RESUMO
Modelling the dynamics of small, interconnected populations, or metapopulations, can help pinpoint habitat patches that are critical for population persistence in patchy habitats. For conservation purposes, these patches are typically earmarked for protection, but for invasive species management, these patches could be targeted to hasten the populations' demise. Here, we show how metapopulation modelling, coupled with an understanding of size-dependent dispersal behaviour, can be used to help optimize the distribution of limited resources for culling specific populations of invasive Indo-Pacific lionfish (Pterois volitans) in the western Atlantic. Through simulation using fitted model parameters, we derive three insights that can inform management. First, culling lionfish from target patches reduces the probability of lionfish occupancy at surrounding patches. Second, this effect depends on patch size and connectivity, but is strongest at the local scale and decays with distance. Finally, size-dependent dispersal in lionfish means that size-selective culling can change both a population's size distribution and dispersal potential, with cascading effects on network connectivity, population dynamics and management outcomes. By explicitly considering seascape structure and movement behaviour when allocating effort to the management of invasive species, managers can optimize resource use to improve management outcomes. This article is part of the theme issue 'Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation'.
Assuntos
Conservação dos Recursos Naturais , Peixes , Espécies Introduzidas , Movimento , Animais , Bahamas , Meio Ambiente , Dinâmica PopulacionalRESUMO
The extent to which Marine Protected Areas (MPAs) benefit corals is contentious. On one hand, MPAs could enhance coral growth and survival through increases in herbivory within their borders; on the other, they are unlikely to prevent disturbances, such as terrestrial runoff, that originate outside their boundaries. We examined the effect of spatial protection and terrestrial sediment on the benthic composition of coral reefs in Saint Lucia. In 2011 (10 to 16 years after MPAs were created), we resurveyed 21 reefs that had been surveyed in 2001 and analyzed current benthic assemblages as well as changes in benthic cover over that decade in relation to protection status, terrestrial sediment influence (measured as the proportion of terrigenous material in reef-associated sediment) and depth. The cover of all benthic biotic components has changed significantly over the decade, including a decline in coral and increase in macroalgae. Protection status was not a significant predictor of either current benthic composition or changes in composition, but current cover and change in cover of several components were related to terrigenous content of sediment deposited recently. Sites with a higher proportion of terrigenous sediment had lower current coral cover, higher macroalgal cover and greater coral declines. Our results suggest that terrestrial sediment is an important factor in the recent degradation of coral reefs in Saint Lucia and that the current MPA network should be complemented by measures to reduce runoff from land.
Assuntos
Antozoários , Conservação dos Recursos Naturais , Recifes de Corais , Sedimentos Geológicos , Animais , Região do CaribeRESUMO
Understanding how predators select their prey can provide important insights into community structure and dynamics. However, the suite of prey species available to a predator is often spatially and temporally variable. As a result, species-specific selectivity data are of limited use for predicting novel predator-prey interactions because they are assemblage specific. We present a method for predicting diet selection that is applicable across prey assemblages, based on identifying general morphological and behavioural traits of prey that confer vulnerability to predation independent of species identity. We apply this trait-based approach to examining prey selection by Indo-Pacific lionfish (Pterois volitans and Pterois miles), invasive predators that prey upon species-rich reef fish communities and are rapidly spreading across the western Atlantic. We first generate hypotheses about morphological and behavioural traits recurring across fish species that could facilitate or deter predation by lionfish. Constructing generalized linear mixed-effects models that account for relatedness among prey taxa, we test whether these traits predict patterns of diet selection by lionfish within two independent data sets collected at different spatial scales: (i) in situ visual observations of prey consumption and availability for individual lionfish and (ii) comparisons of prey abundance in lionfish stomach contents to availability on invaded reefs at large. Both analyses reveal that a number of traits predicted to affect vulnerability to predation, including body size, body shape, position in the water column and aggregation behaviour, are important determinants of diet selection by lionfish. Small, shallow-bodied, solitary fishes found resting on or just above reefs are the most vulnerable. Fishes that exhibit parasite cleaning behaviour experience a significantly lower risk of predation than non-cleaning fishes, and fishes that are nocturnally active are at significantly greater risk. Together, vulnerable traits heighten the risk of predation by a factor of nearly 200. Our study reveals that a trait-based approach yields insights into predator-prey interactions that are robust across prey assemblages. Importantly, in situ observations of selection yield similar results to broadscale comparisons of prey use and availability, which are more typically gathered for predator species. A trait-based approach could therefore be of use across predator species and ecosystems to predict the outcomes of changing predator-prey interactions on community dynamics.
Assuntos
Peixes/anatomia & histologia , Peixes/fisiologia , Cadeia Alimentar , Atividade Motora , Comportamento Predatório , Animais , Bahamas , Recifes de Corais , Dieta , Espécies Introduzidas , Perciformes/fisiologiaRESUMO
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.
Assuntos
Espécies Introduzidas , Perciformes , Comportamento Predatório , Animais , Bahamas , Recifes de Corais , Ecossistema , Ilhas , OceanografiaRESUMO
Caribbean reefs have experienced unprecedented changes in the past 40 years. A major hypothesis to explain shifts in reef community composition relates to declining herbivory. This hypothesis was developed largely based on observations of Jamaican reefs from the 1980s onward, but it is widely held to be relevant regionally. We use a region-wide dataset on benthic composition to examine how well the pattern of ecological change on Jamaican reefs is mirrored by other Caribbean reefs. The extent to which macroalgal cover exceeds coral cover on Jamaican reefs is an order of magnitude more extreme than seen elsewhere. We suggest that Jamaican reefs are not representative of the degradation trajectory of Caribbean reefs and management based on the Jamaican experience may not be relevant elsewhere. However, the recovery of Jamaican reefs following the return of urchins gives us hope that Caribbean reefs are more resilient to catastrophic disturbances than previously thought.
Assuntos
Recifes de Corais , Ecologia/métodos , Conservação dos Recursos Naturais , Monitoramento Ambiental , JamaicaRESUMO
Indo-Pacific lionfish (Pterois volitans and P. miles) have spread swiftly across the Western Atlantic, producing a marine predator invasion of unparalleled speed and magnitude. There is growing concern that lionfish will affect the structure and function of invaded marine ecosystems, however detrimental impacts on natural communities have yet to be measured. Here we document the response of native fish communities to predation by lionfish populations on nine coral reefs off New Providence Island, Bahamas. We assessed lionfish diet through stomach contents analysis, and quantified changes in fish biomass through visual surveys of lionfish and native fishes at the sites over time. Lionfish abundance increased rapidly between 2004 and 2010, by which time lionfish comprised nearly 40% of the total predator biomass in the system. The increase in lionfish abundance coincided with a 65% decline in the biomass of the lionfish's 42 Atlantic prey fishes in just two years. Without prompt action to control increasing lionfish populations, similar effects across the region may have long-term negative implications for the structure of Atlantic marine communities, as well as the societies and economies that depend on them.
Assuntos
Peixes , Espécies Introduzidas , Comportamento Predatório , Animais , Bahamas , Biomassa , Recifes de Corais , Ecossistema , Oceanos e Mares , Dinâmica PopulacionalRESUMO
The architectural complexity of ecosystems can greatly influence their capacity to support biodiversity and deliver ecosystem services. Understanding the components underlying this complexity can aid the development of effective strategies for ecosystem conservation. Caribbean coral reefs support and protect millions of livelihoods, but recent anthropogenic change is shifting communities toward reefs dominated by stress-resistant coral species, which are often less architecturally complex. With the regionwide decline in reef fish abundance, it is becoming increasingly important to understand changes in coral reef community structure and function. We quantify the influence of coral composition, diversity, and morpho-functional traits on the architectural complexity of reefs across 91 sites at Cozumel, Mexico. Although reef architectural complexity increases with coral cover and species richness, it is highest on sites that are low in taxonomic evenness and dominated by morpho-functionally important, reef-building coral genera, particularly Montastraea. Sites with similar coral community composition also tend to occur on reefs with very similar architectural complexity, suggesting that reef structure tends to be determined by the same key species across sites. Our findings provide support for prioritizing and protecting particular reef types, especially those dominated by key reef-building corals, in order to enhance reef complexity.
Assuntos
Antozoários/classificação , Recifes de Corais , Animais , Índias OcidentaisRESUMO
User fees can contribute to the financial sustainability of marine protected areas (MPAs), yet they must be acceptable to users. We explore changes in the fee system and management of Bonaire National Marine Park (BNMP) from the perspective of users. Responses from 393 tourists indicated that 90% were satisfied with park conditions and considered current user fees reasonable. However, only 47% of divers and 40% of non-divers were prepared to pay more. Diver willingness-to-pay (WTP) appears to have decreased since 1991, but this difference could be due in part to methodological differences between studies. Although current fees are close to diver maximum stated WTP, revenues could potentially be increased by improving the current fee system in ways that users deem acceptable. This potential surplus highlights the value of understanding user perceptions toward MPA fees and management.
Assuntos
Conservação dos Recursos Naturais/economia , Comportamento do Consumidor/economia , Mergulho/economia , Natureza , Conservação dos Recursos Naturais/métodos , Política Ambiental , Humanos , Índias OcidentaisRESUMO
It has been argued that strategies to manage natural areas important for tourism and recreation should integrate an understanding of tourist preferences for specific natural features. However, the accuracy of tourist recalled perceptions of environmental attributes, which are usually derived from post hoc surveys and used to establish management priorities, is currently unmeasured. We tested the validity of the relationship between tourist-stated preferences and actual condition of coral reefs around the Caribbean island of Bonaire. Using standardized questionnaires, we asked 200 divers to select their most and least favorite dive sites and the attributes that contributed to that selection. We also carried out ecological surveys at 76 of the 81 dives sites around the island to assess the actual conditions of the attributes indicated as important for site selection. Fish- and coral-related attributes were key features affecting dive enjoyment. In general, divers appeared to be able to perceive differences between sites in the true condition of biological attributes such as fish species richness, total number of fish schools, live coral cover, coral species richness, and reef structural complexity, although men and women divers differed in their ability to perceive/recall some of the attributes. Perceived differences in environmental attributes, such as surface conditions, underwater current, and the likelihood of encountering rare fish and sea turtles, were not empirically validated. The fact that divers perceive correctly differences in the condition of some of the key biological attributes that affect dive enjoyment reinforces the need to maintain overall reef condition at satisfactory levels. However, variation in accuracy of perceptions owing to demographic factors and attribute type suggests the need for caution when using public perceptions to develop environmental management strategies, particularly for coral reefs.
Assuntos
Antozoários , Conservação dos Recursos Naturais/métodos , Comportamento do Consumidor/estatística & dados numéricos , Mergulho , Ecossistema , Animais , Feminino , Humanos , Masculino , Antilhas Holandesas , Densidade Demográfica , Fatores Sexuais , Especificidade da Espécie , Estatísticas não Paramétricas , Inquéritos e QuestionáriosRESUMO
The exact nature of many interspecific interactions remains unclear, with some evidence suggesting mutualism and other evidence pointing to parasitism for the same pair of interacting species. Here, we show spatial variation in the outcome of the cleaning relationship between Caribbean cleaning gobies (Elacatinus evelynae) and longfin damselfish (Stegastes diencaeus) over the distribution range of these species, and link this variation to the availability of ectoparasites. Cleaning interactions at sites with more ectoparasites were characterized by greater reductions in ectoparasite loads on damselfish clients and lower rates of removal of scales and mucus (i.e. cheating) by cleaning gobies, whereas the opposite was observed at sites where ectoparasite abundance was lower. For damselfish clients, cleaning was therefore clearly mutualistic in some locations, but sometimes neutral or even parasitic in others. Seasonal variability in ectoparasite abundance may ensure that locally low parasite availability, which promotes cleanerfish cheating, may be a transient condition at any given site. Conflicting conclusions about the nature of cleaning symbioses may, therefore, be explained by variation in ectoparasite abundance.