The Suez Canal is the main pathway of introduction of non-indigenous species into the Mediterranean Sea. The successive enlargements of the Suez Canal have raised concern over increasing propagule pressure resulting in continuous introductions of new non-indigenous species and associated degradation and loss of native populations, habitats and ecosystem services. The United Nations Environment Programme (UNEP) through its Barcelona Convention has pledged to protect the biological resources, habitats and ecosystem services of the Mediterranean Sea, and have committed to spatial protection measures. Yet, UNEP shied away from discussing, let alone managing, the influx of tropical non-indigenous biota introduced through the Suez Canal. Surveys, funded by the Regional Activity Centre for Specially Protected Areas (UNEP RAC/SPA), established by the Contracting Parties to the Barcelona Convention, revealed that marine protected areas in the eastern Mediterranean have been inundated by these non-indigenous species, and may in fact function as hubs for their secondary dispersal. We call attention to the failure of an environmental policy that left the entire Mediterranean Sea prone to colonization by highly impacting non-indigenous species, including poisonous and venomous ones. Scientific research has been documenting this bioinvasion for over a century, yet beyond the ambit of marine scientists there is a lack of awareness of the scale of Mediterranean-wide consequences and scant appetite to enact the necessary environmental policies.

Habitat modification and the introduction and establishment of non-indigenous species (NIS) are two of the greatest threats to global biodiversity. Human modifications of marine habitats include the introduction of boating infrastructure, coastal defences and offshore energy installations that are occurring at an increasing rate. These artificial structures are now widely recognised as providing opportunities for the establishment and dispersal of non-indigenous fouling species in new regions. This is driving increased interest into how structures might be designed and built to limit their suitability for invasive species. At the same time the potential for artificial habitats to provide habitat to native and threatened species means that the control of NIS on these structures should not just rely on antifouling. Green or eco-engineering aims to incorporate ecological theory and principles into the design of engineered structures. When combined with other management strategies that aim to increase the resistance of recipient environments there is the potential to enhance practical barriers against invaders in an increasingly developed ocean. Here I explore examples of NIS facilitation by artificial structures and the ecological theories that could be used to reduce opportunities for NIS establishment and spread. Examples include (1) manipulating the physical and chemical properties of structures to enhance native recruitment over NIS, (2) enhancing resource use of structures by native species through “pre-seeding”, (3) providing opportunities for native grazers and predators to easily access structures, and (4) considering the timing of construction/maintenance/decommissioning for artificial structures such that resources are not made available when propagule pressure is also high. These examples are not exhaustive, but rather provide a discussion point for managers of biological invasions to generate further research and application over larger spatial scales.

This study demonstrates the importance of selecting the appropriate treatment regime to maximize productivity and profit in mussel farms affected with the infestation of Ciona intestinalis. This study also showed that the profitability associated to a treatment regime is primarily related to the mussel biomass being harvested. Results indicated that initiating treatment early in the season (July) and treating another 2 or 3 times on a monthly basis had the greatest effect on reducing tunicate numbers and size and enabling greater mussel productivity and farm profitability. Beginning treatment when tunicates are small was also demonstrated to be a significant part of a profitable treatment strategy. While the cost of treatment remains a relatively minor expense, the increase in mussel biomass at harvest, and hence grower profitability are considerably higher.

While screening-level risk assessment (SLRA) tools for non-indigenous species generally provide managers with reliable information for decision making (e.g., a proposed species introduction should be allowed or rejected), the results are affected by several sources of uncertainty. In particular, model uncertainty, related to the influence of factors/questions included in SLRA tools has rarely been addressed. Here we undertook an investigation of model uncertainty using a detailed evaluation of the contribution of questions included in the Canadian Marine Invasive Screening Tool (CMIST) and determined if the tool can be made more accurate through a series of optimization procedures. Accuracy was defined as the fit between assessment scores and the results of an expert opinion survey of risk posed by 48 marine invertebrate species known to have been introduced into Canadian coastal waters. We first measured the contribution of each question to accuracy and removed the ones that did not improve the fit. We then derived optimal weights that adjust the contribution of each question to maximize accuracy. Eight of 17 questions were found not to improve accuracy, or even decreased it; removing these questions, followed by addition of weights made the tool gradually more accurate when all species were included. However, an independent cross-validation test showed these weights to be too variable to consistently improve fit; this was probably related to the relatively small number of species included in the tests. Tools that have previously been tested using a large number of species should be used to determine if addition of optimal weights can improve independent predictions. The evidence that risk assessment tools are over-parameterized is building and we suggest that currently used tools would benefit from a detailed evaluation of the value of questions they include. Careful selection of questions and weights, based on accuracy improvement and other elements (e.g., organizational mandate) could greatly benefit SLRA tools, by providing more accurate estimations of risk and accelerating assessments.

In the 1980s two invasive azooxanthellate corals, Tubastraea coccinea Lesson, 1829 and Tubastraea tagusensis Wells, 1982 (Dendrophyllidae) invaded the Southwest Atlantic. In Brazil, they were first reported from fouling on oil platforms’ and have expanded their range along 3,500km of the coastline. The Sun-Coral Project (PCS) was launched in 2006 as an outreach program aimed at the restoring marine ecosystems, mitigating the environmental damage and redressing the social and economic impacts caused to coastal communities by the sun corals. We train collectors to manually remove the corals from the seabed and earn extra income by selling the skeletons, which are used in craftwork sold to tourists. Engaging human coastal communities in management allowed it to contribute to local sustainable development. The aim of this study was to critically evaluate the first ten years of PCS as a management initiative. We 1) analysed the contribution of PCS to scientific knowledge by carrying out a systematic literature search; 2) reviewed the contribution of the regional and community monitoring program to management planning; 3) analysed management results; 4) identified social-economic effects of extra-income; 5) synthesized information regarding the structure of PCS and the role of environmental education, capacity building, training and communication. PCS is structured into training, environmental restoration, extra income and sustainability, communication, monitoring and research programs. Environmental education is present across all programs. A hotline receives new records, a task force is available for first response management and training, a Visitor’s Center was created for communication and as a field base, and a National Sun Coral Records Database was created to gather all information. The PCS Database compiled historical records and demonstrated that the sun corals continued to expand along the Brazilian coastline during the study period (2006–2016). PCS’s Research, Development and Innovation (R&D&I) Network (14 institutions, 35 members) contributed to knowledge producing 70% of publications dealing with the sun corals in Brazil. Monitoring was able to map distribution and range expansion at 326 monitored sites over four regions. Twenty five different types of outreach actions were identified which directly affected 143,000 people. Two hundred and thirty thousand sun-coral colonies (8.5 T) have been manually removed through 165 control and eradication actions. Eighty six percent of the 22 collectors and their 80 family members said their lives improved due to the extra income. The results presented here demonstrate that PCS has created a science-based, community supported, conservation initiative which provides information for government, the scientific community and stakeholders, as well as extra-income, methods and human resources for monitoring and managing the sun corals invasion.

The scleractinian coral Tubastraea coccinea is native to the Pacific Ocean, and it is the first documented hard coral to have invaded the Western Atlantic Ocean. Along the Brazilian coast, this species was documented in the late 1980s on artificial substrates, but currently, T. coccinea is also observed in the natural environment. Previous studies reported that T. coccinea can alter the structure of the native community and can cause social and economic impacts. However, relatively little information is available about control methods and strategies focusing on this coral as the target species. This study aims to evaluate the effectiveness of sodium hypochlorite (NaClO) exposure on T. coccinea colony mortality and to determine the lowest concentration required to kill this species. The experiments were conducted in controlled laboratory conditions. Colonies were exposed to sodium hypochlorite solutions (2.5% active chlorine) at concentrations of 2, 20, 50, 100, 150 and 200 ppm. The control treatment exposed colonies to only seawater. Colonies were monitored over seven days or until death. Concentrations equal to or higher than 20 ppm were harmful to T. coccinea, causing several types of damage and, eventually, mortality of the colonies. The time needed to kill all the colonies was 108 hours in 20 ppm sodium hypochlorite solution, 72 hours in 50 and 100 ppm, 5 hours in 150 ppm and 3 hours in 200 ppm. Our results showed that the sodium hypochlorite solution was effective for killing T. coccinea colonies. In addition, at 150 ppm and 200 ppm we obtained the best results since the colonies achieved 100% mortality in a short period of time. Therefore, sodium hypochlorite is a potential option to be applied in the management and control of this invasive coral in restricted areas, in both artificial and natural substrates.

Determining the feasibility of controlling marine invasive algae through removal is critical to developing a strategy to manage their spread and impact. To inform control strategies, we investigated the efficacy and efficiency of removing an invasive seaweed, Sargassum horneri, from rocky reefs in southern California, USA. We tested the efficacy of removal as a means of reducing colonization and survivorship by clearing S. horneri from 60 m² circular plots. We also examined whether S. horneri is able to regenerate from remnant holdfasts with severed stipes to determine whether efforts to control S. horneri require the complete removal of entire individuals. The experimental removal of S. horneri in early winter, just prior to the onset of reproduction, reduced recruitment in the next generation by an average of 54% and reduced survivorship to adulthood by an average of 25%. However, adult densities one year after clearing averaged 83% higher in removal plots and 115% higher in control plots. We attribute these higher densities to anomalously warm water associated with the 2015–16 El Niño that reduced native canopy-forming algae and enhanced the recruitment and survival of S. horneri. We did not find any evidence to suggest that S. horneri has the capacity to regenerate, indicating that its control via removal does not require the tedious task of ensuring the removal of all living tissue. We developed efficiency metrics for manual removal with and without the aid of an underwater suction device and found the method with maximum efficiency (biomass removed worker^-1 hr^-1) varied based on the number of divers and surface support workers. Our findings suggest that controlling S. horneri via removal will be most effective if done over areas much larger than 60 m² and during cool-water years that favor native algae. Such efforts should be targeted in places such as novel introduction sites or recently invaded areas of special biological or cultural significance where S. horneri has not yet become widely established.

Introduced Marine Pests (IMP, = non-indigenous marine species) prevention, early detection and risk-based management strategies have become the priority for biosecurity operations worldwide, in recognition of the fact that, once established, the effective management of marine pests can rapidly become cost prohibitive or impractical. In Western Australia (WA), biosecurity management is guided by the “Western Australian Prevention List for Introduced Marine Pests” which is a policy tool that details species or genera as being of high risk to the region. This list forms the basis of management efforts to prevent introduction of these species, monitoring efforts to detect them at an early stage, and rapid response should they be detected. It is therefore essential that the species listed can be rapid and confidently identified and discriminated from native species by a range of government and industry stakeholders. Recognising that identification of these species requires very specialist expertise which may be in short supply and not readily accessible in a regulatory environment, and the fact that much publicly available data is not verifiable or suitable for regulatory enforcement, the WA government commissioned the current project to collate a reference collection of these marine pest specimens. In this work, we thus established collaboration with researchers worldwide in order to source representative specimens of the species listed. Our main objective was to build a reference collection of taxonomically vouchered specimens and subsequently to generate species-specific DNA barcodes suited to supporting their future identification. To date, we were able to obtain specimens of 75 species (representative of all but four of the pests listed) which have been identified by experts and placed with the WA Government Department of Fisheries and, where possible, in accessible museums and institutions in Australasia. The reference collection supports the fast and reliable taxonomic and molecular identification of marine pests in WA and constitutes a valuable resource for training of stakeholders with interest in IMP recognition in Australia. The reference collection is also useful in supporting the development of a variety of DNA-based detection strategies such as real-time PCR and metabarcoding of complex environmental samples (e.g. biofouling communities). The Prevention List is under regular review to ensure its continued relevance and that it remains evidence and risk-based. Similarly, its associated reference collection also remains to some extent a work in progress. In recognition of this fact, this report seeks to provide details of this continually evolving information repository publicly available to the biosecurity management community worldwide.

Tolerance to fluctuating environmental conditions is regarded as a key trait of successful marine invasive species as it presumably promotes survival in recipient habitats, which are often anthropogenically impacted systems such as harbours. Little is known, however, about how transport of fouling organisms on ship hulls influences the condition of the transported individuals and how this is related to their tolerance to environmental stress. We investigated the influence of transport on a ship hull on the ability of Asian green mussels, Perna viridis, to survive low concentrations of dissolved oxygen (0.5 and 1 mg/l DO). This was done by comparing the performance under stress in mussels from a eutrophic habitat in Jakarta Bay to that of mussels that had spent their lifetime on a passenger ferry crossing the Indonesian Archipelago from Jakarta in the west to West Papua in the east. We found that the mussels that came from the eutrophic habitat survived twice as long as mussels from the ferry when exposed to low oxygen concentrations. Mussels collected from the ferry, however, had a generally higher byssus production under experimental conditions, which can be attributed to their life on a moving object where they are exposed to drag. We suggest that Jakarta Bay mussels survived oxygen stress longer because they had higher Body Condition Indices than their conspecifics from the ship hull and thus had more energy available for stress compensation. These results show that transport on ship hulls can weaken the robustness of P. viridis, if the journey leads the ship through areas of low food supply for mussels, if the stopovers in eutrophic coastal ecosystems are short and if the sailing times are long (several weeks). This finding might explain the lack of establishments of P. viridis in tropical areas of Australia, from where repeated incursions have been reported.

The invasive European green crab, Carcinus maenas, has been present on the west coast of Vancouver Island since at least 1998. Annual trapping was conducted between 2010 and 2014 at Pipestem Inlet, British Columbia, Canada to determine if depletion is a potential mechanism to eradicate or control established populations. Catch per unit effort (CPUE) decreased over time within years suggesting depletion was reducing population abundance but this trend was not apparent between years suggesting control measures may be of limited utility over the longer term. For example, there was an increase in population size between 2010 and 2012 despite annual depletion efforts, likely due to good recruitment. Although the effects of depletion efforts on population size are less apparent, these events have significantly altered the demographics of the population at Pipestem Inlet, including decreased carapace width. Also, catch rates generally showed a bias towards female crabs among years. These demographic changes could have implications for the continuing green crab invasion on the west coast of North America, especially northward spread.

The European green crab, Carcinus maenas, was initially discovered in North Harbour, Placentia Bay, Newfoundland in 2007. Reproductive biology of this sub-arctic population was investigated and compared to populations in other areas of Atlantic Canada where invasions have occurred in recent decades in different environments. Histological and gonadosomatic carapace width value (GCW) analyses showed that male green crab are mature at carapace width (CW) 32 mm and females are mature at 37 mm. Placentia Bay reproductive females were smaller, spend a shorter time ovigerous, and release larvae once annually in temperatures colder than similar green crab populations in other areas of Atlantic Canada. Information on reproductive strategies in invaded areas is critical in designing mitigation and management plans to target spawning threshold levels in these green crabs.

To determine the presence, or extent and spread, of marine pests is often difficult and decisions on allocating limited sampling effort need to be made using available information. This study presents a robust structured methodology to develop a detection survey for the marine pest Sabella spallanzanii. The design of the detection survey used modelled hydrodynamics of the area and expert knowledge on settlement characteristics for Sabella. Habitat suitability for settlement was defined based on expert opinion elicited using the Analytical Hierarchy Process (AHP) technique and a self-administrated questionnaire. Zones for Sabella settlement were then identified by overlaying suitable habitat areas and hydrodynamic patterns of potential larval propagule dispersal. Settlement zones were assigned a risk/likelihood ranking to ensure available surveying effort was allocated efficiently over a potentially wide settlement area. This design was shown to be successful in detecting Sabella. Provided underlying hydrodynamic information is available, the structured approach to pest species detection presented here could readily be applied to develop surveillance plans for other broadcast spawning marine pests.