People always say that the early bird gets the worm, but sometimes it may be better for the bird to be fashionably late. In this study we show that interactions between the undersea analogue of the bird and the worm (a carnivorous hawkfish and it’s peanut-sized prey community of small bit fish) are highly dependent on the timing at which predators arrive to the community relative to their prey. We show that later arriving predators more strongly affect prey communities relative to early arriving predators by having greater negative effects on the size of prey communities and modifying prey community composition. Furthermore we demonstrate that predators can promote higher species diversity through increasing the amount of beta diversity (i.e. species turnover). The prevalence of asymmetry in the sequence of species arrival to reefs is highly relevant to marine systems that are often characterized by their high variability in recruitment both within and among different levels of the food web. Collectively our project shows that timing of predator arrival can have demonstrable effects that have been largely ignored in the previous literature on predator-prey dynamics. Furthermore we show novel ways in which natural enemies may promote the coexistence of species in diverse tropical marine systems.

This manuscript represents one in a series of studies that have examined the importance of sequence and timing of species arrival in driving community assembly. Please check out our other papers that feature a guild of competing coral reef fishes.

Geange S.W., J.S. Shima, and A.C. Stier. 2013. An evaluation of competitive effect and response in three species of coral reef fish. 2013. Marine Ecology Progress Series. 472: 239-248. PDF

Geange S.W. and A.C. Stier.2010. Priority effects and habitat complexity affect the strength of competition. Oecologia. 1: 111-118. Abstract. PDF

Geange S.W. and A.C. Stier. 2009. Order of arrival affects competition in two reef fishes. Ecology. 90: 2868-2878. PDF

This paper is led by: Adrian Stier (me) (University of British Columbia) and coauthored by Shane Geange (University of Victoria Wellington), Kate Hanson (American Museum of Natural History), and Ben Bolker (McMaster University). Download the paper here or e-mail me (adrian.stier@gmail.com) for a copy of the manuscript.

Illegal shark fishing is thought to occur globally, including within so-called “shark sanctuaries”, marine reserves and even inside UNESCO World Heritage sites, such as the Galápagos Islands. Presumably, this is due to poor local enforcement coupled with the growing international demand (and high economic incentives) for shark and other wildlife products. Understanding illegal shark fishing practices, and specifically catch composition, is important as poaching is identified as a causal factor of global declines in shark populations. Unfortunately, reliable quantitative data on illegal shark fishing are scarce. Here, the catch onboard an illegal shark fishing vessel seized within the borders of the Galápagos Marine Reserve was documented. A total of 379 sharks from seven shark species were found onboard the vessel. A large fraction of the illegal catch was comprised of both female and juvenile sharks (64% and 89%, respectively). Despite numerous recent advances in shark conservation worldwide, this study demonstrates illegal shark fishing is an ongoing concern and that stricter enforcement and legislation is urgently needed, particularly in areas of high biodiversity.

This work was authored by Lindsey A.Carr, Adrian C. Stier (me), Katharina Fietz, Ignacio Montero, Austin J. Gallagher, and John F.Bruno. The original paper can be found here, or email me directly if interested for a copy. 

Interspecific competition is often asymmetric, and it can limit the spatial distributions of competitively inferior species within a community. When asymmetric competition involves 2 or more component species, the ranking of species’ competitive abilities may form competitive hierarchies (all species of higher rank out-compete all species of lower rank) or competitive networks (at least 1 species of lower rank out-competes ≥1 species of higher rank). Expectations of resource monopolization and patterns of distribution and abundance among species in competitive networks are expected to differ from those in competitive hierarchies. We conducted a field experiment to evaluate the relative competitive abilities of juveniles of 3 closely related species of reef fish (bird wrasse Gomphosus varius, fivestripe wrasse Thalassoma quinquevittatum and the sixbar wrasse T. hardwicke) on Moorea, French Polynesia. We controlled for intrinsic variation in survivorship among species and found that competition among these 3 species was highly asymmetric, resulting in a simple competitive hierarchy (sequence of competitive ability from superior to inferior competitors): fivestripe wrasse > bird wrasse > sixbar wrasse. We surveyed densities of the 3 reef fish species on 55 patch reefs and observed significant negative spatial covariation between superior and inferior competitors, consistent with competitive hierarchies that limit the spatial distributions of the inferior species (sixbar wrasse). Our work demonstrates that intense asymmetric competition and the formation of competitive hierarchies may be an important determinant of resource monopolization and patterns of distribution and abundance in reef fishes.

This paper was authored by Shane W. Geange, Adrian C. Stier (me), and Jeffrey S. Shima. You can find a copy of the manuscript here, or contact me directly for a PDF. 

Numerous studies have argued that the dynamics of species within food webs are poorly predicted by summing pairwise interactions between each species. Such deviations in the observed effect of multiple species operating concurrently that differ from the expected effect of pairwise interactions are known as higher-order interactions. Understanding the prevalence of higher-order interactions and the degree to which they modify community dynamics is critical to advancing community ecology from a field that has largely focused on phenomena description to one that emphasizes prediction. To date, most studies of higher order interactions have focused on describing the existence of higher order interactions using species modules (e.g., two predators and one prey). While such studies have emphasized the importance of both predator antagonism and synergy as extant phenomena in simplified communities, the degree to which higher-order interactions permeate in more complex food webs that contain diverse predator and prey assemblages remains poorly understood. For over 30 years ecologists have studied predator-predator interactions including cooperation, competition, and intraguild predation to gain greater insight into the role of predators in affecting the structure and function of ecosystems. Our understanding of the importance and prevalence of predator-predator interactions in driving ecological communities is, however, only as good as the methods we use to statistically test for these interactions. Here, we describe challenges and possible bias associated with traditional experimental design and statistical approaches that are driven by the heavy depletion of prey throughout experiments. We offer an analytical solution to studies where extensive prey depletion occurs and also provide suggestions for how empiricists can design experiments to limit bias associated with depletion. Our study has important implications for our understanding of how predator diversity affects ecosystem structure and function. Such effects of predator diversity are critical to understand, because species that are higher on the food chain often suffer greater effects from activities such as harvesting, habitat fragmentation, toxin bioaccumulation, and habitat degradation.

This paper is led by: Mike McCoy (Eastern Carolina University) and coauthored by Craig Osenberg and Adrian Stier (me). Our work was generously funded by the National Science Foundation.

McCoy M.W., Stier A.C., and C.W. Osenberg. 2012. Emergent effects of multiple predators on prey survival. The importance of depletion and the functional response. Ecology Letters. 15: 1449-1456. PDF

A new book on Marine Protected Areas (MPAs) edited by Joachim Claudet is now available from Cambridge University Press. In chapter 7 of this book we explore the evaluation of MPAs using different impact assessment designs (Control-Impact, Before-After-Control-Impact, and Before-After-Control-Impact-Paired-Series) as well as the possibility of covarying effects of biogenic habitat and fish populations in affecting estimates of MPA effectiveness.

This chapter is led by Craig Osenberg (UF) and co Authored by  Jeff Shima (UVW), Sonja Miller, (UVW), and Adrian Stier (me, UF).

From the Book Flyer:

“Human-induced environmental disturbance – through fishery activities, coastal development, tourism and pollution – is a major challenge to the restoration and conservation of marine biodiversity. Synthesizing the latest research into marine biodiversity conservation and fisheries management, this book provides regional and global perspectives on the role of Marine Protected Areas (MPAs) in confronting this challenge. The approach is multidisciplinary, covering all the fields involved in designating and assessing MPAs: ecology, fisheries science, statistics, economics, sociology and genetics. The book is structured around key topics, including threats to marine ecosystems and resources, the effects and effectiveness of MPAs and the scaling-up of MPA systems. Both theoretical and empirical approaches are considered. Recognizing the diversity of MPA sciences, the book also includes one part designed specifically as a practical guide to implementing scientific assessment studies of MPAs and monitoring programs.”

We published a synthetic review on costal and estuarine ecosystem services that appears in the May (2011) issue of Ecological Monographs. Our working group includes experts that range over a variety of different ecosystems (Edward B. Barbier, Sally D. Hacker, Chris Kennedy, Evamaria W. Koch, Adrian C. Stier (me), and Brian R. Silliman). We review the main ecological services across systems including marshes, mangroves, nearshore coral reefs, seagrass beds, sand beaches, and sand dunes. Where possible, we indicate estimates of the key economic values arising from these services, and discuss how the natural variability of estuary and coastal ecosystems (ECEs) impacts their benefits, the synergistic relationships of ECEs across seascapes, and management implications.

See the full abstract and download the paper here or e-mail me (adrian.stier@gmail.com) for a copy of the manuscript

The influence of predation on the growth of stony corals has gained increased attention, although the degree to which coral conspecific density can modify the effects of corallivores remains poorly studied. Here, a field experiment was used to quantify the independent and combined effects of coral colony density and coral predators on the skeletal growth of massive Porites. Predator exclusion increased coral growth by 20%. Increasing coral density increased growth by 30%. However, the effect of predators was independent of coral density. Possible alternative mechanisms for increased skeletal growth at higher colony density include changes in near-field flow, resulting in increases in photosynthetic activity, nutrient uptake, or the increased accessibility of coral mutualists.

This paper was authored by A. A. Shantz, A. C. Stier (me), and J. A. Idjadi. You can find a copy of the manuscript here, or contact me directly for a PDF. 

Predation risk experienced by individuals living in groups depends on the balance between predator dilution, competition for refuges, and predator interference or synergy. These interactions operate between prey species as well: the benefits of group living decline in the presence of an alternative prey species. We apply a novel model-fitting approach to data from field experiments to distinguish among competing hypotheses about shifts in predator foraging behavior across a range of predator and prey densities. Our study provides novel analytical tools for analyzing predator foraging behavior and offers insight into the processes driving the dynamics of coral reef fish.

Studies of predator foraging behavior typically focus on single prey species and fixed predator densities, ignoring the potential importance of complexities such as predator dilution; predator-mediated effects of alternative prey; heterospecific competition; or predator–predator interactions. Neglecting the effects of prey density is particularly problematic for prey species that live in mixed species groups, where the beneficial effects of predator dilution may swamp the negative effects of heterospecific competition. Here we use field experiments to investigate how the mortality rates of a shoaling coral reef fish (a wrasse: Thalassoma amblycephalum), change as a result of variation in: 1) conspecific density, 2) density of a predator (a hawkfish: Paracirrhites arcatus), and 3) presence of an alternative prey species that competes for space (a damselfish: Pomacentrus pavo). We quantify changes in prey mortality rates from the predator's perspective, examining the effects of added predators or a second prey species on the predator's functional response. Our analysis highlights a model-fitting approach that discriminates amongst multiple hypotheses about predator foraging in a community context. Wrasse mortality decreased with increasing conspecific density (i.e. mortality was inversely density-dependent). The addition of a second predator doubled prey mortality rates, without significantly changing attack rate or handling time – i.e. there was no evidence for predator interference. The presence of a second prey species increased wrasse mortality by 95%; we attribute this increase either to short-term apparent competition (predator aggregation) or to a decrease in handling time of the predator (e.g. through decreased wrasse vigilance). In this system, 1) prey benefit from intraspecific group living though a reduced predation risk, and 2) the benefit of group living is reduced in the presence of an alternative prey species.

This paper was authored by Adrian C. Stier (me), Shane W. Geange, and Benjamin M. Bolker. You can find a copy of the manuscript here, or contact me directly for a PDF. 

Coral and rocky reef fish populations are widely used as model systems for the experimental exploration of density-dependent vital rates, but patterns of density-dependent mortality in these systems are not yet fully understood. In particular, the paradigm for strong, directly density-dependent (DDD) postsettlement mortality stands in contrast to recent evidence for inversely density-dependent (IDD) mortality. We review the processes responsible for DDD and IDD per capita mortality in reef fishes, noting that the pattern observed depends on predator and prey behavior, the spatial configuration of the reef habitat, and the spatial and temporal scales of observation. Specifically, predators tend to produce DDD prey mortality at their characteristic spatial scale of foraging, but prey mortality is IDD at smaller spatial scales due to attack-abatement effects (e.g., risk dilution). As a result, DDD mortality may be more common than IDD mortality on patch reefs, which tend to constrain predator foraging to the same scale as prey aggregation, eliminating attack-abatement effects. Additionally, adjacent groups of prey on continuous reefs may share a subset of refuges, increasing per capita refuge availability and relaxing DDD mortality relative to prey on patch reefs, where the patch edge could prevent such refuge sharing. These hypotheses lead to a synthetic framework to predict expected mortality patterns for a variety of scenarios. For nonsocial, nonaggregating species and species that aggregate in order to take advantage of spatially clumped refuges, IDD mortality is possible but likely superseded by DDD refuge competition, especially on patch reefs. By contrast, for species that aggregate socially, mortality should be IDD at the scale of individual aggregations but DDD at larger scales. The results of nearly all prior reef fish studies fit within this framework, although additional work is needed to test many of the predicted outcomes. This synthesis reconciles some apparent contradictions in the recent reef fish literature and suggests the importance of accounting for the scale-sensitive details of predator and prey behavior in any study system.

This paper was authored by J. Wilson White, Jameal F. Samhouri, Adrian C. Stier (me),
Clare L. Wormald, Scott L. Hamilton, Stuart A. Sandin. You can find a copy of the manuscript here, or contact me directly for a PDF. 

Adding or restoring habitat can alter the production of habitat-dependent organisms in two contrasting ways: (1) by enhancing input of new colonists to the new sites (the Field-of-Dreams Hypothesis); and (2) by drawing colonists away from existing sites (the Propagule Redirection Hypothesis), and thus reducing the deleterious effects of density. We conducted a field experiment on coral reef fishes in Moorea, French Polynesia, to quantify how differing levels of habitat availability (controlling for quality) increased and/or redirected colonizing larval fish. Focal reefs without neighboring reefs received two to four times more settlers than reefs with adjacent habitat, demonstrating that increased habitat redirected larval fish. At the scale of the entire reef array, total colonization increased 1.3-fold in response to a sixfold increase in reef area (and a 2.75-fold increase in adjusted habitat availability). Thus, propagules were both increased and redirected, a result midway between the Field-of-Dreams and Propagule Redirection Hypotheses. A recruitment model using our data and field estimates of density-dependent recruitment predicts that habitat addition increases recruitment primarily by ameliorating the negative effects of competition at existing sites rather than increasing colonization at the new sites per se. Understanding long-term implications of these effects depends upon the interplay among habitat dynamics, population connectivity, colonization dynamics, and density dependence.

This paper is authored by Craig Osenberg (University of Florida) and Adrian Stier (me, University of Florida) and appears in the October issue of Ecology, 2010. 

Coral reefs are one of the most diverse systems on the planet; yet, only a small fraction of coral reef species have attracted scientific study. Here, we document strong deleterious effects of an often overlooked species-the vermetid gastropod, Dendropoma maximum-on growth and survival of reef-building corals. Our surveys of vermetids on Moorea (French Polynesia) revealed a negative correlation between the density of vermetids and the per cent cover of live coral. Furthermore, the incidence of flattened coral growth forms was associated with the presence of vermetids. We transplanted and followed the fates of focal colonies of four species of corals on natural reefs where we also manipulated presence/absence of vermetids. Vermetids reduced skeletal growth of focal corals by up to 81 per cent and survival by up to 52 per cent. Susceptibility to vermetids varied among coral species, suggesting that vermetids could shift coral community composition. Our work highlights the potential importance of a poorly studied gastropod to coral dynamics.

This paper was authored by Shima JS, Osenberg CW, and Stier AC (me). You can find a copy of the manuscript here, or contact me directly for a PDF. 

Both habitat complexity and priority effects can influence the strength of competitive interactions; however, the independent and synergistic effects of these processes are not well understood. In Moorea, French Polynesia, we conducted a factorial field experiment to quantify the independent and combined effects of priority effects and habitat complexity on the strength of intraspecific competitive interactions among recently settled individuals of a coral reef fish (Thalassoma quinquevittatum: Labridae). Simultaneous arrival of focal individuals with competitors resulted in a 2.89-fold increase in survival relative to reefs where focal individuals arrived 5 days later than competitors (i.e., a priority effect). Increasing habitat complexity resulted in a 1.55-fold increase in survivorship when focal individuals arrived simultaneously with or before competitors. However, increasing habitat complexity did not affect the survivorship of focal individuals arriving 5 days later than competitors. Behavior observations showed that survivorship was negatively correlated with aggression. Aggression by prior residents towards focal individuals was significantly greater when focal individuals arrived 5 days later than competitors than when they arrived simultaneously. Increasing habitat complexity did not reduce aggression. Our results suggest that, when competitors arrive simultaneously, competitive interactions are weak and subordinates are not displaced from complex habitat; increasing habitat complexity increases survival by disrupting predation. Conversely, when competitors arrive at different times, aggression intensifies and increasing habitat complexity does not disrupt predation because competitive subordinates are excluded from habitat resources. This study demonstrates that the strength of competition can be context-dependent and may vary with the timing of competitive interactions and habitat complexity.

This paper was authored by Shane W. Geange and Adrian C. Stier (me). You can download the manuscript here, or email me for a copy of the PDF.

The trophic ecology of cyanobacterial blooms is poorly understood on coral reefs. Blooms of toxic cyanobacteria, Lyngbyamajuscula, can quickly form large mats. The herbivorous sea hare, Stylocheilus striatus, and the predatory nudibranch, Gymnodoris ceylonica, often associate with these blooms, forming a linear food chain: nudibranch—sea hare—cyanobacteria. Using laboratory studies, this study quantified (1) the functional response of nudibranchs, (2) the effect of sea hare size on predation rates, and (3) the strength of the indirect effect of sea hare predation on cyanobacteria (i.e., a trophic cascade). Nudibranchs consumed on average 2.4 sea hares d−1, with the consumption of small sea hares 22 times greater than the consumption of large sea hares. Predation of sea hares reduced herbivory. Cyanobacterial biomass was 1.5 times greater when nudibranchs were present relative to when nudibranchs were absent. Although sea hare grazing can substantially reduce cyanobacterial biomass, predation of sea hares may mitigate grazing pressure, and therefore increase the abundance of cyanobacteria.

This paper was authored by Shane W. Geange and Adrian C. Stier (me). You can find a copy of the manuscript here, or contact me directly for a PDF. 

Predators have important effects on coral reef fish populations, but their effects on community structure have only recently been investigated and are not yet well understood. Here, the effect of predation on the diversity and abundance of young coral reef fishes was experimentally examined in Moorea, French Polynesia. Effects of predators were quantified by monitoring recruitment of fishes onto standardized patch reefs in predator-exclosure cages or uncaged reefs. At the end of the 54-day experiment, recruits were 74% less abundant on reefs exposed to predators than on caged ones, and species richness was 42% lower on reefs exposed to predators. Effects of predators varied somewhat among families, however, rarefaction analysis indicated that predators foraged non-selectively among species. These results indicate that predation can alter diversity of reef fish communities by indiscriminately reducing the abundance of fishes soon after settlement, thereby reducing the number of species present on reefs.

This paper was authored by J.M. Heinlein, A.C. Stier (me), and M.A. Steele. You can find a copy of the manuscript here, or contact me directly for a PDF. 

Many communities experience repeated periods of colonization due to seasonally regenerating habitats or pulsed arrival of young-of-year. When an individual's persistence in a community depends upon the strength of competitive interactions, changes in the timing of arrival relative to the arrival of a competitor can modify competitive strength and, ultimately, establishment in the community. We investigated whether the strength of intracohort competitive interactions between recent settlers of the reef fishes Thalassoma hardwicke and T. quinquevittatum are dependent on the sequence and temporal separation of their arrival into communities. To achieve this, we manipulated the sequence and timing of arrival of each species onto experimental patch reefs by simulating settlement pulses and monitoring survival and aggressive interactions. Both species survived best in the absence of competitors, but when competitors were present, they did best when they arrived at the same time. Survival declined as each species entered the community progressively later than its competitor and as aggression by its competitor increased. Intraspecific effects of resident T. hardwicke were similar to interspecific effects. This study shows that the strength of competition depends not only on the identity of competitors, but also on the sequence and timing of their interactions, suggesting that when examining interaction strengths, it is important to identify temporal variability in the direction and magnitude of their effects. Furthermore, our findings provide empirical evidence for the importance of competitive lotteries in the maintenance of species diversity in demographically open marine systems.

This paper was authored by Shane W. Geange and Adrian C. Stier (me). You can find a copy of the manuscript here, or contact me directly for a PDF. 

Between January and July 2008, we observed an unusual association between several species of coral reef fishes and the corallivorous crown-of-thorns seastar Acanthaster planci within the lagoon of Moorea, French Polynesia (17°30′S: 149°50′W). Four species of recently settled damselfishes (Pomacentrus pavo, Dascyllus aruanus, D. flavicaudus, and D. trimaculatus) as well as juveniles and adults of a cardinalfish (Siphamia sp.) were seen sheltering within the venomous spines of Acanthaster. Three of the damselfish species normally occupy branching corals throughout their lives, one occupies sea anemones when young and shifts to general coral reef habitat when older, and the cardinalfish, an undescribed species (O. Gon and J. Randall, pers. comm.), appears to normally associate with sea urchins.

Fishes only inhabited Acanthaster when the seastars occurred on sandy substrate at least several meters away from corals. Surveys done in January along four 200 × 10 m transects (5, 10, 15, and 20 m depth) revealed that 6 out of 29 Acanthaster were occupied by cardinalfish (2–18 fish per seastar, mean = 6.2). All occupied seastars were more than 5 m from the reef, whereas none of the Acanthaster less than 5 m from the reef contained fishes. The four damselfish species noted above were not seen during this survey, but we observed them occupying Acanthaster at other times during January (Fig. 1), also only when the host seastar was distant from the reef. During surveys in June along three transects (5, 10, and 20 m depth), we observed 11 Acanthaster and three of these that were more than 5 m from the reef were occupied by cardinalfish (2–9 per seastar, mean = 4.3) and one also had a single damselfish that was too small and unpigmented to identify. Dascyllus flavicaudus and Siphamia sp. (upper left) sheltering amongst the spines of Acanthaster planci. 

We know no prior records of damselfishes occupying Acanthaster. The outcome of this apparently short-term, opportunistic, commensal relationship is unclear. Only recently settled damselfishes were seen inhabiting Acanthaster, implying that individuals either move to more typical habitat after settling on Acanthaster, perhaps when seastars move near the reef, or die. In contrast, all life stages of the cardinalfish Siphamia sp., from recent settlers to adults mouthbrooding eggs were found on Acanthaster, as has been noted for other members of this genus (e.g., Allen 1972). These observations reveal previously unappreciated flexibility in the range of habitats used by several coral reef fishes. Future studies will be necessary to document whether this association persists beyond the current outbreak of Acanthaster and to determine the types and magnitude of potential effects on the population dynamics of the fish species involved.

This paper was authored by Adrian C. Stier (me), Mark A. Steele, and Andrew J. Brooks. You can find a copy of the note here, or contact me directly for a PDF. 

Ecological research within coral reefs often requires the use of anesthetics to immobilize organisms. It is therefore important to consider the effect of these chemicals on the surrounding flora and fauna, particularly to the corals themselves. We quantified the effects of clove oil, a commonly used fish anesthetic, on the growth and occurrence of bleaching in three species of corals: Acropora striata, Pocillopora verrucosa, and Porites australiensis. We compared coral responses to five treatments: a gradient of four clove oil concentrations (0-28%) in seawater, and one concentration of clove oil (14%) in ethanol. Each week, we assessed the presence of bleaching, and then applied the treatment. We measured growth over the duration of the 6-week experiment using the buoyant weight technique. Growth and bleaching showed a dose response to clove oil exposure, and the use of ethanol as a solvent had an additional deleterious effect, as also suggested by observed changes in concentrations of eugenol following field application. Overall, growth was reduced by 37.6% at the highest concentration (28% clove oil in seawater) relative to the control (0% clove oil). The reduction in growth was nearly as great (35.3% of the control) at half the concentration of clove oil (14%) when dissolved in ethanol. These results suggest the repeated use of clove oil (even without a solvent) can deleteriously affect corals.

The manuscript relating to this work was authored by S.E. Boyer, J.S. White, A.C. Stier (me), and C.W. Osenberg. The paper can be accessed here or contact me via email for a copy