Incorporating ecosystem changes from non-indigenous species (NIS) is an important task of maritime spatial planning. Maritime spatial planning requires a framework that emphasises ecological functioning in a state of dynamic change, including changes to ecosystem services from functions introduced by new NIS. Adaptable modelling toolsets should be developed that can readily incorporate knowledge of new NIS. In the Baltic Sea, recent NIS examples are the North American mud crab Rhithropanopeus harrisii and the Ponto-Caspian round goby Neogobius melanostomus. We performed environmental niche modelling that predicted N. melanostomus will spread across large areas of the Baltic Sea coast while R. harrisii will be limited to regions with high temperature and low salinity conditions. We then performed a meta-analysis on literature showing effects in the Baltic Sea from these NIS and calculated the standardised effect-sizes on relevant ecosystem services. Half the impacts identified for N. melanostomus were considered to increase ecosystem service outcomes, while all R. harrisii impacts caused apparent decreases. Effect coefficients were incorporated into an online impact assessment tool developed by the Estonian Marine Institute. Users with or without science training can use the portal to estimate areas impacted and changes to natural assets (km2) caused by these NIS and cumulative effects from other pressure-types. Impact estimates are based on best available knowledge from manipulative and correlative experiments and thus form a link between science and management. Dynamic modelling techniques informed from varied ecological and methodological perspectives will effectively advise spatial planners about rapid maritime changes and mitigationactions to reduce NIS impacts especially in the focus areas.
Managing invasive alien species is particularly challenging in the ocean mainly because marine ecosystems are highly connected across broad spatial scales. Eradication of marine invasive species has only been achieved when species were detected early, and management responded rapidly. Generalized approaches, transferable across marine regions, for prioritizing actions to control invasive populations are currently lacking. Here, expert knowledge was elicited to prioritize 11 management actions for controlling 12 model species, distinguished by differences in dispersion capacity, distribution in the area to be managed, and taxonomic identity. Each action was assessed using five criteria (effectiveness, feasibility, acceptability, impacts on native communities, and cost), which were combined in an ‘applicability’ metric. Raising public awareness and encouraging the commercial use of invasive species were highly prioritized, whereas biological control actions were considered the least applicable. Our findings can guide rapid decision-making on prioritizing management options for the control of invasive species especially at early stages of invasion, when reducing managers' response time is critical.
Lionfish (Pterois volitans/miles) are an invasive species in the Western Atlantic and the Caribbean. Improving management of invasive lionfish populations requires accurate total biomass estimates, which depend on accurate estimates of allometric growth; sedentary species like lionfish often exhibit high levels of spatial variation in life history characteristics. We reviewed 17 published length-weight relationships for lionfish taken throughout their invasive range and found regional differences that led to significant misestimates when calculating weight from length observations. The spatial pattern we observed is consistent with findings from other studies focused on genetics or length-at-age. Here, the use of ex situparameter values resulted in total biomass estimates between 76.2% and 140% of true observed biomass, and up to a threefold under- or overestimation of total weight for an individual organism. These findings can have implications for management in terms of predicting effects on local ecosystems, evaluating the effectiveness of removal programs, or estimating biomass available for harvest.
Non-native species are a major driver of environmental change. In this study we assessed the ecological impact of the “worst” non-native species and the associated scientific and media publications through time to understand what influences interest in these species. Ecological effect was based on a qualitative assessment reported in research publications and additional searches of the scientific and media attention were conducted to determine published articles and assess attention. We did not detect a relationship between the number of publications for a non-native species and the magnitude of the ecological effects of that species or the number of citations. Media coverage on non-native species was low, only evident for less than 50% of the non-native species assessed. Media coverage was initially related to the number of scientific publications, but was short-lived. In contrast, the attention to individual non-native species in the scientific literature was sustained through time and often continued to increase over time. Time between detection of the non-native species and the scientific/media attention were reduced with each successive introduction to a new geographic location. Tracking publications on non-native species indicated that media attention does seem to be associated with the production of scientific research while scientific attention was not related to the magnitude of the ecological effects.
The spread of non-indigenous species is a global phenomenon that affects most ecosystems. Although invasion biology is a well-investigated discipline, there are still gaps in knowledge that may prevent obtaining a complete and realistic picture of the impact and scale of biological invasions. It is important, indeed, to distinguish between knowledge (reality) and what is taken for granted (myth). This study focused on the state of knowledge regarding the non-indigenous marine species currently present in the Mediterranean Sea. On the one hand, the information is overall exhaustive as regards the total number of non-indigenous species, their traits, invasiveness potential and vectors of spread. In particular, the Mediterranean is one of the best-monitored seas thanks to the international networks of marine scientists. On the other hand, however, scientific evidence does not suffice to draw general conclusions on the real magnitude of the ecological impact of non-indigenous species. Most studies, indeed, have investigated very few invasive species, generally at local scale, while the long-term effects of non-indigenous species are poorly known. The myth does not consist in stating that there is an ecological impact on Mediterranean marine biodiversity but in taking for granted that we are currently able to assess the magnitude of this impact. These uncertainties have inevitable consequences at decision-making and management level that could be mitigated through open interaction between stakeholders involved in policy and science on the one hand, and society on the other hand.
Mitigating the negative impacts of invasive lionfish (Pterois volitans/milescomplex) is a top priority for marine reef fisheries management, with human removals considered the most viable approach to population control. Control efforts via diver spearfishing removals have annually removed tens of thousands of lionfish throughout their invasive range, but the effectiveness of removal efforts to remove 100% or achieve target lionfish densities in a given reef system has not been fully evaluated. Accounting for detection and removal efficacy is necessary for developing and evaluating lionfish management targets, as population- and community-level effects of lionfish removals may be diminished by undetected lionfish remaining in the system. This study quantified lionfish detection, catchability, and removal efficiency to evaluate the effectiveness of lionfish surveys and removal efforts on northern Gulf of Mexico (nGOM) artificial and natural reefs. Detection was assessed during crepuscular and midday time periods via diver and remotely operated vehicle (ROV) video surveys, with covariates for time of day and survey methodology assessed using generalized linear mixed models. Catchability and removal efficiency were estimated via depletion models based on serial removals via spearfishing on 6 artificial reefs and 9 natural reefs. A priori, we had expected lionfish detection to be higher during crepuscular periods given lionfish in the Caribbean and in their native range have been shown to forage more actively away from reefs then. However, we found lionfish detection was not significantly different between midday and crepuscular periods. Survey methodology affected detection, with 24% fewer lionfish being detected via ROV surveys versus diver surveys at artificial reefs and 72% fewer lionfish detected via ROV surveys at natural reefs. Therefore, density estimates on nGOM natural reefs, which constitute of >99% of the region’s habitat, may be higher than previously reported and problematic for lionfish management. Mean catchability for spearfishing lionfish was 0.88 on artificial reefs and 0.69 on natural reefs standardized for area. Mean removal efficiency for the first removal event was 87% on artificial reefs and 67% on natural reefs, higher than removal efficiency computed for Caribbean reefs (47%). Incomplete detection and <100% removal efficiency, in concert with density-dependent processes, may explain recent findings that sustained lionfish removal efforts had no discernible positive impacts on native reef fish communities.
The human-mediated introduction of marine non-indigenous species is a centuries- if not millennia-old phenomenon, but was only recently acknowledged as a potent driver of change in the sea. We provide a synopsis of key historical milestones for marine bioinvasions, including timelines of (a) discovery and understanding of the invasion process, focusing on transfer mechanisms and outcomes, (b) methodologies used for detection and monitoring, (c) approaches to ecological impacts research, and (d) management and policy responses. Early (until the mid-1900s) marine bioinvasions were given little attention, and in a number of cases actively and routinely facilitated. Beginning in the second half of the 20th century, several conspicuous non-indigenous species outbreaks with strong environmental, economic, and public health impacts raised widespread concerns and initiated shifts in public and scientific perceptions. These high-profile invasions led to policy documents and strategies to reduce the introduction and spread of non-indigenous species, although with significant time lags and limited success and focused on only a subset of transfer mechanisms. Integrated, multi-vector management within an ecosystem-based marine management context is urgently needed to address the complex interactions of natural and human pressures that drive invasions in marine ecosystems.
To effectively tackle the challenge of biological invasions through targeted strategies and mitigation measures, managers and policy makers require adequate reporting and flow of information. For this reason, the European ‘Natura 2000’ network of protected areas, which is the main conservation tool of the European Union, is supported by a standardized database. All threats to biodiversity are supposed to be reported in sufficient detail through that database. We compared the reported threats by ‘invasive non-native species’ in the Natura 2000 database with the actual cumulative impacts of invasive alien species on marine habitats in the Mediterranean using the CIMPAL index (Cumulative IMPacts of invasive ALien species). CIMPAL estimates cumulative impact scores on the basis of the distributions of invasive species and ecosystems, and both the documented magnitude of negative ecological impacts and the strength of such evidence. We showed that the threat of invasive alien species is substantially under-reported in the official documentation. Specifically, among the 1455 marine sites of the network, no threat was officially reported in one third of the sites. The threat of biological invasions was only reported in 154 sites, despite negative impacts by invasive alien species being predicted for 98% of all sites when using CIMPAL. In fact, in the subgroup of sites where no threats have been officially reported, the impacts predicted by CIMPAL were the highest. Such, inadequate and insufficient reporting of threats in the Mediterranean marine Natura 2000 sites presents a significant obstacle to the flow of accurate information needed to support conservation policies and marine management.
The Great Lakes are one of the most invaded aquatic ecosystems in the world, and the spread of fish pathogens and aquatic invasive species (AIS) has become a serious issue for fishery management in the Great Lakes. Our study applies the Drivers-Pressures-State-Impacts-Responses model (DPSIR) to identify social-ecological linkages in the spread of pathogens and AIS by anglers, boaters, and bait dealers in the Great Lakes. We developed a conceptual DPSIR model based on input by staff members in governmental agencies and non-governmental organizations that have been involved in the management of pathogens and AIS. The integration of managers' input to develop the model is a novel approach for understanding fisheries. Most previous studies using the DPSIR framework did not account for natural resource managers' input even though the DPSIR framework is frequently applied to provide information to these groups. The identified relationships in our model provide multiple entry points for empirical, interdisciplinary research. These studies would help understand the effectiveness of management responses to change human behaviors, and to understand and predict changes in the Great Lakes ecosystem and fishery. The model could also be used to promote understanding of the impacts of pathogens and AIS on the fishery, and to increase awareness of human behaviors that contribute to the continued spread. Future studies could further expand or replicate the model with input by other stakeholder groups such as bait dealers and/or anglers and boaters to identify if these groups share an understanding of the management problem and responses.