Introduced alien species bring potential adverse impacts on biodiversity and ecosystem functions. International shipping is an important vector for such unintentional introductions in aquatic environments. Therefore, in addition to climate change and eutrophication, increasing international shipping may enhance the spread of alien species into areas which have not previously been considered prone to alien invasions. One example of such development might be the recent invasion of the moss animal Pectinatella magnifica into Finnish inland waters, which are generally considered to be hostile to alien species. We took advantage of observations made by the general public and recorded by environmental authorities to describe the invasion history of the species in Finland. The records of P. magnifica were almost exclusively from the Vuoksi watercourse, where the species was most likely introduced by international shipping ca 10–15 years ago. The species occurred mainly in the vicinity of ports of international shipping, but was also abundant in an area with only domestic cargo transport. Only one confirmed observation in Lake Kirkkojärvi was from outside the Vuoksi watercourse. Most colonies were found attached to landing stages or submerged, relatively rigid water plants, and the species seemed to avoid less rigid water plants, such as water lilies. Once established, the species may spread by vectors such as recreational boating or water birds and fish. The species poses some risks to the ecosystem, including a risk to farmed and wild salmonid fish by serving as a potential host for the myxozoan endoparasite Tetracapsuloides bryosalmonae, the causative agent for proliferative kidney disease (PKD), known to be detrimental for salmonid fish.

Aquatic invasive species are an ongoing economic and ecological problem in Atlantic Canada. To optimize management efforts of high-risk species, we must quantify risk of invasion at scales relevant to management efforts. Here we provide an updated and improved detailed-level risk assessment (DLRA) for Didemnum vexillum that uses new methods and tools to quantify and discriminate risk of invasion to the region. The screening level risk assessment framework CMIST (Canadian Marine Invasive Screening Tool) was used in a novel context to calculate uncertainty-adjusted invasion risk scores for 13 assessment zones in Atlantic Canada. Assessments were informed by 1) environmental niche modelling (MaxENT) to predict areas suitable for establishment; 2) source-based vector analysis to quantify potential for arrival and spread of D. vexillum via high-risk vectors (i.e., commercial vessels, ferries, fishing vessels, and aquaculture transfers); and 3) updated ecological data from the literature. Overall invasion risk, likelihood of invasion, and impact of invasion were highest in Bay of Fundy assessment zones and lowest in the most northern zones (St. Lawrence estuary, northern Gulf and the east coast of Newfoundland). Connectivity with source zones of D. vexillum via both natural (e.g., currents) and anthropogenic vectors (e.g., vessels) is highest in the Bay of Fundy due to proximity to established populations and high levels of vessel traffic. Potential for impacts is highest where vulnerable populations (e.g., scallops) and highly or moderately suitable areas for establishment exist. These areas are in the Minas Basin, Chignecto Bay, southwest New Brunswick, and southwest Nova Scotia with smaller areas in Mahone Bay and offshore on Western Bank and Sable Island Bank. Projections of environmental suitability for 2075 show a northeastward shift, with areas of high suitability retained in the Bay of Fundy and expanding into the Northumberland Strait. To reduce further local spread in the Bay of Fundy, bottom-disturbing activities, such as dredging and trawling where D. vexillum is present, should be addressed. In addition, movement of vessels between source areas and areas of high environmental suitability should be monitored, especially in anomalously warm years when populations are likely to be larger. Targeted monitoring of areas of current and future environmental suitability with high connectivity to source zones of D. vexillum should also be considered to improve early detection of new populations.

Early detection is imperative for successful control or eradication of invasive species, but many organisms are difficult to detect at the low abundances characteristic of recently introduced populations. Environmental DNA (eDNA) has emerged as a promising invasive species surveillance tool for freshwaters, owing to its high sensitivity to detect aquatic species even when scarce. We report here a new eDNA assay for the globally invasive Asian clam Corbicula fluminea (Müller, 1774), with field validation in large lakes of western North America. We identified a candidate primer pair for the Cytochrome c oxidase subunit 1 (COI) gene for C. fluminea. We tested it for specificity via qPCR assay against genomic DNA of the target species C. fluminea, and synthetic DNA gBlocks for other non-target species within and outside of the genus Corbicula. Our best identified primer amplifies a 208-bp fragment for C. fluminea and several closely related species within the genus, but was specific for these non-native Asian clams relative to native mollusks of western North America. We further evaluated this assay in application to eDNA water samples for the detection of C. fluminea from four lakes in California and Nevada, United States, where the species is known to occur (including Lake Tahoe) relative to seven lakes where it has never been observed. Our assay successfully detected C. fluminea in all four lakes with historic records for this species, and did not detect C. fluminea from the seven lakes without known populations. Further, the distribution of eDNA detections within Lake Tahoe generally matched the known, restricted distribution of C. fluminea in this large lake. We conclude from this successful field validation that our eDNA assay for C. fluminea will be useful for researchers and managers seeking to detect new introductions and potentially monitor population trends of this major freshwater invader and other closely related members of its genus.

The European green crab, Carcinus maenas, has been established on the west coast of North America since at least 1989, yet populations were limited to coastal embayments for more than two decades. In 2012, the first population was identified within the Strait of Juan de Fuca, which provided the impetus to develop a citizen science program to monitor for invasive green crab within the inland marine waters of Washington State (USA). In 2016, 116 volunteers monitored 26 sites using baited traps and visual surveys. On August 30, 2016, a single live male crab (74 mm carapace width) was captured in Westcott Bay on San Juan Island, Washington, by volunteers – the first detected range expansion in these inland waters. In September 2016, an additional crab was collected in Padilla Bay, Washington. The citizen science program and subsequent rapid assessment efforts by multiple partners found one green crab molt carapace in Westcott Bay, and three additional live crabs in Padilla Bay. Based on our results, the current extent of the invasion might be spatially and numerically restricted, but the occurrence of green crab in the San Juan Islands and Padilla Bay could portend future establishment of the species in the inland waters of Washington State and elsewhere in the Salish Sea. The citizen science program and rapid assessment efforts serve the dual purpose of providing ongoing monitoring and limited control in habitats vulnerable to invasion.

Loricariid catfishes of the genus Pterygoplichthys are native to South America and have been introduced in many localities around the world. They are freshwater fishes, but may also use low-salinity habitats such as estuaries for feeding or dispersal. Here we report results of a field survey and salinity-tolerance experiments for a population of Pterygoplichthys sp. collected in Kerala, India. In both chronic and acute salinity-tolerance trials, fish were able to withstand salinities up to 12 ppt with no mortality; however, fish transferred to salinities > 12 ppt did not survive. The experimental results provide evidence that non-native Pterygoplichthys sp. are able to tolerate mesohaline conditions for extended periods, and can easily invade the brackish water ecosystems of the state. Further, Pterygoplichthys sp. from Kerala have greater salinity tolerance than other congeners. These data are vital to predicting the invasion of non-native fishes such as Pterygoplichthys spp. into coastal systems in Kerala and worldwide. This is particularly important as estuarine ecosystems are under threat of global climate change and sea-level rise. In light of the results of the present study and considering the reports of negative impacts of the species in invaded water bodies, management authorities may consider controlling populations and/or instituting awareness programmes to prevent the spread of this nuisance aquatic invasive species in Kerala.

A fast, accurate and simple method using liquid chromatography (LC) with UV detection was used for the on-site determination of the piscicide rotenone in water during fish control treatments. Sample volumes of 10 to 40 µL were loaded onto a Waters XBridge™ C18 2.5 µm 3.0 x100 mm analytical column using a mobile phase of water–acetonitrile (45:55) at a flow-rate of 0.5 mL/min. The method was evaluated using river and estuarine water spiked with rotenone (0.1–330 µg/L) and various preservation methods. The within-assay precision measured as relative standard deviation (RSD, n = 12) was 5.5 to 6.5% and the between assay precision (RSD, n = 4) was 6.5 to 7.5%. The limit of quantification was 1 µg/L, below normal piscicidal treatment rates (5 to 200 µg/L) and regulatory limits (< 2 µg/L) generally considered safe. The analysis time was 6 min/sample allowing for real-time adjustment of rotenone dosages during fish control treatments. The relatively small size (75×60×50 cm) of the LC system made it ideal for transportation and installation in remote treatment areas; it can be operated out of a small trailer in the field with electricity. Our studies indicate that the preservation of water samples with equal quantities of acetonitrile stabilizes rotenone indefinitely (> 170 days) if kept cool (4 °C) and in the dark. Although increased salinity decreased the recovery of rotenone, sample filtration with Spin-X filter membranes negated the effect.

The invasive alien ectoparasite Gyrodactylus salaris is one of the greatest threats to wild Atlantic salmon (Salmo salar) in Norway. Since its introduction in the 1970s the Norwegian Environmental Authorities have applied a piscicide based eradication strategy, using rotenone to eradicate the host species, Atlantic salmon and the parasite. After refining the methods and techniques following several unsuccessful treatments, the program has become a success and a total eradication of G. salaris from Norway now seems possible. This paper describes the methods and techniques used in this program during a large eradication operation conducted in the Rauma infection zone in central Norway using different land based peristaltic and boat mounted pumps in combination with continuous drip stations and gardening cans. The eradication was performed in 2013 and 2014 and involved six infected rivers. The largest river, the river Rauma has an anadromous section of 42 kilometers and consists of both rugged fast flowing areas and slow flowing parts characterized by laminar water currents. The piscicide, CFT-Legumine®, containing 3.3% active rotenone was applied at a dose of 1 mg/l using a range of application methods aiming to achieve concentrations of 0.033 mg/l rotenone. To ensure target concentrations were met, rotenone concentrations were monitored using liquid chromatography with UV detection in all treated river in an on-site lab on a daily basis. Target concentration was reached in all treated rivers and while investigations are ongoing, to date they indicate eradication has been effective.