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Invasive lionfish (Pterois volitans/miles) pose a serious threat to marine ecosystems throughout the western Atlantic Ocean and Caribbean Sea. The development of a fishery for lionfish has been proposed as a strategy for controlling populations; however, there is concern about consumption of this species by humans due to its high trophic position and potential for bioaccumulation of mercury. We analyzed total mercury (THg) in tissues of lionfish from two locations on the east coast of Florida. THg in lionfish increased with size and differed by location and sex. THg was highest in muscle tissue and was strongly positively correlated among tissues. THg in lionfish was lower than other commonly consumed marine fishes, and falls into Florida's least restrictive advisory level. Consumption of lionfish poses a low risk and concerns over mercury bioaccumulation should not present a significant barrier to lionfish harvest.

Substantial declines in reef fishes were observed at northern Gulf of Mexico artificial reef sites between 2009–2010 and 2011–2012, a period that bracketed the appearance of invasive lionfish in this ecosystem. Small demersal reef fishes, the predominant prey of lionfish in other systems, displayed the greatest declines. However, a confounding factor during this time was the Deepwater Horizon Oil Spill (DWH) in summer 2010. In some areas, targeted lionfish removals have been demonstrated to mitigate negative effects on native fishes. Therefore, we conducted a 2 yr experiment to examine the effectiveness and ecological benefits of targeted lionfish removals at artificial reefs (n = 27) off northwest Florida, USA, where lionfish densities reached the highest recorded in the western Atlantic by 2013. All lionfish were removed via spearfishing from 17 reefs in December 2013, 9 of which were periodically re-cleared of lionfish through May 2015. Remaining sites served as uncleared controls. Both juvenile and adult lionfish quickly recruited to cleared reefs, with lionfish reaching pre-clearance densities in <1 yr on reefs cleared only once. Removal treatment significantly affected reef fish community structure at experimental reefs, but removal effort was insufficient to achieve substantial gains for most taxa, and declines in several taxa were observed throughout, regardless of treatment. It is unclear whether chronic effects of the DWH or regionally high lionfish densities were more important factors in explaining trends observed in reef fish communities, but small-scale targeted lionfish removal efforts had few positive impacts overall on native reef fish communities in this study.

As a generalist and opportunistic predator, lionfish (Pterois volitans and P. miles) consume large quantities of juvenile reef fish and invertebrates, as well as the adults of small-bodied species. To better understand the impacts of these fishes upon invaded coral reef ecosystems, we describe the feeding habits of invasive lionfish in Bermuda based on stomach contents analysis, and the influence that environmental factors have on their diet via spatial and temporal changes in prey availability. Relative to other regions throughout the northwestern Atlantic, lionfish in Bermuda consume a greater proportion of crustaceans, and their diet appears to rely upon the relative abundance of available prey species. A poorly -known crustacean, the red night shrimp Cinetorhynchus rigens, is the species of greatest importance to the diet of Bermuda lionfish. Currently, herbivorous fishes do not make a major contribution to their diet, although the lionfish frequently target both ecologically (e.g. bluehead wrasse Thalassoma bifasciatum) and economically important species (e.g. Atlantic creolefish Paranthias furcifer).

Atlantic lionfish have caused measurable ecosystem damage in their invaded range. As a matter of urgency, strategies to suppress lionfish have therefore risen to the fore amongst the ocean management community. We use a biophysical model and ocean climate data to demonstrate how Atlantic lionfish larvae are dispersed by currents and how this dispersal, combined with their breeding strategy, negates effective control using methods traditionally executed on a local scale. This study quantitatively emphasizes the high level of larval connectivity that exists between the many nations whose waters now support established lionfish populations. For any given area, our results indicate that the key to suppressing the invasion is to simultaneously choke all upstream linkages that supply external larvae and renourish the local population. On the basis of a case study developed for the Carolinas, USA, an area of high lionfish abundance, the model suggests that such a strategy requires monthly culls that remove 20% of lionfish biomass in the Carolinas and all locations to which the Carolinas are linked hydrographically. Conversely, if culls target only those locales that deliver the majority (95%) of lionfish larvae to the Carolinas, and therefore ignore those locations which contribute the remaining 5% of lionfish larvae, the requisite cull rate exceeds 60% and suppresses lionfish abundance for only 5 yr. The latter finding exposes an intrinsic danger: sparse lionfish left uncontrolled may derail a concerted, yet not comprehensive, effort to control the invader. This study provides a modelling approach to quantitatively target and manage the lionfish population for nations whose waters are now plagued by invasive lionfish.

The invasion of the western Atlantic by the Indo-Pacific lionfish (Pterois volitans/miles) is a serious threat to the ecological stability of the region. The early life history of the lionfish remains poorly understood despite the important role that larval supply plays reef fish population dynamics. In this study, we characterized patterns in the horizontal and vertical distributions of larval lionfish collected in the western Caribbean, US Caribbean, and the Gulf of Mexico from 19 ichthyoplankton surveys conducted from 2009-2016. Using generalized additive models (GAMs), we assessed the relative effects of spatiotemporal and environmental variation on the distribution of lionfish larvae. We also examined otoliths to determine larval ages and report the first larval growth rate estimates for this species. Lionfish larvae were present at 7.8% of all stations sampled and our model suggests that lionfish presence is related to sea surface temperature and the lunar cycle. Year and location also strongly affected the larval distribution, likely reflecting the ongoing expansion of the species during our sampling timeframe. Much of the variation in larval lionfish presence remained unexplained, and future studies should incorporate additional environmental factors to improve model predictions. This study improves our understanding of the lionfish life cycle and accentuates the need for further research into the early life history of this invasive species. The design and implementation of effective long-term lionfish control mechanisms will require an understanding of their entire life history.

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.

Sound is a valuable cue in the marine environment that can inform animals about habitat location and community composition. Indeed, sound is often used for orientation and navigation by larval reef fishes during settlement. However, despite sound’s role in the early life of reef fishes, whether post-settlement reef fishes use ambient soundscapes to inform their movement decisions remains less clear. In an in-situ playback experiment in Curaçao, the Dutch Caribbean, settled individuals of an invasive predator, the Indo-Pacific lionfish ( Pterois volitans ), showed no preference to move towards the playbacks of two different habitat types during daylight hours. In particular, lionfish did not prefer to move towards the sounds of sandy or reef habitat playbacks when tested against a silent control. Moreover, when given a choice between simultaneous sandy and reef habitat playbacks, lionfish showed no preference for the soundscape of either habitat type. While the activity of lionfish was strongly correlated with their body size, with larger fish being more active, activity was not affected by habitat playback, nor did body size affect their preference for the soundscapes of either habitat type. While acoustic lures have been speculated to be a promising addition to existing lionfish trap designs, daytime playbacks of ambient soundscapes are unlikely to be successful in attracting lionfish post-settlement, ultimately affecting their efficacy.

Fish support microbial communities that serve a variety of functions, including disease resistance. In addition to fish microbiota acting as a defense against disease, fish mucus often contains antimicrobial compounds. This study investigated the antibacterial activity of bacteria isolated from external surfaces of native (e.g. Indo-Pacific) and invasive (e.g. Western Atlantic, Caribbean) lionfish (Pterois volitans/miles complex) and native Caribbean squirrelfish Holocentrus adscensionis against 6 known fish pathogens (Vibrio spp., Photobacterium damselae), and evaluated the antibacterial activity of lionfish mucus against these pathogens and lionfish and squirrelfish-associated bacteria. The 16S rRNA gene was sequenced for bacteria exhibiting pathogen inhibition, providing information on their taxonomic affiliations. Antibacterial metabolites were produced by 36.2% (54 of 149) of lionfish-derived bacterial cultures, with similar percentages of producing organisms recovered from the native and invaded ranges. Only 1 of 13 squirrelfish isolates inhibited pathogens. Interestingly, similar genera exhibiting antibacterial activity were detected in both ranges (e.g. Alteromonas, Pseudoalteromonas, Photobacterium), even though previous work suggested that external bacterial communities were not vertically transmitted. Antibacterial activity was detected after 24 h of growth, and the amount of inhibition did not increase over a 14 d incubation period. Conversely, organic and aqueous mucus extracts from lionfish were not active against the 6 pathogens or against bacteria isolated from lionfish and squirrelfish. These findings indicate that the external bacterial communities of lionfish may provide disease resistance to their hosts, a trait that would enhance the ability of lionfish to successfully establish as an invasive species.