Caribbean Coral Reef Fishes Research Articles

Vertical limits of host infestation by gnathiid isopods (Isopoda: Gnathiidae) parasitic on Caribbean coral reef fishes

Abstract Parasites play significant roles in the function of ecosystems and can make up a large proportion of overall biomass. Yet, fundamental aspects of their ecology are often understudied relative to other organisms. Gnathiid isopods are the primary ectoparasites of fishes in coral reef ecosystems. While some studies have investigated their host-detection capabilities, the means by which they seek hosts are largely unknown. Gnathiids are benthic and live on the bottom, and all collection efforts involving live hosts have thus far involved traps set at or near the reef substrate. We investigated the distance gnathiids will travel vertically in the water column to attach to a fish host. The majority of gnathiids collected were at or less than 1 m above the reef substrate, and gnathiids were collected in serially diminishing numbers at 2 and 3 m above it. No gnathiids were collected from any fish hosts set more than 3.5 m above the reef substrate. Results suggest that gnathiids will actively seek host fishes in situ and will travel further from their benthic habitat than previously known. By swimming into the water column, gnathiids can exploit larger, highly-mobile fishes, which can serve as a major source of dispersal.

Evolution: Genomic Signatures of Mimicry and Mimicry of Genomic Signatures

How new species form in the ocean, and thus what determines the diversity of fish in the sea, is not wellunderstood. A study in Caribbean coral-reef fishes sheds light on the genomic underpinnings of diversification in the marine realm.

Host‐dependent differences in resource use associated with Anilocra spp. parasitism in two coral reef fishes, as revealed by stable carbon and nitrogen isotope analyses

AbstractThe role of parasites in trophic ecology is poorly understood in marine ecosystems. Stable isotope analyses (SIA) have been widely used in studies of trophic ecology, but have rarely been applied to study the role of parasites. Considering that some parasites are associated with altered host foraging patterns, SIA can help elucidate whether parasitism influences host trophic interactions. French grunt (Haemulon flavolineatum), an abundant Caribbean coral reef fish, contributes greatly to trophic connectivity. They typically depart the reef at dusk, feed overnight in seagrass beds, and return to the reef at dawn. The large parasitic isopod Anilocra haemuli commonly infects French grunt, and infected fish are less likely to complete their diel migration, and are in poorer condition than uninfected conspecifics. Brown chromis (Chromis multilineata) are diurnally feeding planktivores and infection by Anilocra chromis does not influence host condition. To determine if Anilocra infection influences host diet and foraging locality, we conducted stable carbon and nitrogen isotope analyses on scale, muscle, heart and gill tissues of infected and uninfected French grunt and brown chromis. We determined that all French grunt had δ13C values representative of seagrass habitats, but infected French grunt were significantly enriched in 13C and 15N compared to uninfected conspecifics. This suggests that compared to uninfected conspecifics, infected French grunt forage in seagrass, but on isotopically enriched prey, and/or are in poorer condition, which can elevate δ13C and δ15N values. For brown chromis, infection did not significantly influence any δ13C and δ15N values; hence they all foraged in the same environment and on similar prey. This is the first study to use SIA to examine differences in resource use by Caribbean coral reef fishes associated with parasitism and to evaluate how closely related parasites might have host‐dependent effects on host trophic ecology.

Eastern Caribbean Circulation and Island Mass Effect on St. Croix, US Virgin Islands: A Mechanism for Relatively Consistent Recruitment Patterns.

The northeastern Caribbean Sea is under the seasonal influence of the Trade Winds but also of the Orinoco/Amazon freshwater plume. The latter is responsible for intensification of the Caribbean Current in general and of its eddy activity in the northern part of the Caribbean Sea. More importantly, we show in this study that the front of the freshwater plume drives a northward flow that impinges directly on the island of St. Croix in the United States Virgin Islands. The angle of incidence of the incoming flow controls the nature of the wake on both sides and ends of the island, which changes from cyclonic to anticylonic wake flow, with either attached or shed eddies. Using an off-line bio-physical model, we simulated the dispersal and recruitment of an abundant Caribbean coral reef fish, the bluehead wrasse (Thalassoma bifasciatum) in the context of the wake flow variability around St. Croix. Our results revealed the role played by the consistent seasonal forcing of the wake flow on the recruitment patterns around the island at the interannual scale. The interannual variability of the timing of arrival and northward penetration of the plume instead controls the nature of the wake, hence the regional spatial recruitment patterns.

Multiyear Tracking of Nassau Grouper Spawning Migrations

AbstractAn understanding of temporal patterns of migration and spatial connectivity between home ranges and spawning sites is necessary for effective management of species that form transient spawning aggregations. The Nassau Grouper Epinephelus striatus is a Caribbean coral reef fish that displays such spawning aggregations, which have been overfished to the point of threatening the species. Using acoustic telemetry, we examined the size at which Nassau Grouper migrate to spawning aggregations, the timing of migrations, and the distance of migration routes used by Nassau Grouper from within and outside of a large, no‐take marine reserve in the central Bahamas. Fish (total n = 19) were tagged in 2004 (n = 6) and 2005 (n = 13) and were tracked for one to four spawning seasons. Fish that were 54 cm TL or greater made spawning migrations, with all but one migrating southward along the shelf edge of Exuma Sound for a distance of 70 km to over 200 km, usually during the December full moon. Fish typically made one migration annually, which lasted from 1 to 3 weeks, with fish remaining at spawning sites for only 1–2 d; however, when the full moon was early in the spawning season, several fish remained away from their home reefs through two lunar cycles or delayed their migrations by a month, and one fish made two migrations. Fish that were migrating for the first time had slower swimming speeds to spawning sites than did experienced fish, but swimming speeds were similar between the two groups during return migrations, suggesting that their migration behavior was learned. Our results demonstrate that spawning migration patterns for this species may be more variable in The Bahamas than at other Caribbean locations. The present findings also have important implications for the management of the species, including increasing the minimum size limit to 54 cm or larger and the use of both marine protected areas and seasonal closures to rebuild the spawning stock.Received February 1, 2016; accepted July 27, 2016

Do males measure body sizes of males and females similarly? A test in the beaugregory damselfish, Stegastes leucostictus

Body length in fishes appears to serve as a “signal” for intra-sexual selection (i.e., male–male competition) and inter-sexual selection (i.e., mate choice). Previous studies indicate that the size of males correlates with the ability to gain or control resources from other males, while the size of females corresponds to features related to reproductive success such as fecundity. However, it remains unclear whether male size, as it relates to success in territory defense, is assessed similarly to female size as it relates to fecundity. Using the beaugregory damselfish (Stegastes leucostictus), a Caribbean coral reef fish, we examined whether focal males measure the “signal”, body length, similarly in both sexes. We presented focal territorial males with pairs of males and pairs of females that differed in size by varying degrees, and judged whether the focal male used size to differentiate between the two stimuli. We found that focal males did respond differently based on sex (spent more time near the two male stimuli) and size (spent more time near the larger fish) but did not respond to size differences based on sex. Thus, focal males measured size differences in both sexes similarly in spite of the size reflecting different attributes in males and females.

Decreased movement related to parasite infection in a diel migratory coral reef fish

Risk of infection by parasites may be an important contributing cause or consequence of animal movement patterns. The diel movement patterns of French grunt, a common Caribbean coral reef fish, are well documented and known to connect reef and seagrass habitat. In the northeastern Caribbean, French grunts are known to be infected by Anilocra haemuli, one of the largest and most conspicuous ectoparasitic isopods. Studies on Anilocra infection have demonstrated that infection reduces host swimming performance and condition and may alter host behavior. We tested predictions of the hypothesis that A. haemuli infection influences the movement patterns of host French grunt, specifically whether short-distance daytime movements and/or reef–seagrass migration at dusk was associated with infection. We conducted focal observations on infected and uninfected fish during both daytime resting and dusk migration periods. We also conducted daytime and nocturnal surveys in reef habitat, documenting changes in the proportion of infected individuals. We found that infected fish move significantly less than uninfected conspecifics during the day and observed 100 % of uninfected focal fish and 37.5 % of infected focal fish departing the reef during dusk. In reef habitat, the proportion of fish infected with Anilocra was also significantly greater at night compared to daytime. We suggest that A. haemuli infection alters host movement patterns and that parasitism may therefore indirectly influence trophic connectivity between reef and seagrass ecosystems.

Growth potential and predation risk drive ontogenetic shifts among nursery habitats in a coral reef fish

ABSTRACT: Various species of aquatic animals have complex life cycles and utilize differenthabitats during consecutive phases of their life cycles. For example, many marine fish speciesoccupy different habitat types during juvenile and adult life stages. Juveniles of some speciesrecruit to inshore nursery habitats such as mangroves and seagrass beds, whereas large adultstend to dominate coral reefs. The mechanisms underlying apparent cross-habitat distribution pat-terns by life stage remain uncertain for many species. Here, we investigated potential mecha-nisms that produce a 5-phase, and possibly even a 6-phase life cycle pattern in a common Carib-bean coral reef fish species Haemulon flavolineatum (French grunt) across multiple coastalhabitats. At each discrete life stage, individuals were faced with important and stage-specific eco-logical trade-offs that could significantly augment fitness. Pelagic larvae settled on rubble habitatsnear bay entrances where they reached an optimum between predation risk (survival) and foodabundance (growth). Individuals subsequently shifted to seagrass beds, likely as a result of in -creased food resources, followed by a shift to mangroves as predation refugia. Before the uni-directional movement between bays and coral reefs, some fishes shifted from mangroves to boul-der/notch habitats. Likely, this habitat serves as an intermediate stop before their final shift to thecoral reef, where they reach maturity and reproduce. This study reveals ecological linkages andflows among habitat types that are of direct conservation importance to these ecosystems. Further-more, the identification of mechanisms that give rise to cross-habitat distribution patterns of mar-ine fishes in general might lead to enhanced conservation management solutions to declines infisheries at larger scales.KEY WORDS: Ontogenetic habitat shifts · Life cycle · Nursery · Food abundance · Condition ·Maturation · Trade-offs

Antipredator responses to invasive lionfish, Pterois volitans: interspecific differences in cue utilization by two coral reef gobies

Understanding prey response to predators and their utilization of sensory cues to assess local predation risk is crucial in determining how predator avoidance strategies affect population demographics. This study examined the antipredator behaviors of two ecologically similar species of Caribbean coral reef fish, Coryphopterus glaucofraenum and Gnatholepis thompsoni, and characterized their responses to different reef predators. In laboratory assays, the two species of gobies were exposed to predator visual cues (native Nassau grouper predator vs. invasive lionfish predator), damage-released chemical cues from gobies, and combinations of these, along with appropriate controls. Behavioral responses indicate that the two prey species differ in their utilization of visual and chemical cues. Visual cues from predators were decisive for both species’ responses, demonstrating their relative importance in the sensory hierarchy, whereas damage-released cues were a source of information only for C. glaucofraenum. Both prey species could distinguish between native and invasive predators and subsequently altered their antipredator responses.

Perspective: Matching, Mate Choice, and Speciation

Matching was developed in the 1960s to match such entities as residents and hospitals, colleges and students, or employers and employees. This approach is based on "preference lists," whereby each participant ranks potential partners according to his/her preferences and tries to match with the highest-ranking partner available. Here, we discuss the implications of matching for the study of mate choice and speciation. Matching differs from classic approaches in several respects, most notably because under this theoretical framework, the formation of mating pairs is context-dependant (i.e., it depends on the configuration of pairings in the entire population), because the stability of mating pairs is considered explicitly, and because mate choice is mutual. The use of matching to study mate choice and speciation is not merely a theoretical curiosity; its application can generate counter-intuitive predictions and lead to conclusions that differ fundamentally from classic theories about sexual selection and speciation. For example, it predicts that when mate choice is mutual and the stability of mating pairs is critical for successful reproduction, sympatric speciation is a robust evolutionary outcome. Yet the application of matching to the study of mate choice and speciation has been largely dominated by theoretical studies. We present the hamlets, a group of brightly colored Caribbean coral reef fishes in the genus Hypoplectrus (Serranidae), as a particularly apt system to test empirically specific predictions generated by the application of matching to mate choice and speciation.

Local and regional genetic connectivity in a Caribbean coral reef fish

Coupled bio-physical models of larval dispersal predict that the Costa Rica–Panama (CR–PAN) reefs should constitute a demographically isolated region in the western Caribbean. We tested the hypothesis that CR–PAN coral reef fish populations would be isolated from Mesoamerican Barrier Reef System (MBRS) populations. To test that, we assessed population genetic structure in bicolor damselfish (Stegastes partitus) from both regions. Adult fish were genotyped from five reefs in CR–PAN and from four reefs along the MBRS at 12 microsatellite loci. Between-region F ST (F ST = 0.0030, P < 0.005) and exact test (x 2 = 74.34, df = 18, P < 0.0001) results indicated that there is weak but significant genetic differentiation between regions, suggesting some restriction in connectivity along the Central American coastline, as predicted by bio-oceanographic models. Additionally, there is among-site genetic structure in the CR–PAN region, relative to the MBRS and between regions, suggesting higher self-recruitment within CR–PAN. This finding may be explained by differences in habitat characteristics.

Island biogeography of Caribbean coral reef fish

ABSTRACTAim The goal of our study was to test fundamental predictions of biogeographical theories in tropical reef fish assemblages, in particular relationships between fish species richness and island area, isolation and oceanographic variables (temperature and productivity) in the insular Caribbean. These analyses complement an analogous and more voluminous body of work from the tropical Indo‐Pacific. The Caribbean is more limited in area with smaller inter‐island distances than the Indo‐Pacific, providing a unique context to consider fundamental processes likely to affect richness patterns of reef fish.Location Caribbean Sea.Methods We compiled a set of data describing reef‐associated fish assemblages from 24 island nations across the Caribbean Sea, representing a wide range of isolation and varying in land area from 53 to 110,860 km2. Regression‐based analyses compared the univariate and combined effects of island‐specific physical predictors on fish species richness.Results We found that diversity of reef‐associated fishes increases strongly with increasing island area and with decreasing isolation. Richness also increases with increasing nearshore productivity. Analyses of various subsets of the entire data set reveal the robustness of the richness data and biogeographical patterns.Main conclusions Within the relatively small and densely packed Caribbean basin, fish species richness fits the classical species–area relationship. Richness also was related negatively to isolation, suggesting direct effects of dispersal limitation in community assembly. Because oceanic productivity was correlated with isolation, however, the related effects of system‐wide productivity on richness cannot be disentangled. These results highlight fundamental mechanisms that underlie spatial patterns of biodiversity among Caribbean coral reefs, and which are probably also are functioning in the more widespread and heterogeneous reefs of the Indo‐Pacific.

Habitat selection during settlement of three Caribbean coral reef fishes: Indications for directed settlement to seagrass beds and mangroves

We studied the settlement patterns of three Caribbean coral reef fishes in three different habitat types: mangroves, seagrass beds, and coral reefs. The settlement patterns of the three species were not random and could best be explained by active habitat selection during settlement. Acanthurus bahianus preferentially settled on the shallow reef flat and in adjacent seagrass beds, Lutjanus apodus settled exclusively into mangroves, and Ocyurus chrysurus, settled into both mangroves and seagrass beds. The settlement patterns of these three species reflect their habitat utilization during later juvenile stages. This study, therefore, suggests that the higher juvenile densities in mangroves and seagrass beds are determined by habitat selection during settlement rather than by post‐settlement processes. This habitat selection during settlement is in accordance with the assumed importance of mangroves and seagrass beds as juvenile habitats of coral reef fishes and underlines the pressing need for their conservation.

Distributional patterns and community structure of Caribbean coral reef fishes within a river‐impacted bay

This study examined how riverine inputs, in particular sediment, influenced the community structure and trophic composition of reef fishes within Rio Bueno, north Jamaica. Due to river discharge a distinct gradient of riverine inputs existed across the study sites. Results suggested that riverine inputs (or a factor associated with them) had a structuring effect on fish community structure. Whilst fish communities at all sites were dominated by small individuals (&lt;20 cm), diversity and total biomass were reduced with increased proximity to the river mouth. The abundance of all fishes, but particularly small‐bodied, juvenile and herbivorous fishes was reduced in turbid water when compared to clear‐water sites. Results strongly suggest that fluvial sediment inputs may play an important role in structuring fish assemblages even under intense fishing pressure.

Client preferences by Caribbean cleaning gobies: food, safety or something else?

Predation risk is amongst the most pervasive selective pressures influencing behaviour and animals have been repeatedly shown to trade-off foraging success for safety. We examined the nature of this trade-off in cleaning symbioses amongst Caribbean coral reef fishes. We predicted that cleaning gobies (Elacatinus evelynae and Elacatinus prochilos) should prefer fish clients that pose a low risk of predation (e.g. herbivores) over clients that may have more ectoparasites but pose a higher risk (e.g. piscivores). Our field observations revealed that cleaners did clean preferentially client species with more parasites but predatory and non-predatory clients had similar ecto- parasite loads. Despite the lack of a foraging advantage for inspecting predators, cleaners did not avoid risky clients. On the contrary, a larger proportion of visiting predators than non-predators was inspected, gobies initiated more interactions with predatory clients, and predators were attended to immediately upon arrival at cleaning stations. This preferential treatment of dangerous clients may allow the rapid identification of cleaners as non-prey item or may be due to the effect of predators on the rest of the cleaners' clientele, which avoided cleaning stations whilst predators were present. Dealing with potentially risky clients may allow gobies to regain access to their main food source: non-predatory clients.

Environmental variability, early life-history traits, and survival of new coral reef fish recruits

For benthic marine organisms with complex life cycles, conditions experienced by pelagic larvae can influence juvenile survival. Trait-specific selective mortality has been documented in the laboratory and field, yet our knowledge of the factors contributing to the existence, strength, and consistency of natural selective mortality is limited. We compiled previously published and unpublished data on the common Caribbean coral reef fish, Thalassoma bifasciatum, recruiting to Barbados, West Indies, and the upper Florida Keys to examine how environmental variability during pelagic larval life influences the distribution of early life-history traits exhibited by new recruits. We explored how the scope of variability in otolith-derived traits such as larval growth, pelagic larval duration (PLD), size and condition at settlement, and early juvenile growth influences the degree to which mortality of juveniles is selective. At both locations, contrasting oceanographic conditions (periodic passage of large low-salinity North Brazil Current [NBC] rings near Barbados and seasonal variation in water temperature at Florida) led to significant differences in the early life-history traits of recruits. Mortality was most frequently selective for the two most variable traits, condition at settlement and early juvenile growth. Environmental variability (including variation in predation pressure and stress-inducing conditions) also likely influences juvenile mortality and consequently the degree to which selective loss of particular traits occurs. As we begin to better understand the spatial, temporal, and species-specific circumstances in which events occurring during larval life influence juvenile performance, studies must also be extended to examine how these processes are translated into adult fitness.

Habitat Connectivity in Coastal Environments: Patterns and Movements of Caribbean Coral Reef Fishes with Emphasis on Bluestriped Grunt, Haemulon sciurus

Habitat connectivity within tropical marine seascapes may be greatly dependent on the movement of large organisms, particularly fishes. Using visual and trap sampling within two small bays in Virgin Islands National Park/Biosphere Reserve, St. John, U.S. Virgin Islands, we documented that large coral reef fishes, particularly large adult grunts, which shelter by day on coral reefs and make nocturnal feeding migrations into seagrass beds, accounted for the greatest biomass and abundance of fishes sampled in seagrass habitat. Using passive tags and sonic telemetry, we documented the nocturnal migration patterns of large adult grunts (bluestriped grunts, Haemulon sciurus), which are similar to the well-documented migration patterns of juvenile grunts. Large grunts showed high site fidelity to nocturnal foraging sites in seagrass beds. Sonictagged grunts demonstrated little movement in their diurnal shelter sites in the boulder-coral zone, with most individuals making nocturnal migrations into the adjacent seagrass bed. These results provide evidence for strong linkage among adjacent habitats at a small spatial scale and emphasize the importance of inclusion of a diversity of habitats in Marine Protected Areas.

SELECTIVE MORTALITY DURING THE LARVAL–JUVENILE TRANSITION IN TWO CORAL REEF FISHES

For organisms with complex life histories, processes occurring during transitions between stages can strongly affect population dynamics. The major life history transition for many marine species is settlement from pelagic larvae to benthic or demersal juveniles. We examined differential mortality at settlement as a function of early life history traits (size-at-age, growth rates) in three cohorts of two common Caribbean coral reef fishes, Thalassoma bifasciatum and Halichoeres bivittatus (Labridae). We deployed light traps to collect late-stage larvae of each cohort. We also collected juveniles of each cohort at regular intervals (every second day) for two weeks following their first appearance on the nearshore reefs of Barbados, West Indies, during the spring (April–May) and fall (August–October) of 1997. Comparisons of otolith-derived traits exhibited by younger recruits (initial group) to those exhibited by older juveniles (survivor group) revealed that there was a difference in otolith growth during ...

Integrating individual behavior and population ecology: the potential for habitat-dependent population regulation in a reef fish

We used the predictions of the ideal free and ideal despotic distributions (IFD and IDD, respectively) as a basis to evaluate the link between spatial heterogeneity, behavior, and population dynamics in a Caribbean coral reef fish. Juvenile three-spot damselfish (Stegastes planifrons) were more closely aggregated in patch reef habitat than on continuous back reef. Agonistic interactions were more frequent but feeding rates were lower in the patch versus the continuous reef habitat. Growth rates were lower in patch reef habitat than on the continuous reef, but mortality rates did not differ. A separate experiment using standard habitat units demonstrated that the patterns observed in natural habitat were the result of the spatial distribution of the habitat patches rather than resource differences between habitats. Our results do not follow the predictions of simple IFD or IDD models. This deviation from IFD and IDD predictions may be the result of a number of factors, including lack of perfect information about habitat patches, high movement costs, and higher encounter rates of dispersed patches. Our results demonstrate that behavioral interactions are an integral part of population dynamics and that it is necessary to consider the spatial organization of the habitat in both behavioral and ecological investigations. Key words: damselfish, habitat structure, ideal free distribution, recruitment, Stegastes planifrons. [Behav Ecol 11:565–571 (2000)]

Effects of a predatory fish on the recruitment and abundance of Caribbean coral reef fishes

The importance of postrecru~tment factors in determining assemblage structure of coral reef f~shes is one of the most controversial toplcs In community ecology. To document the effects of predat~on on postlarval recruitment and the abundance of resident reef flshes, I manlpulateti small plscivorous fish on 12 model patch reefs located in uniform seagrass habitat in the U S. Virgln Islands. SIX reefs served as controls and 6 were used for predator removals. Weekly censuses were conducted for 2 mo before and after predator manlpulatlons to document effects of removals. Remo\.dls of the squ~l-relfish Holocentrus ddscens~onls had a signlflcant effect on the recruitment and abundance of othelspecles. During the first renloval expenment, which was conducted during a peak recruitment perlod, hlgh densities of squirrelfish depressed postlar\.dl recruitment and juvenile dhundance of grunts Haemulon spp.. the most abundant species on the reefs. Following peak recruitmc.nt of grunts, a second squirrelf~sh removal resulted in increases in juvenile grunt abundance on predator-removal reefs. These results indlcate the importance of postrecruitment factors, particularly predation, in structuring assemblages of coral reef fishes at a small spatial scale.