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About 11 million marine ornamental fish of ca 1800 non-native species are imported into the USA each year. Selecting species for risk assessment is daunting for such a diverse pathway. Herein, we discuss a focused method for species selection: choosing important taxa related to known invaders in high-volume pathways and narrowing prospective species lists to manageable groups of potential hazards. We provide an example using 11 damselfishes, a family with high volume in trade and one of the species established in USA waters. We used a specialized literature review and a risk screening tool (Aquatic Species Invasiveness Screening Kit) to provide an estimate of risk of invasiveness of marine waters of Florida. The established species was identified as a hazard and potential invasive. All other species scored well below the threshold for invasiveness and future climate had little effect on estimates of invasiveness. The analysis revealed little need for additional risk assessment or prohibitions on damselfishes in trade. Education, monitoring, and early detection and rapid response were the main risk management recommendations. The focused species selection process employed herein provided hazard identification and preliminary risk estimates for just 11 species, but collectively, they represent 40% by volume of fishes imported in the marine ornamental trade.

Photoperiod plays a role in controlling the initiation and termination of reproduction in fish. Melatonin is an internal transducer of environmental photoperiod and is involved in regulating reproduction. The present study aimed to examine how melatonin impacts the transcript levels of kisspeptin ( kiss1 and kiss2 ), gonadotropin-releasing hormones ( gnrh1 ), and the β -subunit of gonadotropins ( fshβ and lhβ ) in the brain of the sapphire devil, a tropical damselfish with long photoperiod preference. Feeding mature females with melatonin-containing pellets inhibited increases in the transcript levels of kiss1 , gnrh1 , and lhβ within 3 h. Continuous melatonin treatment for 1 week resulted in oocyte regression and downregulation of kiss2 , gnrh1 , fshβ , and lhβ . When the transcript levels of kiss1 and gnrh1 were measured at 4-h intervals in the brain of sapphire devil, a day–low/night–high fluctuation was observed. The hypothalamic– pituitary–gonadal (HPG) axis may be influenced by melatonin, exerting a negative effect at night because the transcript levels of aralkylamine N -acetyltransferase ( aanat2 ) increased during the scotophase. The expression of aanat2 was higher under short-day than long-day conditions, suggesting that there is a seasonal change in melatonin levels at night. It was concluded that change in photoperiod becomes a proximal factor for controlling the hormone synthesis in the HPG axis through melatonin.

Shoaling behaviour is commonly displayed by fishes and is thought to reduce predation and increase foraging efficiency. Shoaling relies on coordination between individuals, with higher cohesion and alignment among individuals within a shoal providing greater net benefits of this behaviour. Whilst single species often shoal together in conspecific groups, mixed-species shoaling is frequently observed and has been identified as an important determinant of individual fitness for the multiple species involved. Despite their prevalence, the structure of mixed-species shoals and the mechanisms by which individuals gain protection from predators and enhance their foraging efficiency are not as well understood as for single-species shoals. In fact, mixed-species shoals may be less coordinated than single-species shoals, raising the intriguing question of why fishes form mixed-species shoals when this behaviour could be less beneficial than single-species shoaling. Here we used in situ stereo-video techniques to compare within and between shoal differences in cohesion and alignment, for mixed- and single-species shoals containing the tropical vagrant Indo pacific sergeant major damselfish, Abudefduf vaigiensis, in temperate waters. As expected, mixed-species shoals were less aligned than single-species shoals. However, within mixed-species shoals conspecifics were more cohesive and aligned than were heterospecifics, suggesting coordinated single-species subgroups formed within larger mixed-species shoals. The formation of subgroups may mitigate costs associated with differences between species, therefore enhancing benefits of mixed-species shoaling. As such, multiple levels of social structure may exist within mixed-species shoals that could facilitate growth and survival for vagrant A. vaigiensis in temperate regions. More broadly, this research highlights the importance of considering detailed internal structures of mixed-species shoals when trying to understand cost–benefit trade-offs experienced by individuals.

Widespread coral mortality is leading to coral reef degradation worldwide. Many juvenile reef fishes settle on live coral, and their predator-avoidance behaviour is disrupted in seawater exposed to dead corals, ultimately increasing predation risk. Gnathiid isopods are micropredatory fish ectoparasites that occur in higher abundances in dead coral. However, the effect of seawater associated with dead coral on the susceptibility of fish to micropredators has never been investigated. We tested whether the infection rate of cultured gnathiid ectoparasites on individual damselfish, Pomacentrus amboinensis Bleeker 1868, from two different ontogenetic stages (juveniles and adults) was influenced by seawater exposed to three different treatments: dead coral, live coral, or no coral. Seawater treatments were presumed to contain different chemical properties and are meant to represent environmental changes associated with habitat degradation on coral reefs. Gnathiid infection of juvenile fish in seawater exposed to dead coral was twice as high as that of fish in live coral or no coral. Infection rates did not significantly differ between live coral and no coral treatments. In contrast to juveniles, the susceptibility of adults to gnathiids was not affected by seawater treatment. During experiments, juvenile fish mortality was relatively low, but was higher for infected fish (9.7%), compared to fish held without exposure to gnathiids (1.7%). No mortality occurred in adult fish that became infected with gnathiids. Our results suggest that chemical cues released from dead corals and/or dead coral colonisers affect the ability of juvenile, but not adult fish to avoid parasite infection. Considering increased habitat degradation on coral reefs and that gnathiids are more abundant in dead coral substrate, it is possible that wild juvenile fish may experience increased susceptibility to parasitic infection and reduced survival rate. This highlights the importance of including parasitism in ecological studies of global environmental change.

Changes in fish communities as oceans warm and cool and competition for space between established and novel species can be evaluated in biogeographic transition zones such as the west coast of Australia. At ~30° S in this region, a cool anomaly occurred in the 2000s, between marine heatwaves. Over 2 yr of that anomaly, surveyed reef fishes were 57% temperate, 18% sub-tropical and 25% tropical. The most numerous fishes included a wrasse, herring, bullseye, drummer and damselfish. Based on similarities in the composition of fishes, 7 significant clusters of reefs were identified along a gradation from deep, exposed reefs to shallow, protected lagoonal reefs. Endemic sub-tropical and temperate wrasses and damselfishes typified all reefs. Some of these were ubiquitous over exposed and lagoonal reefs and others prevalent in only one reef type, demonstrating habitat preferences and partitioning among closely related species. This was reflected in the differing order of importance of fishes that typified different reefs. Linear modelling indicated that abiotic (depth, distance from shore) and biotic factors (e.g. algae) explained most of the variation in the fish communities among reefs. Additional variation, particularly within lagoonal reefs, was related to relief, turf and corals, rather than water temperature. Occurrence and reproductive activity of a group of tropical/sub-tropical wrasses and damselfish in some lagoonal reefs with abundant tropical habitats (e.g. corals) suggested that they supported novel communities during cool anomalies. Better predictions of future change and interactions between existing and novel species with environmental cycles requires knowledge of species-specific habitat relationships and biology.

Damselfish of the genus Stegastes inhabit territories and cultivate algal gardens on branching corals of the genus Acropora, aggressively protecting their territories from other fish and preventing predation upon corals within the territory. This behaviour has important ecological impacts and could also be useful in reducing predation on outplanted corals during reef restoration efforts. However, the degree of protection from predators may depend on the ability of Stegastes spp. to recolonise outplanted or newly established coral colonies. Protection of bleaching-resilient massive corals within territories may be of particular importance due to the role of these corals in maintaining coral cover following bleaching events. This study examined whether the presence of Stegastes spp. reduces predation on the massive bleaching-resilient coral Porites lutea in the Mauritian lagoon, and whether Stegastes spp. readily colonise outplanted branching coral fragments and provide adjacent massive corals with indirect protection from predation. Predation levels on wild-occurring and outplanted P. lutea within and outside Stegastes spp. territories were measured. In addition, Acropora muricata branches were outplanted adjacent to wild P. lutea colonies outside Stegastes spp. territories, and recolonisation of these outplants by Stegastes spp. and the impacts of recolonisation on predation were monitored. Both wild and outplanted P. lutea colonies within Stegastes spp. territories sustained less predation damage compared to colonies outside territories. Stegastes spp. recolonized outplanted A. muricata colonies within six months of outplanting, and in doing so returned predation protection to adjacent P. lutea colonies. The ability of Stegastes spp. to colonise outplanted corals and provide indirect protection to adjacent massive bleaching-resilient corals may inform coral outplanting efforts in systems where Stegastes spp. are common. Encouraging Stegastes spp. recolonisation may help to reduce predation damage to corals within territories and potentially improve the success of rehabilitation efforts.

Cyclones have one of the greatest effects on the biodiversity of coral reefs and the associated species. But it is unknown how stochastic alterations in habitat structure influence metapopulation structure, connectivity and genetic diversity. From 1993 to 2018, the reefs of the Capricorn Bunker Reef group in the southern part of the Great Barrier Reef were impacted by three tropical cyclones including cyclone Hamish (2009, category 5). This resulted in substantial loss of live habitat-forming coral and coral reef fish communities. Within 6–8 years after cyclones had devastated, live hard corals recovered by 50–60%. We show the relationship between hard coral cover and the abundance of the neon damselfish (Pomacentrus coelestis), the first fish colonizing destroyed reefs. We present the first long-term (2008–2015 years corresponding to 16–24 generations of P. coelestis) population genetic study to understand the impact of cyclones on the meta-population structure, connectivity and genetic diversity of the neon damselfish. After the cyclone, we observed the largest change in the genetic structure at reef populations compared to other years. Simultaneously, allelic richness of genetic microsatellite markers dropped indicating a great loss of genetic diversity, which increased again in subsequent years. Over years, metapopulation dynamics were characterized by high connectivity among fish populations associated with the Capricorn Bunker reefs (2200 km2); however, despite high exchange, genetic patchiness was observed with annual strong genetic divergence between populations among reefs. Some broad similarities in the genetic structure in 2015 could be explained by dispersal from a source reef and the related expansion of local populations. This study has shown that alternating cyclone-driven changes and subsequent recovery phases of coral habitat can greatly influence patterns of reef fish connectivity. The frequency of disturbances determines abundance of fish and genetic diversity within species.

In coral reef communities, sea urchins and reef fish have a variety of commensal relationships. However, if fish view urchins as a potential form of predator protection, then urchin presence should influence reef fish risk assessment. We investigated whether dusky damselfish (Stegastes nigricans) perceive burrowing urchins (Echinometra mathaei) as a form of predator protection by asking whether and how urchin presence explains variation in flight initiation distance, the distance a fish fled an approaching threat. We found that when individuals were subjected to a high-risk approach (i.e., one that started relatively close to the fish), and urchin density was high, dusky damselfish tolerated a closer approach than when subjected to high risk with low urchin density. However, when there was low risk and high urchin density, the damselfish fled sooner. We conclude that under high risk, damselfish perceive burrowing urchins as providing added security from approaching threats.

La última valoración sobre la extensión, estado y cobertura viva (%) de las formaciones de Acropora palmata (29) y A. cervicornis (12) en el Parque Nacional Natural Tayrona fue realizada en 2001 y publicada en 2004. Estas mismas formaciones, incluyendo una adicional en isla Aguja, fueron evaluadas de nuevo entre 2016 y 2018 teniendo en cuenta las mismas variables, y adicionalmente el registro de condición de las colonias. Para A. palmata se encontraron 24 formaciones con una reducción en área de 28,9 %. La cobertura promedio aumentó cerca de 2,0 %, y se observó una amplia distribución de frecuencia de tallas y una proporción importante de colonias con territorios de peces damisela (Stegastes). El área de las formaciones de A. cervicornis se redujo 99,3 % y solo se encontró una formación en Nenguange, aunque se registran dos nuevas y pequeñas en Cinto y otra en Chengue. La cobertura promedio fue de 8,0 %, en su mayoría constituida por colonias de talla pequeña y principalmente afectadas por blanqueamiento, macroalgas, enfermedades y depredadores. Claramente el estatus de las dos especies es diferente por lo que requieren esfuerzos diferentes para su manejo y conservación. Las formaciones de A. palmata han persistido, pero es necesario realizar estudios continuos que permitan detectar cambios temporales, con evaluaciones de aspectos ecológicos como las afectaciones por los peces damisela. El estado de A. cerviconis es crítico, por lo que demanda acciones urgentes de restauración y otras medidas de manejo para mitigar la tendencia a su desaparición en el área.

Corals from the Gulf of Aqaba (northern Red Sea) are resilient to high temperatures and therefore this region is regarded as globally important for reef conservation. However, long-term dynamics of coral reef assemblages from the Gulf of Aqaba remain largely understudied. In this study, we analysed the change in benthic, fish and invertebrate assemblages of reefs around Dahab (South Sinai, Egypt) between 2009 and 2019. We also studied the individual trajectories of coral reef benthic categories, key invertebrate and fish species and their relationship. As site emerged as the main factor explaining the variability in coral reef communities, we identified three clusters of sites with similar assemblages. Both benthic, fish and invertebrate assemblages changed considerably at the three site clusters between 2009 and 2019. We found significant increases in fleshy macroalgae (~ 6 to 15%) and cyanobacterial mats (~ 6 to 12%) in all site clusters. Although not observing a significant reduction of hard coral cover, both macroalgae mat cover and cyanobacterial mat cover were significantly negatively related to hard coral cover and hard coral disease. Soft coral cover (mainly corals from the Xeniidae family) decreased significantly in two of the site clusters, their cover being negatively related to macroalgal and cyanobacterial cover. Significant declines in grazer urchins were observed at all site clusters, and a strong negative relationship was found with macroalgae and cyanobacterial mats cover, suggesting urchin decline as one of the main drivers behind algal increases. Different site clusters had different fish trajectories (butterflyfish, parrotfish, surgeonfish and predators), with only damselfish densities significantly decreasing at all sites. A significant decrease in damselfish densities was related to increases in cyanobacterial mats. These findings suggest that if macroalgae and cyanobacteria continue to increase, Dahab coral reefs could undergo degradation, and therefore, more studies are needed to elucidate the drivers behind these algal increases.

Dusky damselfish (Stegastes fuscus) behaviour was investigated under natural and controlled conditions to evaluate how territory and familiarity affect aggressive behaviour. In the natural environment, fish occupies territories of 2.74 ± 1.3 m2 and the most frequent behaviours exhibited were monitoring swimming, feeding, shelter occupation and agonistic interactions. Larger-territory individuals spend more time in monitoring swimming than smaller-territory ones, which results in a reduction of food intake. Agonistic interactions were more frequent with heterospecifics than conspecifics. Whenever agonistic interaction occurred, confrontations were not frequent. Territorial behaviour in the lab was evaluated considering two variables: prior residence and familiarity between conspecific opponents. Resident fish invested more against intruders irrespective of the intruder’s identity (familiar or unfamiliar). When no previous territory was established, S. fuscus showed lower aggressive behaviour, and it was even lower when a familiar fish was the opponent. Data from the field and the lab suggest that S. fuscus territoriality and aggression are related to the size of the defended area and the competitor’s identity. Thus, reduced reef areas may result in increased interindividual aggression, while the intruders’ recognition may be a key trait controlling agonistic behaviour in the reef community where S. fuscus is inserted.

Acropora provides an example of reef degradation, as evidenced by population reductions in Caribbean reefs. However, data on the current status of Acropora populations in Colombia are lacking. In this study, reef habitats were surveyed for Acropora palmata and Acropora cervicornis throughout the Colombian Caribbean, and the size structure, coverage and colony conditions of their populations were evaluated. Acropora palmata size classes were negatively skewed, indicating low recruitment. This species exhibited a patch-type distribution around Tayrona, Isla Fuerte and Isla Arena; these localities exhibited the highest cover among the surveyed regions. The lowest coral cover was recorded for the Rosario Islands. Healthy colonies were dominant; however, disease and damselfish territories were common. The size class data of Acropora cervicornis indicated the persistence of small colonies; however, no recruits were observed. The distribution was dispersed, with important patches and the highest cover observed around the Uraba Gulf and Rosario Islands. Overall, the cover was lower than 10%. Few healthy colonies were observed, and macroalgae and sponges were common. Conservation and management efforts are required for both species; for Acropora palmata, efforts targeting the Rosario Islands are needed, whereas Acropora cervicornis is in critical condition throughout the Colombian Caribbean.

The detrimental effects of invasion by Indo-Pacific lionfish Pterois volitans/miles on western Atlantic fishes have spurred concerns for Mediterranean fish biodiversity, where Lessepsian lionfish P. miles have recently established populations in the eastern basin. In order to assess the potential impact on biodiversity, we examined key behavioural and ecological traits of lionfish and the resident fish community in the Mediterranean that may contribute to lionfish invasion success. We focussed on Cyprus, where lionfish were first sighted in 2012 and have now formed abundant and stable populations. Using field observations, we examined lionfish predatory behaviour and feeding ecology, and naiveté of resident fish species to hunting lionfish. Our findings suggest that lionfish in the Mediterranean are crepuscular generalist predators, with targeted prey dominated by small-bodied benthic or bentho-pelagic associated species. Such prey are more likely to be native than introduced (Lessepsian) fishes, with native prey fishes showing greater naiveté towards lionfish than Lessepsian prey species. Notably, one of the Mediterranean’s key ecological fish species (the native damselfish Chromis chromis) showed the highest level of naiveté and was the most heavily targeted prey. Overall, lionfish in the Mediterranean show similar predatory behaviour and ecology to their western Atlantic counterparts. Although the establishment of Mediterranean lionfish populations is still recent, it may result in a similar disruption to reef fish biomass to that recorded in the Atlantic, with impacts on the structure and biodiversity of reef fish communities and the services they provide.

The longevity-homeoviscous adaptation (LHA) theory of ageing states that lipid composition of cell membranes is linked to metabolic rate and lifespan, which has been widely shown in mammals and birds but not sufficiently in fish. In this study, two species of the genus Amphiprion (Amphiprion percula and Amphiprion clarkii, with estimated maximum lifespan potentials [MLSP] of 30 and 9–16 years, respectively) and the damselfish Chromis viridis (estimated MLSP of 1–2 years) were chosen to test the LHA theory of ageing in a potential model of exceptional longevity. Brain, livers and samples of skeletal muscle were collected for lipid analyses and integral part in the computation of membrane peroxidation indexes (PIn) from phospholipid (PL) fractions and PL fatty acid composition. When only the two Amphiprion species were compared, results pointed to the existence of a negative correlation between membrane PIn value and maximum lifespan, well in line with the predictions from the LHA theory of ageing. Nevertheless, contradictory data were obtained when the two Amphiprion species were compared to the shorter-lived C. viridis. These results along with those obtained in previous studies on fish denote that the magnitude (and sometimes the direction) of the differences observed in membrane lipid composition and peroxidation index with MLSP cannot explain alone the diversity in longevity found among fishes.

Over small spatial scales, coral reefs represent a mosaic of suitable settlement microhabitat patches of varying size for late-stage larval reef fishes. Few studies have specifically examined how variation in patch size influences density of recently settled coral reef fishes (recruits). Using standardized units of coral rubble settlement substrate deployed on sandy bottom, we monitored the concurrent settlement of three reef fish taxa onto differently sized patches (0.28–1.68 m2) at 5-d intervals during a lunar settlement peak. We found marked differences among taxa in how recruit density scaled with patch size. Recruit density of a damselfish and a parrotfish decreased and increased, respectively, with the increase in patch size, while that of a wrasse was similar among patch sizes. Our results highlight the importance of the interaction between taxon-specific settlement behaviour and patch size in establishing initial spatial differences in density within and among coral reef fish taxa in a heterogeneous landscape.

Many coral reef fishes are intimately associated with branching corals. While these fishes rely on their host corals for shelter, fishes may exhibit behavioral trade-offs linked to spatial and temporal variations in their association with corals. This study quantified variation in coral use by 5 species of damselfishes, assessing key behavioral traits that determine the extent to which damselfishes interact with their host colonies. In situ behavioral observations revealed marked interspecific differences in diurnal and nocturnal behavior among 5 damselfish species. Dascyllus aruanus and D. reticulatus consistently displayed frequent and sustained interactions with and around corals (i.e. frequent colony visits and high aggressiveness towards other fishes) compared to Chromis viridis, Pomacentrus moluccensis, and P. amboinensis that exhibited weaker associa- tions (i.e. few colony visits and low aggression) with host colonies. Coral bleaching impacted modal diurnal swimming positions, thereby altering damselfish−coral interactions under thermal stress. This research demonstrates that coral-associated damselfishes utilize host colonies in very different ways, with complex variations in behavior that extend beyond simple proximity to host coral. Such among-species variation is likely the result of behavioral trade-offs related to coral association. Understanding species-specific foraging and colony-use behavior is important be- cause habitat degradation may undermine habitat associations of coral−damselfish and associated mutualistic services.

Response of orange-finned anemonefish Amphiprion chrysopterus and three-spot damselfish Dascyllus trimaculatus to red laser-pointer light was studied in Mo'orea, French Polynesia. Four magnificent anemones Heteractis magnifica and their resident fish were observed for typical behaviours (biting, chasing, hiding, posing, lunging and retreating) with and without exposure to laser-pointer light. Lunging behaviour increased significantly for both fish species upon exposure to laser-pointer light; none of the other behaviours changed significantly. We advance the hypothesis that orange-finned anemonefish and three-spot damselfish interpret laser pointer stimulation as a territorial threat.

Planktivorous fishes are known to consume coral larvae due to their high nutritional value that can benefit both the individual and their progeny. However, how the consumption of coral larvae varies among coral and fish taxa, between day and night and with the density of coral larvae is not well understood. Here, we used a series of laboratory feeding assays to determine how the consumption of coral larvae by five planktivorous damselfish species (Abudefduf sexfasciatus, Amblyglyphidodon curacao, Dascyllus trimaculatus, D. reticulatus, and Chromis viridis) differed (1) between larvae of the broadcast-spawning scleractinian coral Acropora tenuis and the brooding non-scleractinian coral Heliopora coerulea when offered at a constant density (100 larvae/50 L), (2) between day and night (A. tenuis only), and (3) among larval densities (A. tenuis: 5–500 larvae/50 L; H. coerulea: 5–250 larvae/50 L). When coral larvae were offered at 100 larvae/50 L, all five fish species examined consumed A. tenuis (78–97 larvae h−1) at a greater rate than H. coerulea (23–57 larvae h−1), with these differences likely related to the behavior and/or pigmentation of the larvae. Consumption also varied among the fishes examined, though the differences were small when compared to differences between coral species. Consumption of A. tenuis was twofold higher at day than night likely reflecting the diurnally active feeding behavior of the fishes examined. When the density of coral larvae offered to the fishes was varied, three of five species exhibited a type II functional response (decelerating intake rate) for A. tenuis, while four out of five damselfish species exhibited a type III (sigmoidal intake rate) or type I (linear intake rate) for H. coerulea. This study demonstrates that predation by fishes contributes significantly to coral larvae mortality and that differences in consumption rates among coral species may affect the composition of coral recruits and ultimately coral assemblages.

Herbivorous damselfish that cultivate algal farms frequently exhibit aggressive territorial behaviour to defend their investment from intruders, particularly against other herbivorous fish and invertebrates. On a coastal coral reef in New Caledonia, the response of the damselfish Hemiglyphidodon plagiometopon to intruders of varying type and level of threat to their algal farm was tested. Responses to live and dead coral fragments, carnivorous whelks, shells, and rocks varied from no response to biting and extrusion from farms. Damselfish elicited the strongest defensive response to the herbivorous sea urchin Echinometra mathaei, rapidly attacking the urchin by biting and lifting it from farms, before extruding it up to 3.5 m away. H. plagiometopon responded in a similar manner to dead urchins (no threat of herbivory) as to live urchins, but typically did not extrude them as far. Ultimately, damselfish responded to intruders in a manner largely consistent with the level of threat posed to their algal farm, with the similar response between live and dead urchins suggesting such strong defensive behaviours may be combination of ‘hard-wired’ and learned behaviours in reaction to the level of realised threat.

Despite increasing environmental variability within marine ecosystems, little is known about how coral reef fish species will cope with future climate scenarios. The Arabian/Persian Gulf is an extreme environment, providing an opportunity to study fish behaviour on reefs with seasonal temperature ranges which include both values above the mortality threshold of Indo-Pacific reef fish, and values below the optimum temperature for growth. Summer temperatures in the Gulf are comparable to those predicted for the tropical ocean by 2090–2099. Using field observations in winter, spring and summer, and laboratory experiments, we examined the foraging activity, distance from refugia and resting time of Pomacentrus trichrourus (pale-tail damselfish). Observations of fish behaviour in natural conditions showed that individuals substantially reduced distance from refugia and feeding rate and increased resting time at sub-optimal environmental temperatures in winter (average SST = 21 °C) and summer (average SST = 34 °C), while showing high movement and feeding activity in spring (average SST = 27 °C). Diet was dominated by plankton in winter and spring, while fish used both plankton and benthic trophic resources in summer. These findings were corroborated under laboratory conditions: in a replicated aquarium experiment, time away from refugia and activity were significantly higher at 28 °C (i.e. spring temperature conditions) compared to 21 °C (i.e. winter temperature conditions). Our findings suggest that P. trichrourus may have adapted to the Arabian/Persian Gulf environment by downregulating costly activity during winter and summer and upregulating activity and increasing energy stores in spring. Such adaptive behavioural plasticity may be an important factor in the persistence of populations within increasing environmentally variable coral reef ecosystems.

Habitat characteristics play an important role in determining the structure of fish communities. The decline in fish diversity and abundance with the decline in coral diversity and cover may be explained by habitat specialisation and partitioning among reef fishes and/or preferences for particular corals that are susceptible to disturbance. These preferences may develop at different life history stages. Here, we investigated patterns of habitat specialisation and ontogenetic shifts in habitat preference among 14 co-existing damselfish species at Lizard Island lagoon on the Great Barrier Reef. Although live coral cover contributed only 26% of the substratum, 28% of adults and 57% of new settlers were mostly found on live coral, indicating a strong preference for live coral habitat by new settlers. Only a few species exhibited a high degree of habitat specialisation and low overlap in habitat use with other species. Specialisation differed among species and life stages. New settlers were more commonly associated with finely branched corymbose corals and using those habitats with higher frequency than expected based on habitat availability alone. Adults were more commonly linked to more open branching morphologies or non-coral substrata. Our results suggest that habitat loss may not uniformly impact on all life stages. While adult individuals may not be as reliant as juveniles on corals, detrimental effects of habitat loss on juvenile survival may have longer-term impacts on adult populations. As juveniles show preferential associations with particular coral species, such as corymbose corals, the loss of these growth forms is likely to have the most significant negative impacts on this critical life history stage.

Coral reefs are highly productive ecosystems that typically exist in nutrient-poor waters, stimulating considerable research on the sources of nutrients that may support this productivity, including nutrient recycling. We examined the potential for resident herbivorous damselfish ( Stegastes nigricans ) to recycle nutrients within their territories by conducting an exclusion experiment on S. nigricans territories and measuring algal turf growth on shallow fringing reefs in Mo'orea, French Polynesia. A nutrient bioassay was used to evaluate whether the enhanced growth was due to increased nutrients. We chose 15 isolated damselfish territories for a caging experiment, with a large cage obstructing all fish access on one half of the territory (−Damselfish, −Herbivory) and a small low-profile cage allowing access but not herbivory to a portion on the other half (+Damselfish −Herbivory). Additionally, we measured turf in a randomly-chosen uncaged area within each territory where both damselfish and herbivory were present (+Damselfish +Herbivory). Behavioral observations confirmed damselfish rarely swam over the large-caged half of the territory, effectively eliminating their physical presence, but continued to interact with the other half. Over the 16-day experiment, time and treatment had a significant effect on turf growth. By day 16, the turf receiving the +Damselfish −Herbivory treatment experienced average net turf growth of 5.34 mm, which was significantly greater than turf growth within the territories receiving the −Damselfish −Herbivory (2.13 mm) and the +Damselfish +Herbivory (1.50 mm) treatments. The macroalgae in the nutrient bioassay grew 21% more on the side of the territory where damselfish were present compared to the side where they were excluded, supporting our conclusion that the mechanism that supported faster turf growth was increased nutrients. Thus, our study was the first to establish experimentally that the presence of damselfish increased algal growth by enhancing nutrient supplies via recycled waste products, a mechanism that has been advanced but never tested. Surveys established that damselfish territories covered 28–64% of the fringing reef flat along the north shore of Mo'orea, suggesting this increased productivity within territories could be a significant contribution to total reef productivity. These findings highlight the importance of continuing research into the long-term and spatial-scale effects of damselfish as nutrient recyclers on coral reefs.

The large caerulean damselfish, Pomacentrus caeruleopunctatus Allen, 2002, is recorded for the first time from Reunion Island. Two individuals were observed and photographed between January and March 2012 on L’Hermitage reef, located on the west coast of the island. A review of high-resolution profile photographs of these two individuals shows that their external morphological characteristics agree well with those reported in the original description of the species. These observations suggest an extension of the known distribution of the species, previously restricted to the Seychelles Islands, Madagascar, and Tanzania, to the Mascarene Archipelago, and moreover the known depth range of this species.

The present study investigates how the humbug damselfish Dascyllus aruanus, subject of a large number of ecological, evolutionary and behavioural studies, responds to the presence of human observers (effect of scuba diver presence-absence) and how the method of data collection (directly by a scuba diver v. indirectly via video camera) may affect the quality of behavioural data. Scuba diver presence had only subtle effects on fish behaviour. The efficiency of the method of scoring fish behaviour depended on the behaviour under consideration: those behaviours that occur in close proximity to the corals were scored more effectively directly by a scuba diver while those that are performed in a more rapid or repetitive fashion were scored more effectively indirectly via video camera. These results provide a foundation for future behavioural research on D. aruanus and other fishes where scuba divers or video cameras are the prevalent means of data collection.

A 6-week laboratory experiment exposed juvenile Ambon damselfish Pomacentrus amboinensis to visual and chemical cues of either a predator, a herbivore or a null control (sea water) and found no effect of predator cues on prey morphology (proportion of ocellus to eye diameter, body depth, standard length and fin area). Nonetheless, behaviour was significantly affected by predator presence, with prey less active and taking half as many feeding strikes when exposed to predators compared to fish from the null control. The presence of a herbivore also affected prey behaviour similar to that of the predator, suggesting that the presence of a non-predator may have important effects on development.

In marine organisms, pelagic larval dispersal often results in genetic panmixis among widely separated populations; however, local conditions may produce populations of marine organisms that differ in key life history traits. Here, we assess spatial differences in growth, body condition, survivorship and movement over a decade for lemon damselfish Pomacentrus moluccensis. Newly recruited fish were tagged on the southern (One Tree Island, 23°S), and northern Great Barrier Reef (Lizard Island, 15°S), 1200 km apart, and monitored for over a decade to provide direct data on growth and survivorship. New recruit physiological condition (lipid content) had a weak positive influence on early survival, but not on long-term persistence or growth, and the larval supply signal was lost after 2 years, suggesting post-settlement processes were key in long-term population persistence. Fish exhibited extreme site fidelity, with older/larger fish moving most (all less than 7 m). At Lizard Island, under 5% of individuals remained after 3 years, none after 4 years, while at One Tree Island 5% of individuals survived over 5 years, with 1% remaining after a decade, suggesting Lizard Island populations may require more frequent replenishment to persist. Among-site (within location) variation in mortality was high, and not related to density, suggesting local conditions such as wave exposure and predators were important. Surprisingly, mean growth at the two locations, which differ by around 2 °C on average in sea temperature, was practically identical, levelling off after 3 years, but with high variation among nearby sites within each location, which would affect size-based fecundity and time of first reproduction at these smaller spatial scales. Neither early post-settlement growth nor mortality were density-dependent, and early growth was not related to overall longevity. These small reef fishes are highly sedentary and some demographic parameters, but not others, differ at a range of scales, with post-settlement populations likely driven largely by mortality patterns at the larger spatial scale. Latitudinal and smaller-spatial scale differences in performance (growth, survival) of this species, leading to offsets in expected time to maturity an fecundity, are contrasted by evidence of stability of adult populations over two decades at One Tree Island, which suggests that resilience to environmental change/climate change and other externalities differ considerably across this species’ distribution.

Streptococcus iniae causes high mortality in cultured and wild fish stocks globally. Since the first report in captive Amazon river dolphins Inia geoffrensis in 1976, it has emerged in finfish across all continents except Antarctica. In March 2016, an estimated 17000 fish were observed dead and dying along a remote 70 km stretch of the Kimberley coastline north of Broome, Western Australia. Affected species included finfish (lionfish Pterois volitans, angelfish Pomacanthus sp., stripey snapper Lutjanus carponotatus, sand bass Psammoperca waigiensis, yellowtail grunter Amniataba caudavittata, damselfish Pomacentridae sp.), flatback sea turtles Natator depressus, and olive (Aipysurus laevis) and black-ringed (Hydrelaps darwiniensis) sea snakes. Moribund fish collected during the event exhibited exophthalmia and abnormal behaviour, such as spiralling on the surface or within the water column. Subsequent histopathological examination of 2 fish species revealed bacterial septicaemia with chains of Gram-positive cocci seen in multiple organs and within brain tissue. S. iniae was isolated and identified by bacterial culture, species-specific PCR, Matrix-Assisted Laser Desorption Ionisation Time-Of-Flight (MALDI-TOF) and biochemical testing. This is the first report of S. iniae associated with a major multi-species wild marine fish kill in Australia. Extreme weather events in the region including a marked decrease in water temperatures, followed by an extended period of above-average coastal water temperatures, were implicated as stressors potentially contributing to this outbreak.

Coral loss is a major element of global ecological change in the oceans that may shape the behavior of keystone species such as habitat-attached animals. Farming damselfishes cultivate and aggressively protect algal garden within their territory, thereby shaping local fish assemblages and macro-algae diversity. Following the widespread loss of live branching coral throughout Florida and the Caribbean Sea, dusky damselfish (Stegastes adustus) have modified their territorial behavior. We compared antagonistic behavior, and size and algal species composition of territories of dusky damselfish on dead branching coral rubble and live boulder coral in the Dry Tortugas National Park, USA. Even though similar numbers of “intruders” entered each habitat type, dusky damselfish on rubble territories chased out significantly more fishes, had larger territories and more species of algae were present in their gardens. This study shows that dusky damselfish successfully occupy living and dead coral areas; however, there are potential trade-offs between defending a larger territory and cultivating fewer algal species.

Elevated CO2 levels predicted to occur by the end of the century can affect the physiology and behaviour of marine fishes. For one important survival mechanism, the response to chemical alarm cues from conspecifics, substantial among-individual variation in the extent of behavioural impairment when exposed to elevated CO2 has been observed in previous studies. Whole brain transcriptomic data has further emphasized the importance of parental phenotypic variation in the response of juvenile fish to elevated CO2. In this study, we investigate the genome-wide proteomic responses of this variation in the brain of 5-week old spiny damselfish, Acanthochromis polyacanthus. We compared the expression of proteins in the brains of juvenile A. polyacanthus from two different parental behavioural phenotypes (sensitive and tolerant) that had been experimentally exposed to short-term, long-term and inter-generational elevated CO2. Our results show differential expression of key proteins related to stress response and epigenetic markers with elevated CO2 exposure. Proteins related to neurological development were also differentially expressed particularly in the long-term developmental treatment, which might be critical for juvenile development. By contrast, exposure to elevated CO2 in the parental generation resulted in only three differentially expressed proteins in the offspring, revealing potential for inter-generational acclimation. Lastly, we found a distinct proteomic pattern in juveniles due to the behavioural sensitivity of parents to elevated CO2, even though the behaviour of the juvenile fish was impaired regardless of parental phenotype. Our data shows that developing juveniles are affected in their brain protein expression by elevated CO2, but the effect varies with the length of exposure as well as due to variation of parental phenotypes in the population.

In many mutualisms, benefits in the form of food are exchanged for services such as transport or protection. In the marine cleaning mutualism, a variety of “client” reef fishes offer “cleaner” fish Labroides dimidiatus access to food in the form of their ectoparasites, where parasite removal supposedly protects the clients. Yet, the health benefits individual clients obtain on the long-term from repeated ectoparasite removal remain relatively unknown. Here, we tested whether long-term reduced access to cleaning services alter indicators of health status such as body condition, immunity and the steroids cortisol and testosterone in four client damselfish species Pomacentrus amboinensis, Amblyglyphidodon curacao, Acanthochromis polyacanthus, and Dischistodus perspicillatus. To do so, we took advantage of a long-term experimental project in which several small reefs around Lizard Island (Great Barrier Reef, Australia) were maintained cleaner-free since the year 2000; while control reefs had their cleaner presence continuously monitored. We found that the four damselfish species from reef sites without cleaners for 13 years had lower body condition than fish from reefs with cleaners. However, immunity measurements and cortisol and testosterone levels did not differ between experimental groups. Our findings suggest that clients use the energetic benefits derived from long-term access to cleaning services to selectively increase body condition, rather than altering hormonal or immune system functions.

Coral reef fishes are known to respond to chemical cues in the selection of appropriate microhabitats at settlement. Coral- and non-coral-associated species are likely to respond to different stimuli and the cues may change as larvae settle and become familiar with the reef environment. Here, the chemosensory responses of both late-stage larvae and newly settled juvenile damselfishes to microhabitat odours were tested in Kimbe Bay (PNG), including four obligate coral-dwelling species (Dascyllus melanurus, D. reticulatus, Chrysiptera arnazae and Pomacentrus moluccensis) and four rubble-dwelling species (Pomacentrus adelus, P. simsiang, Chrysiptera cyanea and C. rollandi). Damselfishes were subjected to a series of pair-wise chemosensory choice trials using a two-channel choice flume. The responses by late-stage larvae (pre-settled) to chemical cues from their preferred microhabitat type mirrored those exhibited by recently settled juveniles. All four rubble-dwelling damselfish species exhibited a significant aversion toward chemical cues derived from coral microhabitats, preferring to remain either in the water seeded with chemical cues derived from rubble, or the unseeded (control) water. The obligate coral-dwelling damselfish species tended to avoid rubble and select coral cues when tested against seawater, but unexpectedly, exhibited a neutral response when given a choice between coral and rubble odours. These results indicate that coral and rubble-dwelling damselfish differ in the strength of their attraction to preferred or avoidance of non-preferred microhabitats. Both factors are likely to play a role in settlement choices. Our results indicated that for some species, newly settled juveniles could act as suitable substitutes for testing larval behavioural traits.

Many “client” coral reef fishes have their ectoparasites removed by the “cleaner” wrasse Labroides dimidiatus in mutualistic interactions. Clients regularly receiving cleaning services reportedly benefit from increased growth and cognitive performance, but the underlying physiological changes that covary with such benefits are unknown. Here, we tested whether reduced access to cleaning services affects physiological state in two species of damselfish, Amblyglyphidodon curacao and Acanthochromis polyacanthus. We performed an in situ removal experiment on the Great Barrier Reef, Australia, whereby 47% of cleaners on a natural reef were removed. Since cleaners occupy defined territories (called “cleaning stations”), this removal created areas where small, resident clients, including A. polyacanthus and A. amblyglyphidodon, had no access to cleaning services. One month following cleaner removal, we measured body condition and collected blood samples from both damselfish species from territories with and without access to cleaners. Blood was used for estimating haematocrit levels, hormonal analyses, and immune cell counts. We tested for correlations among all these parameters to explore potential trade-offs in terms of growth, aerobic capacity, immune activation, and/or reproduction as a result of the loss of cleaning benefits. In both species, we found that fish without access to cleaners had lower haematocrit, testosterone levels, and lymphocyte counts than fish with access. There were no significant changes in fish body condition, leukocytes, granulocytes, or plasma cortisol levels between fish with access to cleaners or not. However, testosterone levels correlated negatively with the proportion of granulocytes in the blood of fish with access to cleaners. Our results suggest that even a relatively short-term reduction in access to cleaning services can have negative physiological outcomes for clients. Thus, the presence of cleaners on coral reefs appears to have important benefits for coral reef fish community health.

Aggression and territory size of the farmer damselfish Plectroglyphidodon lacrymatus were examined in the presence of adjacent territories of conspecific and heterospecific farmers that maintain algal turf territories on the reefs of Anda, north-western Philippines. Plectroglyphidodon lacrymatus territories with no adjacent neighbours had a mean size of 1.2 m2 whereas those adjacent to conspecifics were 47% smaller. In contrast, the mean size of territories adjacent to a heterospecific farmer (i.e., Pomacentrus burroughi, Pomacentrus chrysurus) did not differ from that of solitary individuals. Aggression towards conspecific farmers (84% probability) was higher than heterospecific farmers (31%). The higher aggression towards conspecific farmers suggests that the energetic costs for defence increased, which may have caused a decrease in territory sizes. Despite the higher aggression towards conspecific farmers, the thickness and percentage cover of algae inside the territories of focal fish did not appear to vary according to type of neighbouring farmer although algal turf cover was higher and juvenile coral occurrence was lower inside than outside the territories. Our results show that the territorial behaviour of P. lacrymatus varies with conspecific and heterospecific farmers, which may influence their distribution and benthic habitat characteristics.

Roving herbivorous fishes play an important role in coral reef communities by removing turf-algae, which can facilitate the settlement of coral larvae. Territorial damselfishes can influence the foraging patterns of roving herbivores by excluding them from their territories, altering the benthic assemblage. However, the impacts depend on the intensity of aggression and which taxonomic groups of roving herbivores are being excluded. Here we document the foraging activity of roving herbivores (Acanthuridae, Scaridae, Siganidae) and the extent to which they are subject to aggression by Pomacentrus adelus, the most abundant territorial damselfish in Kimbe Bay, Papua New Guinea. We then conducted experimental removals (220 m2 plots on the reef flat) of P. adelus to examine its impact on roving herbivores and the benthic community structure. We hypothesized that the removal of P. adelus would lead to an increase in roving herbivore abundance and foraging activity and a decline in algal cover. The relative abundance (MaxN) and foraging activity (bite rate) of each taxa were examined pre and post-removal using video quadrats. The overall relative abundance of roving herbivores was not influenced by the removal of P. adelus. No changes in foraging patterns were observed for parrotfish, the family that received the highest rate of agonistic interactions, and rabbitfish. The removal of P. adelus resulted in a significant decrease in surgeonfish feeding, suggesting P. adelus alters foraging patterns indirectly through territorial maintenance and not aggression. The only measurable benthic impact of the P. adelus removal was an increase in sediment, while all other substratum types remained constant. These results indicate that P. adelus does not have a negative impact on all roving herbivores and instead may contribute to surgeonfish foraging indirectly through the removal of sediment. The generalisation that territorial damselfish reduce foraging rates of roving herbivores may not be applicable in all systems or for all species.

Predators may have consumptive (lethal) and non-consumptive (sub-lethal) effects on prey. Non-consumptive effects include altered behavior and reduced growth and fecundity. Native prey may not recognize non-native predators as a threat, and therefore may suffer pronounced effects. Additionally, non-native predators may elicit different behavioral responses from prey compared to native predators. Theory predicts that consumptive effects should be greater for non-native predators (due to prey naivete), and non-consumptive effects should be greater for native predators (due to predator recognition). To test these hypotheses, I monitored bicolor damselfish (Stegastes partitus) in the presence of invasive predatory Pacific lionfish (Pterois spp.), a native predator (graysby, Cephalopholis cruentata), and an egg predator (bluehead wrasse, Thalassoma bifasciatum). Body size and location of lionfish and graysby were monitored on reefs in the Bahamas. Bicolor fecundity was measured as the number and size of egg-masses that individual fish laid. Bicolor fecundity was negatively correlated with lionfish density but not graysby or bluehead density. Neither predator had a detectable effect on bicolor body size, but lionfish density was negatively correlated with the size of mature adult damselfish. I observed behavioral responses of bicolors to the two piscivores, to bluehead wrasse, and to two herbivorous fishes (Acanthurus coeruleus, Scarus spp.) as non-aggressive controls. Bicolors changed behavior (feeding and aggression) in the presence of all native fishes, but not in the presence of lionfish. Thus, differential effects exist between native and non-native predators, and invasive lionfish pose a non-consumptive threat to bicolor damselfish via reduced growth and fecundity.

Two new species of Cardicola Short, 1953 (Aporocotylidae) are described from fishes from the Great Barrier Reef (GBR), Australia. Cardicola abu sp. n. infects the Whitley’s sergeant Abudefduf whitleyi Allen & Robertson (Pomacentridae), and is described from Wistari Reef of the Capricorn-Bunker Group, on the southern GBR. Cardicola yuelao sp. n. infects the halfmoon triggerfish Sufflamen chrysopterum Bloch & Schneider (Balistidae), and is described from off Lizard Island, on the far northern GBR. Morphological analysis and molecular phylogenetic analysis show both species agree with the concept of the genus Cardicola. Balistidae and Pomacentridae are new host families for Cardicola and for aporocotylids in general.

The damselfish Chromis chromis is typically the most abundant fish species in the rocky littoral environment of the Mediterranean Sea, where it feeds in huge shoals on incoming zooplankton and rests near the seabed each night. Research has shown that large populations of C. chromis play a fundamental role by transferring carbon, nitrogen and phosphorus directly from the pelagic system to the littoral in the form of solid and liquid wastes and therefore that this species acts as a vital conduit for nutrients. In addition, C. chromis represents a major prey item for predatory fish and seabirds, it has been shown to exert significant predation pressure on coastal zooplankton populations, but it is also a major consumer of fish eggs and hence may have a strong influence on the dynamics of other fish species. In this review paper the contention is that C. chromis represents a key species in the Mediterranean Sea rocky littoral. This view is supported by quantitative evidence that has been amassed over a number of years, but is collated here for the first time. Chromis chromis is of only minor importance to commercial fisheries (it is usually discarded), but trends in population abundance of this species can be indicative of levels of fishing pressure on other commercial species. It has been demonstrated that where predator numbers are able to recover from intensive fishing (e.g.in marine protected areas; MPAs), this is often mirrored by lower densities of C. chromis. Several papers have championed C. chromis as a possible indicator species for human disturbance. As well as being directly and indirectly affected by fishing, the species is also sensitive to a number of other anthropogenic pressures, most notably poor water quality and noise pollution.

A major goal of ecology is to explain the mechanisms that drive species distributions and ecological partitioning along gradients in the natural environment. The distributions of ecologically similar animals may depend on the degree of habitat specialization and behavioural interactions within and among species. The extent of ecological partitioning in guilds of coral reef fishes has been a matter of debate, but the roles of habitat selectivity and agonistic interactions have received little attention. Here these effects were examined by investigating fine-scale species distributions, microhabitat use, and aggression in a guild of 7 territorial damselfish species in Kimbe Bay, Papua New Guinea. We documented patterns of habitat partitioning across the 3 reef zones—reef flat, reef crest, and reef slope—with distinct patterns of distribution within these zones at extremely fine scales (1-2 m). Distinct differences between neighbouring species in the substrata selected were also observed. We hypothesized that fine-scale differences in distribution and microhabitat use could be maintained by aggressive interactions. To test this, we employed a ‘bottle’ experiment, where stimulus fish were introduced into a resident’s territory, and aggression was recorded. Aggression elicited by neighbouring species was significantly higher for all species, compared with non-adjacent species. Levels of aggression differed among species, with the most aggressive species dominating the reef crest where the most distributional overlap occurred. This study revealed a fine level of spatial partitioning among reef zones and microhabitats in this guild of damselfish, which is likely to be maintained by agonistic interactions among neighbouring species. We demonstrate that when exploring coexistence in reef fish communities, the more traditional niche mechanisms operate alongside competitive dynamics, and within highly diverse systems these ecological processes are magnified.

Large quantities of coal are transported through tropical regions; however, little is known about the sub-lethal effects of coal contamination on tropical marine organisms, including fish. Here, we measured aerobic metabolism and gill morphology in a planktivorous coral reef damselfish, Acanthochromis polyacanthus to elucidate the sub-lethal effects of suspended coal particles over a range of coal concentrations and exposure durations. Differences in the standard oxygen consumption rates (MO2) between control fish and fish exposed to coal particles (38 and 73 mg L−1) were minimal and generally not dose dependent; however, the MO2 of fish exposed to 38 mg coal L−1 (21 days) and 73 mg coal L−1 (31 days) were both significantly higher than the MO2 of control fish. Chronic coal exposure (31 days) altered gill structure in the higher coal treatments (73 and 275 mg L−1), with fish exposed to 275 mg L−1 exhibiting significant reductions in gill mucous and thinning of lamellar and filament epithelium. These findings contribute to our limited understanding of the potential impacts of coal on tropical reef species; however, most of the observed effects occurred at high coal concentrations that are unlikely under most coal spill scenarios. Future studies should investigate other contamination scenarios such as the impacts of chronic exposures to lower concentrations of coal.

Human-induced nutrient pollution threatens coral reefs worldwide. Although eutrophication disrupts coral microbiomes, often leading to coral mortality, it is unknown whether eutrophication impacts the microbiomes of other coral reef organisms. Of particular interest are herbivorous fishes, whose algae consumption is critical in maintaining healthy corals. To examine the effects of eutrophication on fish gut microbiomes, we experimentally enriched territories of Stegastes nigricans, a predominantly herbivorous damselfish that farms turf algae. Using 16S RNA sequencing, we demonstrate that hindgut and foregut microbiomes have significantly higher alpha diversity in nutrient-enriched territories as compared to unenriched controls. S. nigricans gut microbiomes also exhibited significantly different compositions across treatments. In contrast, these changes were not observed in the microbiomes of the turf algae consumed by S. nigricans, indicating that the gut microbiome changes were autochthonous. Combined, our results provide a novel example of endogenous microbial shifts in wild vertebrates caused by simulated anthropogenic stress.

To date, more than 81 species of tropical coral reef fish have been reported to hybridize in nature, spanning multiple families, including the Chaetodontidae, Pomacanthidae, and Labridae. Hybridization, however, is seemingly rare among benthic nesting species that engage in pair spawning, such as the Pomacentridae. Here, we present evidence for the first molecularly confirmed record of hybridization within the genus Dascyllus; D. aruanus and D. reticulatus. Interestingly, although many hybridization events are attributed to peripheral range effects or areas of limited overlap among otherwise allopatric species, this hybrid individual was collected from the northern Great Barrier Reef, centrally located within the distribution ranges of both species. The hybrid exhibited coloration and meristic counts intermediate between D. aruanus and D. reticulatus. Diagnostic genetic markers and subsequent microsatellites analysis confirmed that this individual was a hybrid offspring of D. aruanus and D. reticulatus, with the latter providing the maternal contribution. The occurrence of the D. aruanus × D. reticulatus hybrid on the Great Barrier Reef represents an exception to the otherwise species-specific haplotypes. The nuclear diagnostic marker which was identified during this study could serve as a hybrid indicator and benefit future hybrid investigations for hybridization between these two species.

Anthropogenic noise pollution is rapidly increasing in the marine environment. Anthropogenic noise can mask biotic sounds, disrupting the successful transmission between caller and receiver, and can cause physical, physiological and behavioural changes in some species. The effect of noise pollution produced by small motorboats is of particular interest in shallow, coastal habitats where vessel numbers are steadily increasing. The present field study examined the effect of small motorboat noise on the behaviour of the juvenile common damselfish, Pomacentrus amboinensis, and their potential to perform typical behaviours when presented with increased noise over a short time period. Behavioural observations in the field (before, 1, 10 and 20 min after the start of boat noise) found there was an immediate decrease in the boldness and relative distance moved by P. amboinensis in response to the noise produced by a boat with a 30 hp 2-stroke engine travelling 30–80 m away. However, fish appeared to return to pre-boat noise exposure behaviours within 20 min. The immediate change in behaviour may alter mortality rates in the short-term, but the potential for de-sensitization to boat noise may allow long-term persistence in noisy environments if they survive the initial disruption.

In the present study we report a set of 13 novel microsatellites isolated from and characterized for the Acapulco damselfish Stegastes acapulcoensis, a species endemic to, but widely distributed within, the Eastern Tropical Pacific (ETP) region. The loci were tested in 30 individuals from the Colombian Pacific and were highly polymorphic. The mean allele number per locus was 19.5 (± 4.03 SD) and the observed heterozygosities ranged from 0.192 to 1. Some of the loci were successfully cross-amplified and were polymorphic in three Stegastes species from the ETP: S. arcifrons, S. flavilatus and S. beebei (with 11, three and seven amplified loci, respectively). The high variability and cross-amplification success of the new set of microsatellites reported here allows these markers to be a useful resource for genetic studies of S. acapulcoensis and some of their congeners to address evolutionary, ecological and conservation-related questions in the Eastern Tropical Pacific.

The damselfish Chromis limbata is native to the Macaronesian Archipelagos (Azores, Madeira and Canaries) and the western coast of Africa between Senegal and Angola. During the austral summers of 2008 and 2009 the species was recorded for the first time in the south-western Atlantic Ocean around Campeche and Xavier Islands, in Florianopolis, Santa Catarina State, Brazil. Here, the progression of C. limbata in southern Brazilian waters is described using visual counts and genetic surveys and changes in the density of the native congener Chromis multilineata were also investigated. Underwater visual censuses of both Chromis species were carried out from 2009 to 2014. Chromis limbata tissue samples were collected and the mtDNA control region was sequenced and compared with mtDNA haplotypes from the natural range to confirm species identity, compare genetic diversity and to infer connectivity between newly established Brazilian populations. The Brazilian population of C. limbata increased significantly over the past 5 years and the effect on C. multilineata is still an open question, longer time-series data will be necessary to clarify possible interactions. The molecular analyses confirmed species identity, revealed strong haplotype connectivity among Brazilian study sites and showed a low genetic diversity in Brazil when compared with the native populations, suggesting few individuals started the invasion. Four hypotheses could explain this colonizing event: C. limbata was released by aquarium fish keepers; larvae or juveniles were transported via ship ballast water; the species has rafted alongside oil rigs; they crossed the Atlantic Ocean through normal larval dispersal or naturally rafting alongside drifting objects. The rafting hypotheses are favoured, but all four possibilities are plausible and could have happened in combination.

Territorial farmer damselfishes are facilitators that selectively farm turf algae in degraded reef patches. The effect of damselfish on algae and corals has been widely studied but the ability of the damselfish to establish farms on other substrates is less understood. In the giant clam ocean nursery in Bolinao, northwestern Philippines, farmer damselfishes, particularly Stegastes nigricans, Dischistodus prosopotaenia, and D. chrysopoecilus, make use of giant clam shells as substrate for turf algae farms. To facilitate growth of the algal crop, damselfishes reduce shading and create more space for cultivation by trimming the overhanging mantles of Tridacna gigas within their colonies. This form of habitat modification occurs within weeks, with affected clams exhibiting mantle lesions and turf algae growth on their shells. These observations suggest that damselfishes can potentially extend their farmed turf algae patches in a manner that, although not typical of natural reef conditions, may be facilitated by the availability of giant clam shells as substrate. The versatility of damselfishes in establishing turf algae farms on a different substrate and their ability to condition the habitat through active modification of other reef biota emphasize the potential of the farmer damselfish to significantly influence reef community structure and biodiversity.

Coral reefs are amongst the most diverse ecosystems on Earth where complex inter-specific interactions are ubiquitous. An example of such interactions is the mutualistic relationship between damselfishes and branching corals in the Northern Red Sea, where the fish use corals as shelter and provide them with nutrients, enhance the flow between their branches, and protect them from predators. By enhancing the flow between the coral branches, the fish ventilate the coral's inner zone, mitigating hypoxic conditions that otherwise develop within that zone during the night. Here, we tested, for the first time, the effects of the damselfish Dascyllus marginatus on photosynthesis and respiration in its host coral Stylophora pistillata. Laboratory experiments using an intermittent-flow respirometer showed that the presence of fish between the coral branches under light conditions augmented the coral's photosynthetic rate. No effect on the coral's respiration was found under dark conditions. When a fish was allowed to enter the inner zone of a dead coral skeleton, its respiration was higher than when it was in a live coral. Field observations indicated that damselfish were present between coral branches 18–34% of the time during daylight hours and at all times during the night. Considering the changes induced by the fish together with the proportion of time they were found between coral branches in the field, the effect of the fish amounted to an augmentation of 3–6% of the coral's daily photosynthesis. Our findings reveal a previously unknown positive contribution of coral-dwelling fish to their host's photosynthesis.

For coral reef organisms with bipartite lifecycles, the ontogenetic shift from the pelagic larval stage to the benthic environment is often associated with high mortality that may be influenced by the local environment as well as individual traits that alter vulnerability to predation. Habitat variability such as food availability and competition for resources can influence traits such as growth and size, ultimately affecting mortality rates as well as the strength or direction of trait-mediated mortality. In this study, we examined subregional patterns of early life-history traits (ELHTs) of a model coral reef fish (bicolor damselfish: Stegastes partitus) in environmentally and oceanographically distinct regions of the Florida Keys, USA: the relatively more productive lower Keys (LK) and the more oligotrophic upper Keys (UK). Fish arrived to reef habitats with similar larval ELHTs (larval growth, pelagic larval duration, settlement size) but experienced higher mortality in the LK. Despite variability in mortality rates, patterns of selective mortality were similar between the UK and LK. For juvenile fish, growth during the first 4 days post-settlement was significantly faster in the LK compared to the UK, potentially linked to higher productivity and food availability. Results of this study indicate that environmental variability in settlement habitat at subregional spatial scales can affect post-settlement growth and survival of young fish soon after they transition to the demersal juvenile stage in coral reef environments.

Marine heatwaves, which are increasing in frequency, duration and intensity owing to climate change, are an imminent threat to marine ecosystems. On coral reefs, heatwave conditions often coincide with periods of peak recruitment of juvenile fishes and exposure to elevated temperature may affect their development. However, whether differences in the duration of high temperature exposure have effects on individual performance is unknown. We exposed juvenile spiny damselfish, Acanthochromis polyacanthus, to increasing lengths of time (3, 7, 30 and 108 days post-hatching) of elevated temperature (+2°C). After 108 days, we measured escape performance at present-day control and elevated temperatures, standard length, mass and critical thermal maximum. Using a Bayesian approach, we show that 30 days or more exposure to +2°C leads to improved escape performance, irrespective of performance temperature, possibly owing to developmental effects of high temperature on muscle development and/or anaerobic metabolism. Continued exposure to elevated temperature for 108 days caused a reduction in body size compared with the control, but not in fish exposed to high temperature for 30 days or less. By contrast, exposure to elevated temperatures for any length of time had no effect on critical thermal maximum, which, combined with previous work, suggests a short-term physiological constraint of ∼37°C in this species. Our study shows that extended exposure to increased temperature can affect the development of juvenile fishes, with potential immediate and future consequences for individual performance.

The structures, functions, and services provided by coral reef ecosystems are deteriorating worldwide. However, not all coral reefs are affected the same way, with some showing signs of resistance and/or recovery from disturbances. Understanding the drivers and feedbacks that contribute to shifts in community structure is valuable to support resilience-based management. In this study, key community variables that influence the resilience of coral reef ecosystems were examined in 64 sites of the Mesoamerican Reef (MAR) monitored in both 2006 and 2016, as part of the Healthy Reef Initiative (HRI), using the Atlantic and Gulf Rapid Reef Assessment (AGRRA) monitoring protocol. Based on benthic cover thresholds, sites were classified into three different states: coral state (CS) with >10% live coral and 10% live coral and >5% fleshy macroalgae and; depauperate coral state (DCS)