In June 2012 a single non-native snakehead fish was captured by local officials in a small pond within an urban park in Burnaby, British Columbia. This single snakehead fish garnered significant attention in the local and national media. DNA analysis determined it to be a blotched snakehead (Channa maculata) or possibly a hybrid; a warm water species native to China and Vietnam which is commonly sold in the live food fish trade, and occasionally kept by hobbyists. By collecting prey items from the pond and snakehead specimens from fish markets we used a novel stable isotope approach to estimate how long it had been since the snakehead had been released into the pond. Using a diet-switching tissue turnover model, we estimated that the snakehead was in the pond between 33 and 93 days. Subsequently, provincial legislation was amended to ban all species of snakehead fish, as well as numerous other potentially invasive fish and invertebrate species.

Increasing legislative drivers demand the removal or modification of riverine barriers to enhance habitat connectivity for fish; however there is also concern that greater connectivity will hasten the spread of aquatic invaders such as the signal crayfish (Pacifastacus leniusculus). Passive Integrated Transponder (PIT) telemetry was used to assess passage of signal crayfish (n=392) over a typical low-head riverine structure, a flow gauging weir, during a 17 month period. Sixty percent of tagged crayfish were detected, with greatest crayfish activity associated with high water temperatures and long day lengths. The study weir reduced upstream crayfish movements, with 45% less passages than in the control stretch with no weir, but there was no difference in the downstream direction. We found sex and size related differences in crayfish movement patterns with male crayfish more likely to successfully ascend the weir, and larger crayfish to descend the weir. Although increased fluvial connectivity will benefit migratory fish species, we suggest that the removal or modification of even quite minor, low-head structures such as the one investigated could hasten the upstream spread of signal crayfish.

This paper reports the use of chlorophyll fluorescence analysis (CFA) to determine the effects of herbicides on photosynthetic activity in Arundo donax L. (giant reed). A field experiment was conducted with five systemic herbicides. Glyphosate 36% was applied in each of the following ways; 1) on adult mass of giant reed plants (3–4 metres in height), 2) on sprouts after initial cutting (80 cm in height) and glyphosate 54% was applied by injection into the stem with full-strength product. The other herbicides were applied on giant reed after the initial sprouting following cutting, on-label application rate. The CFA showed that glyphosate 36% applied on adult mass of plants at 10 L a.i. ha-1 had a significant effect (70% reduction) on photosynthetic activity 60 days after treatment (DAT). Glyphosate 36% at 4 L a.i ha-1 applied on sprouts resulted in 50% reduction and glyphosate 54% at 4 L a.i ha-1 applied by injection into the giant reed stems reduced their photosynthetic activity by 60%. Profoxydim 20% at 0.75 L ha-1 caused a 50% reduction at 60 DAT, cyhalofop-butyl 20% and penoxsulam 2.04% reduced 12 and 15% respectively, and azimsulfuron had no significant effect on photosynthetic activity of giant reed. Visual evaluations of giant reed presence showed similar results at 168 DAT. These results show that CFA could be used to measure the response of invasive plants to herbicides, and that glyphosate 36%, and possibly profoxydim 20%, might be used as an integrated control of giant reed.

The Indo-Pacific coral Tubastraea micranthus recently invaded a region near the Mississippi River mouth, Gulf of Mexico, and its populations have been expanding. Its congener, Tubastraea coccinea, invaded during the 1940s and is now common in the western Atlantic. Accessibility is important in determining whether an invasive species can be controlled/eradicated. In the marine environment, depth limits accessibility. We assessed the depth distribution of T. micranthus and T. coccinea on 15 oil/gas platforms using remotely operated vehicles (ROVs). Pooled data indicated that T. micranthus extends to 138 m and probably deeper, while T. coccinea is generally limited to < 78 m. Average depths for T. micranthus were shallower west of the Mississippi River, in its plume, and deeper towards the east. Tubastraea coccinea exhibited a similar geographic depth-distribution pattern, but shallower and subtler. Broad geographic patterns were similar whether using density or percent-cover data for analysis. When considering individual platforms, T. micranthus often reached the bottom and sometimes occurred at depths >138 m. Tubastraea coccinea were limited to shallow waters on all platforms. Detailed depth distribution patterns varied significantly between analyses using density and percent-cover data, with density probably indicating colonization rates, and percent-cover colony growth. Depth limitation by T. coccinea may be associated with food availability rather than light since it is azooxanthellate. The occurrence of T. micranthus in deep water will most likely make any control or eradication efforts difficult, due to cost and a rapid rate of population expansion.

The invasion process can be described as a succession of stages initiated by the transport of organisms from their native range to a new area where they persist, proliferate and spread. It is important to monitor the demographic development of invaders for management purposes. This study focuses on the different stages of population development during the invasion process and underlines the importance of understanding and monitoring the ‘persistence phase’. The distribution of Hemigrapsus sanguineus (Asian shore crab) in the English Channel, along the French coast, was first undertaken in 2008. In 2010, 35 sites were surveyed and it appeared that the abundance of this species had already established a 2–5 fold increase since 2008. The present study presents the geographical distribution of H. sanguineus in 2011 and 2012 which includes a further 39 sites (72 sampling stations in 2012). All populations observed during previous years persisted in 2011 and 2012. In 2012, H. sanguineus was detected at 61 sites; 36 intensely colonised (including 3 newly colonised sites compared to 2011); 22 had trace numbers and 3 sites had ‘proven presence’. In addition to males with carapaces up to 39 mm width (CW), abundances increased by a factor of 2 since 2010, which testifies for the naturalized status of the species along the French coast of the English Channel. Since 2008, La Hougue proved to be the most abundantly colonised site along the French coast. By 2011 it had an average density of 101±19 ind.m-2, with an abundance of 258±54 individuals (under 30 boulders). Populations were subsequently halved in 2012. Increasing densities and abundances recorded between 2008 and 2011 at la Hougue suggest that H. sanguineus had reached the ‘expansion phase’, but the dynamics of H. sanguineus populations at the most colonised sites (12 sampling sites with abundance >200 individuals under 30 boulders), suggest that maximum values had already peaked and that the ‘persistence phase’ was probably reached. The implementation of pluri-annual surveys seems of prime importance to correctly evaluate population dynamics of alien species.

The control of marine pest populations in transport hubs has the potential to contain or limit spread by minimizing the infection of vessels and other vectors. We draw on New Zealand experiences with eradication or population control attempts on two marine pests, the Asian kelp Undaria pinnatifida Harvey Suringar and the colonial ascidian Didemnum vexillum Kott, to evaluate the extent to which vector infection was mitigated by management efforts. For both species we compare two levels of effort: sustained control involving intensive regional-scale eradication programs, and shorter-duration less intensive efforts that we refer to as partial control. The mean monthly proportion of vessels infected by Undaria was ~1% in two regions where sustained control reduced densities in marine habitats to 1–5% of the pre-treatment population. By contrast, 39% of vessels were infected during a partial control effort, which was comparable to the proportion of vessels infected in four ports where Undaria populations were not managed. For Didemnum, a reduction of the population to < 0.1% of the pre-treatment level almost completely negated vessel infection, to the extent that few vessels were implicated in the further spread of Didemnum while sustained control was in place. By contrast, partial population control led to limited benefit in terms of vector risk reduction. More importantly, a cessation or reduction in population control efforts resulted in relatively rapid vessel re-infection. Both case studies illustrate that intensive control of marine pest populations can greatly reduce the infection of susceptible vectors, but achieving such an outcome requires an indefinite commitment of resources, and may be impractical for multiple pest species or multiple infested locations. Although slowing the spread of marine pests can lead to demonstrable benefits, for population control to have greater practicality and stakeholder support, there is a need for socially acceptable and affordable control tools that are effective across relatively large spatial scales.

Biofouling on the hulls of recreational boats kept on swing moorings and marina berths poses a risk of transporting invasive species. A survey of 360 boats was undertaken of both mooring types at six sites near Auckland, New Zealand by visual observation from the waterline and underwater video. Both methods showed that the boats on swing moorings had more biofouling than those in berths (p < 0.001), and the video found more biofouling than visual observation (p < 0.001). A survey of boat owners found that boats on swing moorings moved at lower speeds (a function of different vessel types), making their speed insufficient to dislodge biofouling and potentially increasing their biosecurity risk. Five invasive marine species were known in the study area and the video images suggested that some of these and other invasive marine species were growing on boat hulls. About 8,700 recreational boats may be moored in the region, indicating that they have the potential to disperse invasive marine species beyond their present range.