Stemming from a recent freshwater invasives conference, Caffrey et al. (2014) identified ’the top 20 issues’ that relate to invasive alien species (IAS) management in Europe. With a view to complement and balance the issues highlighted in their account, we offer six important additions that relate to the marine environment. These are: preventive measures, concerns of loss of taxonomic expertise and species identity, gaps in the knowledge of certain taxa and regions, inconsistencies of terminology, need for validation of data and the importance of concentrating on pathways, and their vectors, and levels of certainty associated with these routes.

Biofouling samples from the hulls of commercial vessels using Scottish dry docks and harbours were collected to investigate which species are being transported into Scottish waters. During 2009 – 2012 a total of 29 vessels were surveyed in three dry docks and a dive team was used to sample a further six vessels at two busy North Sea harbours. The vessels were representative of those servicing the North Sea oil industry e.g. tugs, supply and safety stand by vessels and provide a good indication of the type of fouling found on vessels that typically trade in Scottish coastal waters. The biofouling consisted of typical North Sea species and four established non native species, Jassa marmorata, Caprella mutica, Austrominius modestus and Amphibalanus amphitrite were recorded. No new non native species were recorded during this study.

While considerable variation exists in ecological and economic impacts among nonindigenous species (NIS), the potential magnitude of cumulative impacts for each species increases with increasing area occupied. In the marine environment, large commercial ships have often transferred NIS across ocean basins to new continents. However, following such initial invasions, small craft (recreational and fishing boats) likely play an important role in the secondary, coastwise spread of NIS, thus increasing the geographic range and potential magnitude of impact. In this study, we assess the connectivity among bays in terms of small vessel movement and associated biofouling organisms in central California (USA), examining flux between a heavily invaded international port, San Francisco Bay (SFB), and three small marinas on the adjacent coast. We estimated vessel flux among locations, using data from 405 boater questionnaires and 4,000 transient boat records, and found a strong bi-directional connection between SFB and the nearby coastal marinas. Video surveys of 36 boats that had recently traveled revealed macrofauna on the underwater surfaces on 80% of boats, and at least 27 taxa (including 7 NIS) were present on boats sampled by SCUBA. Importantly, while we provide evidence for strong connectivity, our data most certainly underestimate the flux of vessels and cumulative transfers of organisms among these locations during this short-term study, as vessel movement data are incomplete and surveys are limited even in this small region. This study underscores the opportunities for biofouling organisms, many with limited self-dispersal capacity, to spread via small boats and suggests that effective management strategies to minimize NIS spread and impacts must address the small-boat vector.

In this paper we tested the hypothesis that potamotrygonid stingrays are expanding their distribution to novel areas via artificial passages constructed for river navigation in the Upper Paraná River basin, Southeastern Brazil. Individuals of Potamotrygon falkneri and Potamotrygon motoro were captured, fitted externally with t-bar anchor tags, and released downstream of the Jupiá Dam – a hydro power plant constructed in the 1970s that has no fish pass system, but had a navigation lock installed in 1998 for the movement of ships. A total of 182 stingrays were marked, and recaptures of individuals of both species occurred within a period of two to 12 months after the first capture, with recapture rates around 5% for P. falkneri (n=6) and 3% for P. motoro (n=2). Two individuals of P. falkneri were recaptured upstream of the Jupiá Dam, about eight kilometers from the first capture site. This fact attests to the ability of stingrays to overcome artificial barriers such as hydro power plants through navigation locks. The Upper Paraná River basin is densely populated, so the spread of potamotrygonids will increase the risk of injury from stingrays’ barbs. Their use of navigation locks is relevant for management actions, including reducing the risk of human-stingray interactions.

The genetic material (DNA fragments of cellular or extracellular origin) that organisms leave behind in nonliving components of the environment such as water, soil, or sediments is defined as environmental DNA (eDNA). Recently, the use of eDNA has been recognized as an effective method for aquatic invasive species early detection and surveillance. We developed molecular markers for eDNA detection of the African jewelfish (Hemichromis letourneuxi) in and around Loxahatchee National Wildlife Refuge, Florida. The lower limit of detection using these markers was determined as well as the effect of fish density and time on detection using controlled experiments. Specificity and sensitivity of these markers was tested in aquarium trials and also in field samples. Results showed that developed markers (probe and primers) for Taqman assays were sensitive and specific for eDNA detection via traditional and quantitative PCR methods (qPCR). The observed theoretical minimal qPCR detection level, based on standard curve analysis for this species, was approximately 0.0002 ng/uL (R2 = 0.90) at a PCR cycling threshold (CT) of 28.5–29. There was a positive and significant relationship between fish density and eDNA detection with detection probabilities ranging from 0.32–1.00 depending on fish density. A negative and significant relationship between average CT values and density further corroborated our findings that target eDNA increased with increasing fish density. Developed markers detected the presence of H. letourneuxi in the canal adjacent to but not in Loxahatchee National Wildlife Refuge. The single positive found in the canal adjacent to Loxahatchee National Wildlife Refuge showed a similar CT value to the observed average for density of three fish per aquarium.

Styela clava Herdman, 1881, is a solitary ascidian native to the Northwest Pacific, which has spread globally over the past 90 years, reaching pest levels and causing concern to the aquaculture industry in some regions. It has a relatively short-lived larval stage, spending only limited time in the water column before settling on a desirable substrate. Early detection of this species is an important step in both the prevention of its spread and of successful eradication. Here we report the development of a qPCR based assay, targeted to a region of the mitochondrial cytochrome oxidase I gene, using TaqMan® MGB, for the early identification of S. clava, post-settlement. The assay takes into account the moderately high level of haplotype diversity within this species, while also accommodating the need for species specificity. Using exemplars of closely related ascidian species, we show that our assay is specific for S. clava and is able to detect this species at low concentrations, equivalent to a single propagule. We also demonstrate, through “spike in” tests using environmental extracts, that our assay is robust to the potential inhibitors that might be found in environmental samples, which suggests this assay could have utility in the field, and may be developed further to detect larvae at an earlier stage of introduction.

The invasive bivalves Corbicula spp. and Limnoperna fortunei predominate in South American rivers. They can be sympatric in distribution, and because their larval stages are morphologically similar, monitoring them in zooplankton using microscopy protocols is often inefficient, producing ambiguous results. We designed a pair of primers to amplify a fragment of the mtDNA cytochrome c oxidase subunit I of Corbicula species. A multiplex reaction, containing the specific primer pair and a pair of universal primers (to control for the quality of the DNA in the sample) was tested with regards to specificity and ability to detect Corbicula spp. larvae in plankton samples that also contain other species in different proportions. Our molecular protocol allows for fast and accurate detection of Corbicula spp. even when concentrations of these species are low in samples, which is useful when examining large volumes of ballast/piped water. Further, the protocol is valuable for the monitoring/prospecting of early stages of the life cycle of Corbicula spp. in watersheds that have been invaded, or which are considered at risk of invasion by these species.

The long term effects of sample preservation on dreissenid veliger detection by cross polarized light microscopy (CPLM) and polymerase chain reaction (PCR) is poorly understood. This study examined how buffer and isopropanol alcohol impact veliger morphology and detection. Veliger detection by CPLM was completely inhibited after 14 days in acidic deionized (DI) water without buffer or alcohol, but veligers were still detectable by PCR. Veliger detection by CPLM increased when the pH of samples was buffered with 0.2 grams of sodium bicarbonate per 100 mL of raw water sample, but long term deterioration was not completely prevented without the addition of isopropanol alcohol and buffer. After 36 days, 100% of veligers were detected by CPLM in samples preserved with 20, 50, and 70% isopropanol alcohol and 0.2 grams of sodium bicarbonate per 100 mL. This study indicates the significant role that sample preservation plays in the accurate identification of veligers in early detection sampling.

In the present study, navigational buoys were used to monitor Dreissena polymorpha (zebra mussel), an aquatic invasive species in Otsego Lake, New York. Buoys from the north and south sites of Otsego Lake were taken out of the water on December 29 and December 31, 2012, respectively, after being in the water since April 14, 2012. All sampled mussels were frozen until further analyzed; an electronic caliper and compound microscope were used to measure shell lengths. We observed growth, settlement, and density of each colonized buoy and determined that light shielded bottom sides of the buoy had the most colonization whereas the shallowest submersed side had the least. Shell length of mussels from the south site was significantly larger than those from the north site. The mussels from the metal anchor-chain ring at the deepest end of the buoy were the largest, while no difference was found among the rest. Colonization of zebra mussels can be due to specific substrate types and amount of nutrition available in the habitat. Additionally research is recommended comparing buoy designs to determine if buoys without light shielded bottoms will be less colonized.

The Asian clam Corbicula fluminea was first recorded from the Barrow River in Ireland in April 2010. There are five separate concentrations known to exist. Four of these were found during 2010 to 2012 within Ireland’s largest river, the Shannon. The abundance and polymodal length frequencies indicate that the likely seminal site in Ireland is from the Barrow where it may have been present since, or before, 2006. There is a concern the species will continue to expand and modify aquatic communities. All concentrations are linked by a connected navigation system thereby implicating leisure craft as a pathway. However, anglers might be spreading the species since most sites where they are now known are associated with angling. This account reviews the evidence for these potential pathways, for this ‘r’ strategist. The abundance and distribution in the lower Shannon River, and possible impacts on lake ecosystems are discussed.

Riparian zones are highly susceptible to invasion by alien plants. For both invasive and non-invasive plants, water has been proved to be an important vector for seed dispersal, connecting distant populations and, therefore, contributing to the downstream expansion of invaders. However, the effect of intrinsic factors of watercourses, such as habitat quality, on the invaders’ dispersal ability is largely unknown. We compared the dispersal ability of Ailanthus altissima fruits through a release experiment in two contrasting 100 m-long stretches of a near-natural and a degraded reach of the same river. One hundred fruits were released in the centre of the channel and allowed to float during 90 minutes. Results showed that fruit retention was five times lower in the degraded reach, suggesting that the loss of complexity in the fluvial habitat structure may increase dispersal distances of A. altissima fruits in headwater streams of similar characteristics. The lack of potential depositional zones, such as pools, meanders, or biological structures in the degraded reach increased the water dispersal success of A. altissima fruits. Among the studied retentive structures, macrophytes were found to be the main natural barrier to limit dispersal of A. altissima fruits. Velocities of dispersed fruits were highly variable within each reach but did not depend on the habitat quality. This study provides reasons to consider the heterogeneity and complexity of riparian and fluvial habitat to control the dispersion of fruits of the invasive tree A. altissima.

Non-native black-tailed prairie dogs (Cynomys ludovicianus Ord, 1815) that had emigrated from a private colony were reported by property owners in rural North Central Florida in 2006. The Florida Fish and Wildlife Conservation Commission and U.S. Department of Agriculture Animal and Plant Health Inspection Service Wildlife Services (WS) initiated an assessment of the population to determine its current distribution and the feasibility of eradication. Multiple surveys, interviews with residents and observations of abandoned burrows confirmed movement of animals as far as 3 km from the source colony. WS personnel conducted an eradication program of the source colony from 23 March through 4 May 2009, primarily using a 0.17-caliber rifle along with cable restraint devices for particularly wary animals. A total of 85 prairie dogs were killed at the site of the source colony and one animal was killed on a separate property. Subsequent surveys from 2009 through 2012 confirmed the eradication was successful. Communication with the owner of the source colony and nearby residents throughout the project was critical to success.