Invasive species

Native Predators Do Not Influence Invasion Success of Pacific Lionfish on Caribbean Reefs

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. 

Date
2013
Data type
Scientific article
Theme
Research and monitoring
Journal

Extirpation of the Snowy Plover (Charadrius alexandrinus) on St. Martin, West Indies

Abstract:

Recent surveys for the Snowy Plover (Charadrius alexandrinus) on St. Martin reveal that the species is no longer a resident on the island. Following surveys from 1997–2005, when the species was annually detected and observed breeding, plovers were no longer observed on the island. Both human disturbance to nesting birds and predation by invasive species are potential causes of the extirpation. 

Date
2012
Data type
Scientific article
Theme
Research and monitoring
Geographic location
St. Maarten
Author

Linking removal targets to the ecological effects of invaders: a predictive model and field test

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.

Date
2014
Data type
Scientific article
Theme
Research and monitoring

Effectiveness of lionfish removal efforts in the southern Caribbean

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. 

Date
2013
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Bonaire
Curacao

Misleading criticisms of invasion science: a field guide

Invasion science is the study of the causes and consequences of the introduction of organisms to the areas outside their native ranges. It concerns all aspects relating to the transport, establishment and spread of organisms in a new target region, their interactions with resident organisms, and the costs and benefits of invasion with reference to human value systems. ‘Invasion science’ is a more appropriate name for the broad domain than ‘invasion ecology’ or ‘invasion biology’ because of the importance of engaging with many disciplines other than biology and ecology in understanding and managing invasions...

Date
2013
Data type
Scientific article
Theme
Research and monitoring

On the relationship between native grouper and invasive lionfish in the Caribbean

Abstract:

The Indo-Pacific lionfish, Pterois volitans, has invaded most of the Tropical Western Atlantic in the last few years. The degree to which populations of this invasive species can be controlled by native predatory fish (mostly grouper), is controversial with conflicting reports. Here, we review the evidence of two recent papers and point out some of the difficulties in inferring predator-limitation purely from observational data. A negative relationship has been found between large-bodied grouper and lionfish during early colonisation though the degree to which this is caused by direct predation versus behavioural mechanisms is unclear. Evidence to the contrary from a recent study suffers confounding effects of habitat quality, fishing, and dispersal and therefore remains equivocal. 

Date
2013
Data type
Scientific article
Theme
Research and monitoring
Journal
Author