Lionfish

Understanding predator-prey relationships gives greater insight into coral reef health. A recent study on predator-prey relationships linked the relative brain mass of predators and their prey. Predation pressure forces prey to use decision making skills that require higher cognition by inspecting and identifying predators and then adjusting their behavior to achieve the highest chance for survival. However, the predation pressure that prey face outweighs the pressure predators face to find a prey. This results in prey having larger relative brain masses than their predators. There is little data on relative brain mass of fishes with few natural predators such as Pterois volitans. This study compared the brain mass to body mass ratio of P. volitans, which have very few natural predators and thus very little predation pressure, to the brain mass to body mass ratio of their prey, possible predators, competitors, and taxonomically similar fish. This study also analyzed the response of lionfish to divers with nets in order to investigate their ability to recognize divers as predators. Lionfish did swim away from divers 56.5% of the time which indicates that lionfish might be able to recognize divers as predators. Lionfish had a significantly smaller relative brain mass than their predators, prey, and competitors, but was not significantly smaller than taxonomically similar fish. These results demonstrate that the morphological antipredator adaptation of venomous spines cause very little predation pressure. Thus, lionfish are not forced to use the same cognitive skills as other prey or predators and in turn have smaller relative brain masses.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 10-20 from CIEE Bonaire.

Lionfish impacts are highly negative (directly or indirectly) on native populations and the entire Caribbean ecosystem.Since December 2010, when the first lionfish was sighted, STENAPA marine park staffs are actively culling lionfish at different dive sites in and out of both marine reserves
Does the culling program significantly reduce the lionfish population in St Eustatius? The aims of this question are: (i) to prove the efficiency of the removal effort, while describing any evolution of the lionfish population, (ii) to bring out the site where it is necessary to focus the culling program, (iii) to make recommendations to improve the efficiency of the current culling program.
What can we learn with the culling program data about the lionfish and its behavior? This second part aims to learn more about the lionfish on Statia and to compare the results with other data due to (i) the identification of the diet composition and feeding behavior of the lionfish by analyzing their stomach content and (ii) the determination of the size distribution of the lionfish on Statia.

The red lionfish (Pterois volitans) is an invasive predatory marine fish that has rapidly expanded its pres- ence in the Western Hemisphere. We collected 214 invasive red lionfish samples from nine countries and territories, including seven unpublished locations. To more compre- hensively evaluate connectivity, we compiled our d-loop sequence data with 846 published sequences, resulting in 1,060 samples from 14 locations. We found low nucleo- tide diversity (π = 0.003) and moderate haplotype diversity (h = 0.59). Using haplotype population pairwise ΦST tests, we analyzed possible phylogeographic breaks that were pre- viously proposed based on other reef organisms. We found support for the Bahamas/Turks/Caicos versus Caribbean break (ΦST = 0.12) but not for the Northwestern Carib- bean, Eastern Caribbean, or US East Coast versus Bahamas breaks. The Northern Region had higher variation and more haplotypes, supporting introductions of at least five haplo- types to the region. Our wide-ranging samples showed that a lower-frequency haplotype in the Northern Region domi- nated the Southern Region and suggested multiple introduc- tions, possibly to the south. We tested multiple scenarios of phylogeographic structure with analyses of molecular vari- ance and found support for a Northern and Southern Region split at the Bahamas/Turks/Caicos versus Caribbean break (percentage of variation among regions = 8.49 %). We found that Puerto Rico clustered with the Southern Region more strongly than with the Northern Region, as opposed to previous reports. We also found the rare haplotype H03 for the first time in the southern Caribbean (Panama), indicat- ing that either secondary releases occurred or that the low- frequency haplotypes have had time to disperse to extreme southern Caribbean locations. 

Summary:

Lionfishes are venomous species of scorpionfishes which are native to Indo-Pacific coral reef ecosystems and adjacent habitats. Because of their colorful and dramatic appearance, they are prized by aquarists around the world. Through accidental and/or purposeful release into warm Atlantic waters, they have become established as a highly problematic alien species that poses a serious threat to coral reefs in Bermuda, Florida, the Gulf of Mexico, the Caribbean islands, Central America, and northern South America. Invasive lionfish populations can reach high densities and cause extreme disruption to native fish communities; they have been shown to reduce biodiversity, are responsible for the decline of ecologically important species, and hinder stock-rebuilding efforts for economically important species.

In January 2010, in recognition of the severity of the lionfish invasion and its impact on coral reefs and local communities, the 24th General Meeting of the International Coral Reef Initiative (ICRI) agreed to set up an Ad Hoc Committee to develop a strategic plan for the control of lionfish in the Wider Caribbean. The Strategy described in this document is one of the actions implemented by the Ad Hoc Committee, known as the Regional Lionfish Committee (RLC). It seeks to build on the existing programs and efforts aimed at minimizing the impacts of the lionfish in the region, and to provide a framework for action to provide a regionally coordinated response to the lionfish threat. The Strategy is based on the following objectives:

1. i)  Facilitate collaboration among governments, reef-reliant industries, civil society, and academia by providing mechanisms for coordination of efforts across political and geographical boundaries,
2. ii)  Encourage a coordinated research and monitoring agenda,
3. iii)  Encourage governments to review and amend relevant legislation and, if necessary, develop new regulations and policies to control lionfish,
4. iv)  Control invasive lionfish populations using regionally coordinated, effective methods, and
5. v)  Provide education, information and outreach mechanisms to generate public support and foster stewardship in invasive lionfish programs.

Each of the objectives is supported by strategies and actions with specific stakeholders identified as possible implementers. It is expected that this Strategy will be used by governments and other stakeholders to create plans to implement many of the actions identified in this strategy. The action plans would include timelines and indicators to measure effectiveness in achieving the objectives of this Strategy. Local government, coastal communities, non-governmental organizations (NGOs), and marine industries will play an important role in implementing on-ground actions to reduce lionfish impacts and enhance the resilience of reefs in the Wider Caribbean region. 

Abstract:

As a result of being hunted, animals often alter their behaviour in ways that make future encounters with predators less likely. When hunting is carried out for conservation, for example to control invasive species, these behavioural changes can inadvertently impede the success of future efforts. We examined the effects of repeated culling by spearing on the behaviour of invasive predatory lionfish (Pterois volitans/miles) on Bahamian coral reef patches. We compared the extent of concealment and activity levels of lionfish at dawn and midday on 16 coral reef patches off Eleuthera, The Bahamas. Eight of the patches had been subjected to regular daytime removals of lionfish by spearing for two years. We also estimated the distance at which lionfish became alert to slowly approaching divers on culled and unculled reef patches. Lionfish on culled reefs were less active and hid deeper within the reef during the day than lionfish on patches where no culling had occurred. There were no differences at dawn when removals do not take place. Lionfish on culled reefs also adopted an alert posture at a greater distance from divers than lionfish on unculled reefs. More crepuscular activity likely leads to greater encounter rates by lionfish with more native fish species because the abundance of reef fish outside of shelters typically peaks at dawn and dusk. Hiding deeper within the reef could also make remaining lionfish less likely to be encountered and more difficult to catch by spearfishers during culling efforts. Shifts in the behaviour of hunted invasive animals might be common and they have implications both for the impact of invasive species and for the design and success of invasive control programs. 

This month’s issue profiles several scientific discoveries with new implications for conservation in the Dutch Caribbean. On St. Eustatius, the first evidence of a rat stealing a seabird egg from a nest was captured with the use of camera traps – a component of STENAPA’s Red-billed Tropicbird conservation work. On Curaçao, a research team from Naturalis Biodiversity Center in the Netherlands carried out dedicated surveys on crabs, shrimps and molluscs living in association with corals and other invertebrate hosts. The study yields several new species records for Curaçao, new symbiotic associations and possibly even species new to science.

Caribbean-wide, lionfish removal efforts have been a major component of conservation action in regards to this invasive predator. New evidence suggests this could be a permanent, but successful solution in controlling and limiting the impacts of the Lionfish. Additionally, the lionfish control website (www. lionfishcontrol.org), originally set up by STINAPA Bonaire and DCNA to support and monitor lionfish control efforts has been expanded to include Aruba, Curaçao and St. Maarten.

Content:

• ‘Breaking News’: Rats confirmed stealing eggs on St. Eustatius!
• New Biodiversity Records for Curaçao
• Lionfish Control Efforts Show Success
• Overview of Research and Monitoring Efforts
• Calendar of Upcoming Events, Meetings and Workshops

This month’s issue focuses on the Audubon’s Shearwater. Despite its resounding and unique call, this threatened bird often goes unnoticed on our islands, coming to shore at night to nest in remote locations. On Saba and St. Eustatius efforts are underway to confirm the presence of breeding shearwaters and locate their nests utilising predictive GIS modelling.

In the surrounding waters of the ABC islands an aerial survey took place last month to monitor the presence, density and distribution of marine mammals. An observation team from IMARES covered almost the entire Exclusive Economic Zone (EEZ) of the three islands, recording a number of marine mammal species as well as other megafauna.

Other content:

• ‘Breaking News’: Lionfish Control Efforts are Working on Bonaire and Curaçao!
• ‘Research of the Month‘: Aerial Marine Mammal Survey Around The Leeward Islands
• Audubon’s Shearwater: “Things That Go Bump In The Night”
• Overview of Research and Monitoring Efforts
• Calendar of Upcoming Events, Meetings and Workshops

Abstract:

Biotic resistance, the process by which new colonists are excluded from a community by predation from and/or competition with resident species, can prevent or limit species invasions. We examined whether biotic resistance by native predators on Caribbean coral reefs has influenced the invasion success of red lionfishes (Pterois volitans and Pterois miles), piscivores from the Indo-Pacific. Specifically, we surveyed the abundance (density and biomass) of lionfish and native predatory fishes that could interact with lionfish (either through predation or competition) on 71 reefs in three biogeographic regions of the Caribbean. We recorded protection status of the reefs, and abiotic variables including depth, habitat type, and wind/wave exposure at each site. We found no relationship between the density or biomass of lionfish and that of native predators. However, lionfish densities were significantly lower on windward sites, potentially because of habitat preferences, and in marine protected areas, most likely because of ongoing removal efforts by reserve managers. Our results suggest that interactions with native predators do not influence the colonization or post-establishment population density of invasive lionfish on Caribbean reefs. 

Abstract:

Species invasions have a range of negative effects on recipient ecosystems, and many occur at a scale and magnitude that preclude complete eradication. When complete extirpation is unlikely with available management resources, an effective strategy may be to suppress invasive populations below levels predicted to cause undesirable ecological change. We illustrate this approach by developing and testing targets for the control of invasive Indo-Pacific lionfish (Pterois volitans and P. miles) on Western Atlantic coral reefs. We first developed a size-structured simulation model of predation by lionfish on native fish communities, which we used to predict threshold densities of lionfish beyond which native fish biomass should decline. We then tested our predictions by experimentally manipulating lionfish densities above or below reef-specific thresholds, and monitoring the consequences for native fish populations on 24 Bahamian patch reefs over 18 months. We found that reducing lionfish below predicted threshold densities effectively protected native fish community biomass from predation-induced declines. Reductions in density of 75- 95%, depending on the reef, were required to suppress lionfish below levels predicted to over-consume prey. On reefs where lionfish were kept below threshold densities, native prey fish biomass increased by 50-70%. Gains in small (<6cm) size classes of native fishes translated into lagged increases in larger size classes over time. The biomass of larger individuals (>15cm total length), including ecologically important grazers and economically important fisheries species, had increased by 10-65% by the end of the experiment. 

Crucially, similar gains in prey fish biomass were realized on reefs subjected to partial and full removal of lionfish, but partial removals took 30% less time to implement. By contrast, the biomass of small native fishes declined by more than 50% on all reefs with lionfish densities exceeding reef-specific thresholds. Large inter-reef variation in the biomass of prey fishes at the outset of the study, which influences the threshold density of lionfish, means that we could not identify a single rule-of-thumb for guiding control efforts. However, our model provides a method for setting reef-specific targets for population control using local monitoring data. Our work is the first to demonstrate that for ongoing invasions, suppressing invaders below densities that cause environmental harm can have a similar effect, in terms of protecting the native ecosystem on a local scale, to achieving complete eradication.

Abstract:

Lionfish (Pterois volitans and P. miles) have spread rapidly throughout the Caribbean Sea since 1985, where they negatively impact native fish communities and therefore are considered by some as the most damaging invasive species in the Caribbean to date. To combat further population growth and spread of lionfish and to protect native fish communities, various Caribbean islands have started control efforts. On Bonaire, a removal program based on volunteers using spear guns was started immediately after the first lionfish was sighted in 2009, and a similar program was started on neighboring Curaçao 2 yr later. To determine the effectiveness of these removal efforts, differences in the density and biomass of lionfish were compared between areas in which lionfish were directly targeted during removal efforts (i.e. ‘fished’ areas) on Bonaire and areas where they were not (i.e. ‘unfished areas’) on both Bonaire and Curaçao. Lion- fish biomass in fished locations on Bonaire was 2.76-fold lower than in unfished areas on the same island and 4.14-fold lower than on unfished Curaçao. While removal efforts are effective at reducing the local number of lionfish, recruitment from unfished locations, such as those too deep for recreational diving and at dive sites that are difficult to access, will continuously offset the effects of removal efforts. Nevertheless, our results show that the immediate start and subsequent contin- uation of local removal efforts using volunteers is successful at significantly reducing the local density and biomass of invasive lionfish on small Caribbean islands.