The detrimental effects of invasive lionfishes (Pterois volitans and Pterois miles) on western Atlantic shallow reefs are well documented, including declines in coral cover and native fish populations, with disproportionate predation on critically endangered reef fish in some locations. Yet despite individuals reaching depths >100 m, the role of mesophotic coral ecosystems (MCEs; reefs 30–150 m) in lionfish ecology has not been addressed. With lionfish control programs in most invaded locations limited to 30 m by diving restrictions, understanding the role of MCEs in lionfish distributions remains a critical knowledge gap potentially hindering conservation management. Here we synthesise unpublished and previously published studies of lionfish abundance and body length at paired shallow reef (0–30 m) and MCE sites in 63 locations in seven western Atlantic countries and eight sites in three Indo-Pacific countries where lionfish are native. Lionfish were found at similar abundances across the depth gradient from shallow to adjacent MCEs, with no difference between invaded and native sites. Of the five invaded countries where length data were available three had larger lionfish on mesophotic than shallow reefs, one showed no significant difference, while the fifth represented a recently invaded site. This suggests at least some mesophotic populations may represent extensions of natural ontogenetic migrations. Interestingly, despite their shallow focus, in many cases culling programs did not appear to alter abundance between depths. In general, we identify widespread invasive lionfish populations on MCE that could be responsible for maintaining high densities of lionfish recruits despite local shallow-biased control programs. This study highlights the need for management plans to incorporate lionfish populations below the depth limit of recreational diving in order to address all aspects of the local population and maximise the effectiveness of control efforts.
While sustained removals of lionfish in shallow water can limit the impacts of these invasive species in certain locations, devices conceived for deep water control have not yet proven effective. Two new trap designs are presented that can target lionfish in deep water and reduce negative effects on native species that are ecologically, recreationally, or commercially important. The traps may also support efforts to meet the increasing demand for lionfish in the seafood market. The proposed designs have structural components that provide vertical relief to attract lionfish, and low profile frames that remain open during deployment. They have several benefits over conventional fish traps, including high attraction rates for lionfish, limited or no by-catch, no mortality from containment during the soak period, no bait to attract non-targeted species, no potential for ghost fishing, and easy portability on a fishing vessel.
Biological invasions are major contributors to global change and native biodiversity decline. However, they are overlooked in marine conservation plans. Here, we examine for the first time the extent to which marine conservation planning research has addressed (or ignored) biological invasions. Furthermore, we explore the change of spatial priorities in conservation plans when different approaches are used to incorporate the presence and impacts of invasive species.
Global analysis with a focus on the Mediterranean Sea region.
We conducted a systematic literature review consisting of three steps: (1) article selection using a search engine, (2) abstract screening and (3) review of pertinent articles, which were identified in the second step. The information extracted included the scale and geographical location of each case study as well as the approach followed regarding invasive species. We also applied the software Marxan to produce and compare conservation plans for the Mediterranean Sea that either protect, or avoid areas impacted by invasives, or ignore the issue. One case study focused on the protection of critical habitats, and the other on endemic fish species.
We found that of 119 papers on marine spatial plans in specific biogeographic regions, only three (2.5%) explicitly took into account invasive species. When comparing the different conservation plans for each case study, we found that the majority of selected sites for protection (ca. 80%) changed in the critical habitat case study, while this proportion was lower but substantial (27%) in the endemic fish species case study.
Biological invasions are being widely disregarded when planning for conservation in the marine environment across local to global scales. More explicit consideration of biological invasions can significantly alter spatial conservation priorities. Future conservation plans should explicitly account for biological invasions to optimize the selection of marine protected areas.
We assessed how establishment patterns of non-native freshwater, marine and terrestrial species into Northwest Europe (using Great Britain, France, Belgium and the Netherlands as the study countries) have changed over time, and identified the prevalent pathways and vectors of recent arrivals. Data were extracted from 33 sources on (a) presence/absence and (b) first year of observation in the wild in each country, and (c) continent(s) of origin, (d) invasion pathway(s), (e) invasion vector(s) and (f) environment(s) for 359 species, comprising all non-native Mollusca, Osteichthyes (bony fish), Anseriformes (wildfowl) and Mammalia, and non-native invasive Angiospermae present in the area. Molluscs, fish and wildfowl, particularly those originating from South America, arrived more recently into Northwest Europe than other groups, particularly mammals, invasive plants and species originating from North America. Non-deliberate introductions, those of aquatic species and those from elsewhere in Europe and/or Asia increased strongly in importance after the year 2000 and were responsible for 69, 83 and 89 % of new introductions between 2001 and 2015, respectively. Non-deliberate introductions and those from Asia and North America contributed significantly more to introductions of invasive species in comparison to other non-native species. From the 1960s, ornamental trade has increased in importance relative to other vectors and was responsible for all deliberate introductions of study groups since 2001. Non-deliberate introductions of freshwater and marine species originating from Southeast Europe and Asia represent an increasingly important ecological and economic threat to Northwest Europe. Invertebrates such as molluscs may be particularly dangerous due to their small size and difficulties in detection. Prevention of future invasions in this respect will require intensive screening of stowaways on boats and raising of public awareness.
Non-trophic interactions between Indo-Pacific lionfish Pterois volitans and P. miles and Atlantic and Caribbean reef fishes are not yet well understood. To determine the effects of potential competitive and behavioral interactions between native predators and invasive lionfish, we experimentally altered the presence of lionfish and red grouper Epinephelus morio in karst solution holes in Florida Bay, USA, and then tracked subsequent changes in the juvenile reef fish and motile macroinvertebrate communities for 6 wk. Relative to solution holes where we excluded both predators, mean juvenile reef fish abundance declined 83.7% in solution holes with a lionfish but increased by 154% in solution holes with a red grouper. There was no difference in juvenile reef fish abundance in solution holes with both lionfish and red grouper compared to holes where we excluded both predators. The composition of lionfish stomach contents shifted from mostly teleost fishes when lionfish were present in solution holes alone, to mostly crustaceans when in the presence of a red grouper. Concurrently, the abundance of 2 species of cleaner shrimp (Ancylomenes pedersoni and Periclimenes yucatanicus) decreased by 14.7% when lionfish were present but increased by 56.2% at holes where lionfish were excluded. We suggest that these results are due to altered lionfish predatory behavior in the presence of red grouper and highlight the importance of maintaining intact native predator communities for ameliorating the negative effects of the lionfish invasion.
Mediterranean marine biodiversity is undergoing a tropicalization process. We present the first record and spread dynamics of the tropical green seaweed Halimeda incrassata (Bryopsidales, Chlorophyta) from the Mediterranean Sea. Plants were observed at 2 sites off Mallorca island (NW Mediterranean), and species identification was confirmed molecularly. Since the first observation of this alien seaweed in 2011, it has spread rapidly in the shallow subtidal habitat of a marine protected area located in Palma Bay, which has a depth of up to ca. 20 m. By 2015, this species spread by a factor of 6.75 and extended to an area of 2.7 km2, covering a total of 41% of the monitored area. The dynamics of the invasion suggest rapid colonization and establishment and spreading of the species through shallow sedimentary and rocky habitats. H. incrassata has the potential to strongly alter the ecosystem services and functioning of shallow Mediterranean habitats. We encourage authorities to pay attention to the spread of this alien seaweed at larger scales and determine the positive and negative effects of the invasion in order to facilitate research-driven decision making.
Non-indigenous species (NIS) can have adverse environmental, economic and social impacts. Their management is now incorporated into key legislation, including the European Union (EU) Marine Strategy Framework Directive and the EU Regulation on the prevention and management of the introduction and spread of invasive alien species. Prevention of NIS introductions and the early detection of NIS following their introduction are recognised as the most effective approaches for reducing the potential impacts of NIS. This is true for most aquatic environments but especially so for the marine environment, where control and/or eradication are often not achievable. By assessing introduction vector activity, it is possible to identify coastal areas and specific locations where marine NIS may be more likely to be introduced. This study uses data relating to the activity of key introduction vectors; shipping, recreational boating and live animal aquaculture import, to estimate the relative risk of introduction of NIS around coastal regions of Great Britain and Ireland. Spatial analysis was used to create “heat” maps indicating coastal areas of increased relative risk of introduction of NIS by these vectors. The results of the present study will be crucial for the implementation of targeted vector management plans, supporting preventive strategies, and will facilitate a risk analyses of NIS threats to inform monitoring and surveillance programmes.
Understanding the drivers and barriers to participation in citizen science initiatives for conservation is important if long-term involvement from volunteers is expected. This study investigates the motivations of individuals from five marine protected areas (MPAs) in the Dutch Caribbean to (not) participate in different initiatives around lionfish. Following an interpretive approach, semi-structured interviews with seventy-eight informants were conducted and analyzed using thematic network analysis. Approximately 60% (n = 48) of informants indicated that they had participated in citizen science initiatives at the outset of the invasion. From this group, almost half said that they still participated in some type of data collection, but only a few did so within a citizen science context. Many informants were initially motivated to participate in lionfish detection and response initiatives due to concern for the environment. Personal meanings attached to both the data collection experiences and to the data influenced informants’ motivations to sustain or cease data collection and/or sharing. In time, the view of lionfish as a threat changed for many informants as this species’ recreational and/or commercial value increased. Enabling and constraining factors for data collection and sharing were identified at the personal, interpersonal, organizational and technical levels. Our findings have implications for the design of future citizen science initiatives focused on invasive species.
Restoration of native species may be hampered by competition with non-native species. The outcomes of competition are often context-dependent, with one species dominating under some conditions but not others. Where non-natives differ from natives in their ability to tolerate stressful environmental conditions, restoration practitioners may be able to manipulate conditions or strategically locate restoration projects along naturally occurring stress gradients to favor native species. We tested the responses of native oysters and a suite of non-native sessile invertebrate species (mostly soft-bodied organisms) to varying tidal elevations, shoreline types, and distances from source populations. Cover of non-natives was lower at higher tidal elevation and far from adult populations. Native oyster recruitment was also reduced at the high tidal elevation. At this elevation oyster dominance was increased, but abundance was reduced. To test an adaptive management approach, we moved substrates from the low to high tidal elevations. Cover of non-natives had decreased dramatically one year later, while oyster metrics were unaffected or improved compared to those on substrates remaining at the low elevation. Our study indicates that reduction of non-native species abundance, often an explicit goal of restoration, may be achieved by strategic location of restoration units, although abundance of target species may also be reduced, at least over the short term. However, restoration practitioners may be able to increase abundance of target species and reduce non-natives by applying stress differentially over time, with benign conditions during sensitive early life stages, and increasing stress after target organisms become more tolerant.
Marine biological invasions threaten biodiversity worldwide. Here we explore how Marine Protected areas, by reducing human use of the coast, confer resilience against the introduction of non-indigenous species (NIS), using two very different Pacific islands as case studies for developing and testing mathematical models. We quantified NIS vectors and promoters on Vancouver (Canada) and Moorea (French Polynesia) islands, sampled and barcoded NIS, and tested models at different spatial scales with different types of interaction among vectors and between marine protection and NIS frequency. In our results NIS were negatively correlated with the dimension of the protected areas and the intensity of the protection. Small to medium geographical scale protection seemed to be efficient against NIS introductions. The likely benefit of MPAs was by exclusion of aquaculture, principally in Canada. These results emphasize the importance of marine protected areas for biodiversity conservation, and suggest that small or medium protected zones would confer efficient protection against NIS introduction.