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.
Biological invasions threaten biodiversity in terrestrial, freshwater and marine ecosystems, requiring substantial conservation and management efforts. To examine how the conservation planning literature addresses biological invasions and if planning in the marine environment could benefit from experiences in the freshwater and terrestrial systems, we conducted a global systematic review. Out of 1,149 scientific articles mentioning both “conservation planning” and “alien” or any of its alternative terms, 70 articles met our selection criteria. Most of the studies were related to the terrestrial environment, while only 10% focused on the marine environment. The main conservation targets were species (mostly vertebrates) rather than habitats or ecosystems. Apart from being mentioned, alien species were considered of concern for conservation in only 46% of the cases, while mitigation measures were proposed in only 13% of the cases. The vast majority of the studies (73%) ignored alien species in conservation planning even if their negative impacts were recognized. In 20% of the studies, highly invaded areas were avoided in the planning, while in 6% of the cases such areas were prioritized for conservation. In the latter case, two opposing approaches led to the selection of invaded areas: either alien and native biodiversity were treated equally in setting conservation targets, i.e., alien species were also considered as ecological features requiring protection, or more commonly invaded sites were prioritized for the implementation of management actions to control or eradicate invasive alien species. When the “avoid” approach was followed, in most of the cases highly impacted areas were either excluded or invasive alien species were included in the estimation of a cost function to be minimized. Most of the studies that followed a “protect” or “avoid” approach dealt with terrestrial or freshwater features but in most cases the followed approach could be transferred to the marine environment. Gaps and needs for further research are discussed and we propose an 11-step framework to account for biological invasions into the systematic conservation planning design.
Marine litter has been considered a potential transport vector of non-indigenous species. In this study developed in Tjärnö (Sweden), at the entry of the Baltic Sea, the communities inhabiting coastal litter and natural substrates (N = 5448 macroorganisms) were monitored from eight sites of different ecological conditions. The results showed that litter can support high densities of marine organisms and represent a new habitat in the studied coast. The taxonomic profile of the communities supported by marine litter and hard natural substrate were significantly different. Moreover, opposite to the expectations of reduced diversity in artificial structures, more diverse communities were found on litter. Non-indigenous species were attached mainly to non-plastic artificial materials. From these results it can be concluded that marine litter can significantly alter the biotic composition of coastal ecosystem, representing a shelter for invasive species and diverse natives.
Understanding how invasive species affect key ecological interactions and ecosystem processes is imperative for the management of invasions. We evaluated the effects of invasive corals (Tubastraea spp.) on fish trophic interactions in an Atlantic coral reef. Remote underwater video cameras were used to examine fish foraging activity (bite rates and food preferences) on invasive cover levels. Using a model selection approach, we found that fish feeding rates declined with increased invasive cover. For Roving Herbivores (RH) and Sessile Invertivores (SI), an abrupt reduction of fish feeding rates corresponded with higher invasive cover, while feeding rates of Territorial Herbivores (TH) and Mobile Invertivores (MI) decreased linearly with cover increase. Additionally, some fish trophic groups, such as RH, SI and Omnivores (OM), had lower densities in reef sections with high invasive cover. These findings demonstrate that invasive corals negatively impact fish-benthic interactions, and could potentially alter existing trophic relationships in reef ecosystems.
Despite the devastating impact of the lionfish (Pterois volitans) invasion on NW Atlantic ecosystems, little genetic information about the invasion process is available. We applied Genotyping by Sequencing techniques to identify 1,220 single nucleotide polymorphic sites (SNPs) from 162 lionfish samples collected between 2013 and 2015 from two areas chronologically identified as the first and last invaded areas in US waters: the east coast of Florida and the Gulf of Mexico. We used population genomic analyses, including phylogenetic reconstruction, Bayesian clustering, genetic distances, Discriminant Analyses of Principal Components, and coalescence simulations for detection of outlier SNPs, to understand genetic trends relevant to the lionfish’s long-term persistence. We found no significant differences in genetic structure or diversity between the two areas (FSTp-values > 0.01, and t-test p-values > 0.05). In fact, our genomic analyses showed genetic homogeneity, with enough gene flow between the east coast of Florida and Gulf of Mexico to erase previous signals of genetic divergence detected between these areas, secondary spreading, and bottlenecks in the Gulf of Mexico. These findings suggest rapid genetic changes over space and time during the invasion, resulting in one panmictic population with no signs of divergence between areas due to local adaptation.
Ship’s ballast water has been a vector for the spreading of nonindigenous invasive species (NIS) around the globe for more than a century and has had devastating impact on aquatic ecosystems in many regions. Due to the harsh climate, shipping activities in Arctic waters have been limited compared to many parts of the world but will increase in the coming years due to climate changes. This will potentially affect the pristine Arctic marine ecosystems by introduction of NIS. In this chapter, we present the international ballast water regulations that have entered into force and the specific challenges of ballast water management in relation to the Arctic environment and marine ecosystems. We discuss the risk of NIS affecting the Arctic marine ecosystems including the impact of increased shipping activity, changes in living conditions of marine organisms because of climate changes and lack of knowledge of the eco-physiological boundaries and distributions of Arctic marine species. It is concluded that at present only a few marine NIS have been recorded in the Arctic area. Despite the existing and planned ballast water regulations, NIS establishment in the region will increase with an unknown magnitude due to lack of biological data.