. The first activity was a lake wide catch using set nets deployed all along the lakeshore beginning in 2001. The second activity, beginning in 2004, focused on catches during the spawning season over spawning sites, distributed along lakeshore segments with sandy substrates. The efforts of both activities were similar (involving about 140 people/year). From 2001 to 2003, the catch per unit of fishing effort (CPUE) of largemouth bass using set nets increased; however, CPUE decreased dramatically after catches at the spawning sites started. The numbers of nests spawned, larvae, and adults of largemouth bass also decreased after the start of spawning site catches. In 2010, the CPUE of other fish species, whose numbers had decreased due to predation by largemouth bass, recovered to the same number as before the expansion of largemouth bass. Capturing largemouth bass at the spawning sites was an effective approach to controlling this species and conserving fish communities in the lake.

Biofouling of ship hulls is one of the most important vectors for the transfer of aquatic invasive species. These species cause widespread impacts to native environments and ecological communities, in addition to imposing financial costs for industry. Targeted surveillance and effective adaptive management require knowledge on the likelihood of new introductions of non-indigenous species (NIS). We develop a model of the likelihood of introduction and invasion of NIS for the port of Arzew (Algeria), based on the length of stay of vessels in the ports of call, the latitude of these ports, the geographical distance from the port of Arzew, ship’s speed, effectiveness of the antifouling system and antifouling strategy used in port of origin. We identified areas that represent a source of high risk species invasion, according to the environmental similarity of the ports of origin with the Arzew port using the Mahalanobis distance. We show that over one year, 738 trips have been made at the port of Arzew, inflicting a very high risk of invasion, in particular from six coastal ecoregions, (the Western Mediterranean ecoregion, the Northern and Central Red Sea, the South European Atlantic Shelf, the Ionian Sea ecoregion, the North Sea, and the Aegean Sea). These results can be used for invasive species management purposes, such as: the application of specific regulations to high-risk vessels and ports in order to minimize the transfer of these species. The methods and models developed here are transferable to any region around the world with similar data availability.