The presence of the North American Marmorkrebs (Procambarus fallax f. virginalis) in European inland waters is entirely driven by ongoing propagule pressure from the ornamental trade. Since 2003 at least 25 independent introduction events have been confirmed, of which some have eventually resulted in established populations. This study links a maximum-entropy model that forecasts the probability of Marmorkrebs introduction based on socio-economic predictors to an updated species distribution model based on environmental predictors in order to explore the risk of further Marmorkrebs establishment in Europe. In line with related research, the probability of Marmorkrebs release was largely affected by gross domestic product and human population density, i.e. predictors very likely related to the density of Marmorkrebs owners, whereas environmental suitability was mostly influenced by minimum temperature and the availability of lentic habitats, which was indirectly assessed by terrain slope. While considerable parts of Europe were predicted as potentially suitable for establishment, high probabilities of introduction were forecasted in much smaller geographic areas. The consensus map of the model predictions suggests that introduction and subsequent establishment of Marmorkrebs is likely to occur in much of Germany, the Benelux countries, England, Italy, and areas of high human population density throughout France and Spain, as well as parts of southernmost Scandinavia and Southeastern Europe. Monitoring trades of Marmorkrebs in these high-risk regions is recommended and implications for proactive measures are discussed, including the need for consistent trade regulations at the EU level.

The commercial bait trade is one pathway for aquatic invasive species (AIS) introductions, as non-target bait species can be accidentally sold to anglers who either inadvertently or intentionally release them while fishing or as excess bait. Prevention of AIS introductions via the bait trade requires a two-tiered management approach, which includes both regulation of the bait industry and angler education. Retail bait shops may offer opportunities for public education regarding AIS, however it is unknown how often shops are targeted for such purposes and how viable this method of angler education is on a temporal scale. The goals of this research were to 1) quantify the current distribution of AIS signage in retail bait shops in the Great Lakes region and 2) estimate the long term viability of using retail bait shops as platform for angler education. Additionally, we present an up-to-date summary of bait industry regulations across the Great Lakes jurisdictions. Of the 525 bait shops visited in 2012 and 2013, 22% displayed some form of AIS educational materials or signage. Additional signs were distributed during initial visits and, during revisits after one calendar year, 54% of shops still displayed the provided signage. The presented summary of bait regulations for Great Lakes jurisdictions indicates multiple discrepancies across the region, which may hinder successful management strategies. Future management goals should consider additional methods of angler education and coordinating regulations across the Great Lakes to improve upon AIS prevention.

Alligator weed Alternanthera philoxeroides (Mart.) Griseb. is an amphibious plant that aggressively invades aquatic and terrestrial environments. It has invaded at least 14 countries and is difficult to control. The present study investigates the effectiveness of herbicides and physical removal in eliminating patches of aquatic alligator weed in an early stage of invasion. This paper firstly describes a screening trial to determine the relative efficacy of single application of three herbicides used in Australia (glyphosate, metsulfuron-methyl ± surfactant, and dichlobenil), each applied at three rates to containers of alligator weed. Control was greatest for all herbicides at rates higher than the manufacturer’s recommendation (label rate). Glyphosate at 3 × label rate (3.6 kg a.i. ha-1; 10.8 g a.i. L­1) and dichlobenil at 2 × label rate (31 kg a.i. ha-1) provided the greatest level of control at 48 and 91 weeks after treatment. The presence of surfactant did not improve metsulfuron-methyl efficacy. Field studies were then carried out to evaluate the effectiveness of repeated physical removal and repeated applications of chosen herbicides to eliminate patches of aquatic alligator weed in an early stage of invasion of two urban streams in Melbourne, Australia. Glyphosate and metsulfuron-methyl (without a surfactant) were applied to patches of aquatic alligator weed in a best practice regime, consisting of up to three applications per year for up to five consecutive years. Glyphosate was applied at 3 × label rate, as well as at label rate. No alligator weed remained after two years of the herbicide application regime for patches treated with metsulfuron-methyl, while for glyphosate alligator weed remained in only one of 18 patches after three years. Physical removal eliminated 75% of patches after initial treatment and minimal follow up treatments were required where regrowth occurred. This study demonstrates that the management methods utilised are capable of eliminating patches of aquatic alligator weed in an early stage of invasion in two to three years.

The red swamp crayfish (Procambarus clarkii) has been widely introduced into aquatic systems all around the world, triggering multiple impacts. In Doñana Natural Area, Abalario and the Biological Reserve of Doñana, Spain (one of the most important biodiversity reserves in Europe), the red swamp crayfish was first introduced in 1974 and expanded its range quickly through marsh habitat, but distributed more slowly throughout scrubland ponds. Water persistence, salinity, and substrate can condition the presence of the species in the wild. Before the creation of the Natural Area and the Biological Reserve of Doñana, farmers dug artificial water points in some scrubland ponds to provide water throughout the year for livestock. Once declared a protected area, managers assumed control of the maintenance of the park and opened new water points as a wildlife management tool. The aim of the study presented here was to determine the environmental conditions that favor the spread of crayfish in the temporal ponds of Doñana and whether the occurrence of water points increases the spread of crayfish. For this purpose, we sampled crayfish using a sweep net in 60 randomly selected ponds in two different areas of Doñana. Crayfish occurrence was significantly related to the presence of seasonal streams connecting the ponds with refuge areas and to the presence of artificial water points within the pond. The probability of occurrence of red swamp crayfish in a pond without seasonal streams was more than 5 times lower than that in a pond with seasonal streams. The probability of crayfish occurrence in ponds without artificial water points was 2.5 times lower than that in ponds with artificial water points. We review the advantages and disadvantages of water points as a management tool.

Management of non-native fish species is informed by monitoring their temporal and spatial distribution. There are few published analyses of temporal patterns of established non-native fish species. The objective of this study was to examine the utility of the American Fisheries Society’s (AFS) lists of fish names for quantifying trends in the number of established non-native fishes as a first step in determining trends in the number of invasive fish species in the continental United States. As of the 2013 AFS list, there were 66 non-native species listed as established in the continental U.S., a 2.5-fold linear increase from 1970. All of the species, except two, established before 2013 persisted in 2013. The number of species added to each subsequent list increased throughout the period. Eight species were added from 1970 to 1980, 14 from 1980 to 1991, 18 from 1991 to 2004, and 5 from 2004 to 2013. The number of listed non-native families increased linearly from 8 to 19 during the same period. Cichlids, cyprinids, and poeciliids were the most represented families (about 73% of the established species listed in 1970, 1980, and 1991, and about 56% on the 2004 and 2013 lists). Converting the trend in the number of non-native species into the number of invasive species is difficult because of lack of available impact information and the dependency on human perception and value.

The silver-cheeked toadfish Lagocephalus sceleratus is one of the most recent invaders in the Mediterranean Sea and a serious risk for public health. In June 2011, an awareness campaign to disseminate information related with this toxic species was launched by the Tunisian Ministry of Agriculture. Whilst providing a step toward the development of an appropriate early warning system, this case highlights a remarkable geographical extension of L. sceleratus along the entire Tunisian shoreline (from the island of Djerba to the region of Tabarka). We illustrate how the first step in the process of effectively managing the risks posed by an invasive species is to engage and communicate with the public.

Broad-scale niche models are good for examining the potential for invasive species occurrences, but can fall short in providing managers with site-specific locations for monitoring. Using Oklahoma as an example, where invasive bighead carp (Hypophthalmichthys nobilis) are established in certain reservoirs, but predicted to be widely distributed based on broad-scale niche models, we cast bighead carp reproductive ecology in a site-specific geospatial framework to determine their potential establishment in additional reservoirs. Because bighead carp require large, long free-flowing rivers with suitable hydrology for reproduction but can persist in reservoirs, we considered reservoir tributaries with mean annual daily discharge ≥8.5 cubic meters per second (m3/s) and quantified the length of their unimpeded portions. In contrast to published broad-scale niche models that identified nearly the entire state as susceptible to invasion, our site-specific models showed that few reservoirs in Oklahoma (N = 9) were suitable for bighead carp establishment. Moreover, this method was rapid and identified sites that could be prioritized for increased study or scrutiny. Our results highlight the importance of considering the environmental characteristics of individual sites, which is often the level at which management efforts are implemented when assessing susceptibility to invasion.

The Chinese mystery snail (Bellamya chinensis) is a freshwater snail native to Southeast Asia, Japan, and Russia and is currently classified as an invasive species in at least 27 states in the USA. The species tolerates a wide range of environmental conditions, making management of established populations difficult. We tested the efficacy of two traditional chemical treatments, rotenone and copper sulfate, on the elimination of adult Chinese mystery snails in laboratory experiments. All snails (N=50) survived 72-hour exposure to rotenone-treated lake water, and 96% (N=25) survived 72-hour exposure to pre-determined rotenone concentrations of 0.25, 2.5, and 25.0 mg/L. All snails (N=10) survived exposure to 1.25 mg/L copper sulfate solution, 90% (N=10) survived exposure to 2.50 mg/L copper sulfate solution, and 80% (N=5) survived exposure to 5.0 mg/L copper sulfate solution. Neither rotenone nor copper sulfate effectively killed adult Chinese mystery snails in laboratory experiments, most likely due to their relatively large size, thick shell, and operculum. Therefore, it appears that populations will be very difficult to control once established, and management should focus on preventing additional spread or introductions of this species.

Chromolaena odorata (L.) King and Robinson (Asteraceae: Eupatorieae) is an invasive perennial weedy scrambling shrub of neotropical origin, widely acknowledged as a major economic and ecological burden to many tropical and subtropical regions of the world including Nigeria. Here, we examine the invasion and management of C. odorata in Nigeria over the last seven decades using historical records and field surveys and ask: (i) Does the usefulness of C. odorata influence its invasion success? (ii) Is a coordinated control approach against C. odorata needed in the face of its usefulness or do we need to develop strategies for its adaptive management? We searched major institutional libraries in Nigeria and carried out extensive research of historical records using different data base platforms, including Google Scholar, Science Direct, ISI web of Science, SciFinders and Scopus. Apart from the biological invasive characteristics of C. odorata and the increased anthropogenic disturbances occurring over the time period, the records indicate that the ethno-pharmacological, funcigicidal, nematicidal importance of the plant and its use as a fallow species and as a soil fertility improvement plant in the slash and burn rotation system of agriculture is partly responsible for the invasion success of the weed. The current distribution and infestation levels of this invasive weed in Nigeria are mapped. The current methods of control and the failed attempt made by the Nigerian government to eradicate the weed between the late 1960s and 1970s are discussed. We argue that even in the face of the usefulness of C. odorata, it is reasonable to implement a nationwide coordinated control programme against it with biological control as a core component, because weed biological control does not eliminate the target species, instead it aims to establish an equilibrium which maintains the weed’s population below the level where it causes significant harm to natural and semi-natural ecosystems.

Rigorous evaluation of ballast water management systems (BMWSs) at land-based test facilities requires that water used in testing meets minimum concentrations of dissolved and particulate material, for example, using the criteria in the U.S Environmental Technology Verification (ETV) Program’s protocol for testing of BWMSs. Here, uptake water (“challenge water”) can be augmented with compounds to meet these benchmarks. In this study, we evaluated materials used to supplement dissolved organic matter (DOM), particulate organic matter (POM), and mineral matter (MM) used to achieve challenge water criteria. To determine the additives’ contributions to DOM and POM pools, the mass yields of Camellia sinesis (decaffeinated iced tea) extract and humic matter were calculated at different temperature and salinities. Additionally, the response of ambient organisms to these additives was measured in mesocosm experiments, in which changes in organism concentrations were measured after a 5-d holding time. Living organisms were grouped into three size classes: ≥50 µm (nominally zooplankton), ≥10 to <50 µm (nominally protists), and <10 µm (measured as culturable, aerobic, heterotrophic bacteria). Significant differences in concentrations between control and treatment mesocosms after 5 d were not detected for organisms in the ≥10 to <50 µm or the ≥50 µm size classes. However, bacterial concentrations increased significantly in mesocosms augmented with exogenous materials. Thus, direct impacts (or indirect impacts through increased bacterial concentrations) were not apparent among organisms in the two largest size classes. Finally, a literature review of DOM, POM, and total suspended solids concentrations in coastal waters was conducted. It revealed that the challenge water concentrations outlined in the ETV protocol are at the middle to upper range of concentrations observed in coastal and estuarine water. The mean DOM and POM concentrations in this data set typically fell short of the ETV minimum requirements, and more data are needed to fully assess the suitability of these requirements.

The invasive Asian clam Corbicula fluminea (Müller, 1774) has established a high density and self-sustaining population within the tidal reaches of the River Barrow, Ireland. A field trial was carried out to test the respective efficacy of three different mechanical dredge methods at reducing Corbicula clam numbers by estimating changes in abundance and biomass immediately following dredging. Quadrat samples were collected by SCUBA divers before and after dredging. A maximum pre-dredge density of 17,872 individuals/m2 and a biomass of 43.94 kg/m2 was recorded. Three sites which supported different population density and biomass levels within the tidal section of the River Barrow were subject to each of the dredge methods. A reduction of greater than 95% biomass and 95% density was achieved at the high density, high biomass site, while an 82% biomass and 65% density reduction was recorded at the low density, low biomass site. A 74% biomass and 92% density reduction was achieved at the high density, low biomass site. The methodology and results indicate that, while dredging can achieve a large reduction in Corbicula population numbers, further research is required before this can be considered as a management tool for control of Asian clams.