The live marine baitworm trade harvests, packages, and ships polychaete worms and packing algae (wormweed) from Maine, USA to consumers globally, inadvertently transferring numerous invertebrates that naturally occur in the algal habitat. Here, we use a focal taxa, the globally invasive European green crab Carcinus maenas, to examine costs associated with the successful introductions via this vector and suggest an alternative packaging, already in use in Europe. We show that restricting the use of wormweed at the source could solve the problem of transferring hitchhikers without a change in product cost. However, to the extent that baitworms in wormweed are what US consumers are accustomed to receiving, alternative packing might restrict demand for baitworms, lower producer prices, and reduce quantities traded. Avoiding such economic costs and receiving the benefits of reduced likelihood of unwanted invasion at low or no cost to producers should be of interest to policymakers and practitioners tasked with protecting ecosystems.

The effects of climate change and the severe anthropization of local river systems have contributed to the alteration of ecological processes, affecting the water quality in these systems and thus generating conditions for the emergence of algal species. In this context, the object of the present study was to evaluate the potential of remote detection techniques to obtain a spectral characterization of D. geminata under controlled laboratory conditions. This would provide the basic information for the design and implementation of a monitoring and early warning system. D. geminata cells obtained from two southern Chilean river systems were cultivated in the laboratory and analysed using hyperspectral techniques to construct their spectral signatures. The results showed the feasibility of distinguishing between the presence and absence of D. geminata when it occurs in association with other diatom present in the environmental. The results could be the first step towards the design and implementation of a monitoring and early warning system to facilitate existing inspection activities.

Numerous interceptions of Perna viridis on vessels entering Western Australian waters prompted the development of a rapid field-based assessment technique for determining reproductive status and hence spawning likelihood of P. viridis. The visual assessment tool and spawning likelihood matrix were developed using correlations between laboratory-based assessments of P. viridis size, colour and egg size in combination with field-based validations from mussels collected on vessels in Western Australian waters. The spawning likelihood matrix provides an immediate indicator of whether the mussel is low, medium or high likelihood of spawning. Mussels were recorded initiating gonad tissue development from approximately 6.5 mm in length, with the mean size of mature animals 59.6 mm. There was a positive correlation between mussel size and stage of reproductive development. Gonad colour, however, appeared to be a more accurate indicator of gonad maturity than mussel size. Female mussels showed a decrease in gonad colour intensity following spawning. Mussels that scored 1 for colour (potential score 1–3) generally had a low proportion of mature eggs (< 70 % mature eggs). Over 60% of the mussels with a colour score of 2 contained 70–100% mature eggs, indicating the capacity for further spawning. Mussels were assigned an overall spawning likelihood score (through the spawning likelihood matrix) based on the proportion of the visceral mass occupied by gonad tissues (% gonad cover, value from 1–3) and overall colour of gonads (value from 1–3). The spawning likelihood score was significantly related to the percentage of mature eggs present, and hence the spawning potential of the mussel. The matrix provides an immediate indicator of the risk of spawning posed by the sample. As such, it is expected that application of the matrix in situ would enable the potential likelihood posed by P. viridis translocated on vessels to be determined quickly and efficiently.

Following the detection of the invasive killer shrimp, Dikerogammarus villosus (Dv) at two sites in the UK in September 2010, an effective biosecurity system is required to prevent further spread. This study investigated the application of several treatments as potential biosecurity measures with a view to their application on Dv-infected fomites. For each treatment, adult Dv were submerged for 15 minutes at different concentrations to determine the maximum lethal concentration, and for each effective treatment for different times to assess a minimal lethal time (LT₅₀). Sodium hypochlorite (50,000 mg/Lmg/L), FAM30® (6 ml/l), Virkon S® (1% solution) and water at high temperature (45 °C) were found to cause 100% mortality within 15-min exposure, while carbonated water caused narcosis in 100% of animals within a few seconds of exposure. Due to various drawbacks in the use of sodium hypochlorite, FAM30® and Virkon S® (e.g. health and safety, legal use) they were not recom¬mended as biosecurity treatments, whereas both water at high temperature and carbonated water showed promise. However, further investigation and field based research are required before these techniques can be fully realised as methods of control.

Surveying multiple invasive pest species at the same time can help reduce the cost of detecting new pest invasions. In this paper, we describe a new method for mapping the relative likelihood of pest invasion via plant propagation material in a geographic setting. The method simulates the invasion of a range of pest species, including arrival in an uninvaded area, spread, and survival in a novel landscape, using information on the spatial and temporal distribution of the suitable host crop species and tentative knowledge of the spread and survival capacities of the target pests. The methodology is applied to a gridded map in which each map cell represents a site in a landscape. The method uses stochastic simulations to depict plausible realizations of the invasion outcomes and estimate the distribution of pest invasion likelihood for each cell in the area of concern. The method then prioritizes the cells based on the stochastic invasion outcomes using a pairwise stochastic dominance rule and a hypervolume indicator. We demonstrate the approach by assessing the relative likelihood of pest invasion for strawberry production in Finland. Our method helps to differentiate sites in a landscape using both the estimates of pest invasion risk and their uncertainty. It can be applied to prioritize sites for plant health surveys and allocate survey resources among large geographic regions. The approach is generalizable and can be used in situations where knowledge of the harmful pest species is poor or nonexistent.

In invasive species ecology, risk identification is an essential first step of the overall risk analysis process. In this study, 24 non-native freshwater macroinvertebrate species were screened for their level of risk of invasiveness in the Dnieper, Pripyat and Neman rivers and associated basins of Belarus. Using the recently-developed Aquatic Species Invasiveness Screening Kit (AS-ISK), the threshold values of 12.25 for the Basic Risk Assessment (BRA) and 19.5 for the BRA + CCA (Climate Change Assessment) allowed identifying those species likely to be of high risk of invasiveness in the risk assessment area. For the BRA+CCA, the highest-scoring species were zebra mussel Dreissena polymorpha, spinycheek crayfish Orconectes limosus, quagga mussel Dreissena bugensis and Caspian mud shrimp Chelicorophium curvispinum, and for the BRA only signal crayfish Pacifastacus leniusculus. For all species but one (namely, fragile ancylid Ferrissia fragilis classified as low risk), the CCA resulted in an increase in score relative to the BRA, indicating that predicted future global warming conditions are likely to exacerbate the detrimental impacts of the non-native macroinvertebrates of Ponto-Caspian origin. The present application of AS-ISK confirms the predictive value of the tool, and benefits from incorporation of future climate change scenarios. This is a crucial step for the provision of guidelines for the successful management of non-native invasive species and conservation of native faunas in the (invaded) habitats of Belarus.

Environmental DNA (eDNA) is a rapid, non-invasive method for species detection and distribution using DNA deposited in the environment by target organisms. eDNA has become a recognised and powerful tool for detecting invasive species in a broad range of aquatic ecosystems. We examined the use of eDNA as a tool for detecting the invasive American signal crayfish Pacifastacus leniusculus in Scotland. Species-specific TaqMan probe and primers were designed for P. leniusculus and a robust quantitative PCR (qPCR) assay and DNA extraction protocol were developed. We investigated the detection capability for P. leniusculus from water samples in a controlled laboratory experiment and determined whether crayfish density (low = 1 crayfish 5.5 L^-1 or high = 3 crayfish 5.5 L^-1) or length of time in tanks (samples taken at 1, 3 and 7 days) influenced DNA detectability. Additionally, the persistence of DNA was investigated after P. leniusculus removal (samples taken at 1, 3 and 7 days post removal). P. leniusculus DNA was consistently detected during the entire 7-day period and higher density tanks yielded stronger positive results with lower C_t values. After removal of P. leniusculus, there was a rapid and continuous decrease in the detectability of DNA. P. leniusculus DNA could only be detected in high density tanks by the end of the 7-day period, while DNA was no longer detectable in low density tanks after 72 hours. Preliminary field experiments sampled water from three sites in winter and five sites in summer. P. leniusculus was known to be present at two of these sites. P. leniusculus was not detected at any site in winter. However, in summer, positive signals were observed at sites with known P. leniusculus, and at sites where P. leniusculus was believed to be present anecdotally, but not confirmed. All sites where crayfish were believed to be absent were negative for eDNA. Therefore, eDNA represents a promising technique to detect and monitor invasive P. leniusculus, although the presence of detectable amounts of eDNA may be season and location dependent, even where invasive crayfish are known to be present.

Lionfishes (Pterois volitans and P. miles) are now established in all regions of the Caribbean, Gulf of Mexico and the Western Atlantic. As they continue to spread and colonize, reef ecosystems could be undergoing significant changes in species composition. A successful method of control includes targeted removals, but many organized removal efforts occur on large spatial scales, or involve numerous volunteers and personnel. This study addressed the effectiveness of lionfish removal over small spatial scales on a linear coral reef in La Parguera, Puerto Rico and quantified the effort necessary to diminish and maintain low lionfish densities. Three removal events at this reef took place over one month with 11 hunters per day to cull a 14,520 m² area. Timing of recovery of lionfish density varied by area in the removal site, but an overall reduction in lionfish biomass was retained post-removal. Tagging of lionfish in non-removal sites suggested recovery to the culled area was due to re-colonization via recruitment or ontogenetic migration rather than by adult lateral immigration. No detectable effects of the lionfish removal were observed on native prey or piscivore densities. Thus, evidence from this study supports that native fish abundance may not be impacted when lionfish densities are relatively low. Removal efforts should consider lionfish density relative to the densities of the native faunal communities before committing resources to this strategy.

The environmental fate, persistence, and non-target animal impacts of traditional molluscicides for zebra, Dreissena polymorpha, and quagga, D. bugensis, mussel control led to the development of the biomolluscicide Zequanox. Although previous research has demonstrated the specificity of Zequanox, one study indicated sensitivity of salmonids and lake sturgeon, Acipenser fulvescens, following non-label compliant exposures to Zequanox. This study was conducted to evaluate sublethal and lethal impacts of Zequanox exposure on juvenile lake sturgeon and lake trout, Salvelinus namaycush, following applications that were conducted in a manner consistent with the Zequanox product label. Fish were exposed to 50 or 100 mg/L of Zequanox as active ingredient for 8 h and then held for 33 d to evaluate latent impacts. No acute mortality was observed in either species; however, significant latent mortality (P < 0.01, df = 9; 46.2%) was observed in lake trout that were exposed to the highest dose of Zequanox. Statistically significant (P < 0.03, df = 9), but biologically minimal differences were observed in the weight (range 20.17 to 21.49 g) of surviving lake sturgeon at the termination of the 33 d post-exposure observation period. Statistically significant (P < 0.05, df = 9) and biologically considerable differences were observed in the weight (range 6.19 to 9.55 g) of surviving lake trout at the termination of the 33 d post-exposure observation period. Histologic evaluation of lake trout gastrointestinal tracts suggests that the mode of action in lake trout is different from the mode of action that induces zebra and quagga mussel mortality. Further research could determine the sensitivity of other salmonid species to Zequanox and determine if native fish will avoid Zequanox treated water.