Stegastes Fuscus Research Articles

Sound stimulus effects on dusky damselfish behavior and cognition.

Anthropogenic noises are widespread and affect marine wildlife. Despite the growing knowledge on noise pollution in the marine environment, its effects on fish cognition are scarce. Here, we investigated the effects of sound exposure on anxiety-like behavior and memory retention on dusky damselfish Stegastes fuscus. The animals were trained in a conditioned place aversion task, and exposed to two daily sessions of music at intensities of 60-70 dBA or 90-100 dBA, while the control group was kept at 42-46 dBA (no music) for five days. After that, fish were tested in the novel tank paradigm and tested for the memory of the aversive task. In the novel tank, animals exposed to sound spent more time still and decreased the distance from the bottom of the tank. Animals also spent more time on the aversive side of the conditioning tank. These results suggest that anthropogenic noise applied through high-intensity music can increase anxiety and decrease memory retention in S. fuscus, suggesting the deleterious potential of noise for reef species.

Agonistic Behavior Is Affected by Memory in the Dusky Damselfish Stegastes fuscus.

The ability to discriminate familiar from unfamiliar conspecifics has been demonstrated in several species of fish. Agonistic interactions are among the most frequent behaviors exhibited by territorial species and could offer useful information for the individual recognition process. In agonistic situations, memory may modulate the behavioral response and affect social dynamics, but few studies have explored the memory retention acquired during aggressive encounters. The present study investigated the memory retention of an agonistic encounter in the dusky damselfish Stegastes fuscus. The experimental procedure was divided into three parts: (1) Familiarization; (2) Recognition test; and (3) Memory test. During the familiarization phase, the fish were visually exposed to the same conspecific for 5 days (10 min per day) and the behavior was recorded. On the following day (conspecific recognition test), half of the animals were paired with the same conspecific and the other half with a different conspecific for 10 min, and the behavior was recorded. The fish were retested 5, 10, and 15 days after the test to evaluate memory retention. In the memory test, they were exposed to the same conspecific as before or to a different conspecific. We found that the damselfish reduced their agonistic displays when the stimulus fish was familiar, but when it was unfamiliar, the animals were more aggressive and only reduced their mnemonic response after 10 days. These results suggest that the recognition ability of damselfish can be affected by time and that it modulates agonistic response.

Drivers of damselfishes distribution patterns in the southwestern Atlantic: tropical and subtropical reefs compared

Abstract Damselfishes are known keystone species of reef environments, however large-scale distribution patterns are poorly studied in the southwestern Atlantic. We evaluated main drivers of distribution of three conspicuous damselfishes, along tropical and subtropical coastal systems, in Brazil. Abundances were assessed against wave exposure, depth (within 1–7 m in tropical and 1–11 m in subtropical reefs) and benthic cover. Despite differences between systems, exposure and depth consistently explained damselfishes distribution. Stegastes fuscus, the larger damselfish species of the genus in the southwestern Atlantic, was dominant in both systems, inhabiting preferably shallow and sheltered reefs. Conversely, Stegastes variabilis occupied shallow habitats with higher exposure. Stegastes pictus was absent from tropical reefs sampled, inhabiting depths >7 m, in subtropical reefs. Species were weakly associated with benthic features, which poorly predicted changes in abundances. Regardless, S. fuscus showed association with articulated calcareous algae, and S. variabilis juveniles associated with erect macroalgae. Despite occurring in very distinctive reef systems, Brazilian damsels habitat requirements are consistent in both tropical and subtropical reefs. While highly persistent species, long term monitoring will inform us how they respond to pervasive global changes and human impacts along Brazilian reefs.

Land-based noise pollution impairs reef fish behavior: A case study with a Brazilian carnival

Anthropogenic sounds have spread across the biosphere, with threats from individual welfare to ecosystem health. Sounds are important to animals in both terrestrial and aquatic environments and detrimental effects have been shown across a wide range of taxa. Despite the ever-growing transformation of coastal lands by human activities, pollutant effects of sounds that propagate from land into coastal water (across realms) have been largely overlooked. We here show that the Brazilian carnival of Salvador, annually taking place along a coastal boulevard, elevated underwater sound pressure levels by more than 30 dB re 1 μPa2. We used remotely operated cameras to measure individual abundance and feeding activity of the Brazilian damsels (Stegastes fuscus) and we measured its flight-initiation distance to a model predator. Brazilian damsels did not abandon their reef territories, but their feeding activity and fleeing distance were significantly reduced under elevated noise levels, compared to the ambient control conditions at the same site and at a spatial control site. Apparently, carnival sounds emitted from land affected underwater behavior in our reef fish species. The behavioral effects may be critically important for individual fitness, and the detrimental impact of land-based noise pollution in coastal waters may also apply to other fish and invertebrate species. Humanity is claiming coastlines at a faster rate than any other habitat, and conservation concerns should extend to nearby coastal ecosystems and the possible impacts of underwater sounds emanating from land.

Fighting off the intruder: context-dependent territory defence in the damselfish Stegastes fuscus

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.

Damselfish face climate change: Impact of temperature and habitat structure on agonistic behavior.

Oceans absorb a huge part of the atmospheric heat, leading to the rise in water temperature. Reefs are among the most affected ecosystems, where the complex behavioral repertoire of fishes is usually an indicator of environmental impacts. Here, we examined whether temperature (28 and 34°C) and habitat complexity (high and low) interact to affect the agonistic behavior (mirror test) of the dusky damselfish (Stegastes fuscus), a key species in Brazilian reefs because of its gardening capacity and territorial behavior. Higher temperatures altered basal behavior in both high and low-complexity conditions. Fish kept at 28°C under the high-complexity condition were more aggressive than those at a higher temperature (34°C) and in a low-complexity condition, which also exhibited lower dispersion. Our data show that changes in behavior of coral reef fish is associated to fluctuations in environmental conditions. Thus, it is important to implement management or conservation strategies that could mitigate global change effects.

Structural complexity but not territory sizes influences flight initiation distance in a damselfish

The fear of predators can lead to behavioral changes in their prey, but animals must trade off defensive behavior against other compelling needs. For territorial species, responding to predators may be especially costly, because defense and escape are mutually incompatible. A growing literature documents risk assessment in fish, but a few studies have focused on extremely territorial fish, and nothing is known about how territory size, territorial interactions, habitat structural complexity, and life stage may modify risk assessment. We studied this in a damselfish (Stegastes fuscus) on coral reefs and measured risk assessment using flight initiation distance (FID). We found that only structural complexity explained variation in FID; fish in more complex habitats tolerated closer approach. Our study suggests that individuals in relatively more structurally complex territories are bolder than those that occur in less complex territories. Documenting the relative importance of these variables is important, because antipredator behavior influences not only the predator–prey relationship, but can also generate cascading effects, and influence the structure of the community and potentially entire ecosystems.

Fear-induced behavioural modifications in damselfishes can be diver-triggered

Fear is a short-term response arisen from the way an animal perceives its environment when some threat makes it insecure. Thus, the risk perception of predation shapes the cost-benefit decisions associated with food and safety in animal communities. Even non-consumptive human-related activities such as ecotourism may influence species behavioural traits. Marine wildlife tourism might produce different impacts on organisms, stressing and modifying (directly or indirectly) species behaviour, physiology and habitat use. Understand the effects of human presence on site-attached fish’ behaviour is crucial to elucidate how dive-tourism could shape their limited-range seascape. Given the importance of the territorial damselfishes as reef farmers and ‘ecosystems engineers', here we investigated if the presence of SCUBA divers and snorkelers can disrupt the foraging and territorial defence of the Dusky damselfish, Stegastes fuscus. Experimental approaches (diver presence and absence) were applied in 30 territories of S. fuscus using underwater remote video cameras. Behavioural responses were analysed by considering the frequency of refuge, foraging and chase behaviours. Both recreational dive activities had an analogous role in frighten and disturb the Dusky damselfish activities. Considering the frequency of behaviours displayed in diver's absence vs presence, S. fuscus increased its refuge times from approximately 2% to 50% on SCUBA diver presence and from 9% to 43% in snorkeler presence. It is directly linked to the missed feeding opportunities, which reduced by half during both diver's presence. Damselfish's aggressiveness proportionally dropped (0.3%) during SCUBA diver presence but increased (2.4%) while snorkeler was present. However, the average frequency of chase behaviour reduced with both divers' approach. Interruptions in damselfish behaviour may modify the resource monopolization and productivity inside their territories, affecting its relationships with other species beyond the boundaries of their territoriality, and leading a possible change on its functional role in the reef community. Territorial reef fish behaviour and their relationship with divers' presence can provide a more holistic comprehension regarding the seascape of fear concept and could be useful as an indicator of human disturbances.

Trophic relationships in tidepool fish assemblages of the tropical Southwestern Atlantic

AbstractTrophic studies are fundamental to understanding the dynamics of assemblages and functional roles of species within ecosystems, contributing to the identification of factors responsible for the organization and structure of communities. This study aimed to analyse the trophic organization of tidepool fish assemblages in the tropical Southwestern Atlantic, based on the underlying idea that food resources are not limiting and that trophic guild formation is not driven by food competition. Diets were based on feeding index values of food categories for 12 representative species collected in six tidepools (20º49′ S, 40º36′ W) at quarterly intervals (2005 to 2007). The main food categories were small crustaceans, polychaetes and macroalgae. Multivariate techniques evidenced two multispecific trophic guilds: small‐prey carnivores, including Bathygobius soporator, Bathygobius geminatus, Malacoctenus delalandii and Halichoeres poeyi, and herbivores, including Sparisoma axillare and Acanthurus bahianus. Other species presented significantly different diets and were classified into the following guilds: omnivores feeding on filamentous algae and copepods (Abudefduf saxatilis); large‐prey carnivores (Labrisomus nuchipinnis); omnivores feeding on polychaetes and filamentous algae (Stegastes fuscus); and polychaete feeders (Ahlia egmontis). Gymnothorax funebris and Gymnothorax moringa were classified as carcinophagores and piscivores, respectively. Trophic organization appears related to species convergence toward the use of abundant food resources, driven by a combination of factors allowing some resource partitioning through inter‐specific differences in consumer size, microhabitat, behavior, and trophic specialization.

Local variations in microhabitat use by Stegastes fuscus (Cuvier, 1830) (Teleostei: Pomacentridae) in a tropical reef of Brazil

Due to their widespread abundance and territorial habits, damselfishes play central roles in reefs worldwide, but the extent to which they modify the reef's substrate varies both amongst and within species. The present study evaluated microhabitat preferences and the role of the common damselfish Stegastes fuscus (Cuvier, 1830) (Teleostei: Pomacentridae) as a benthic community modifier in a tropical algal-dominated reef. We employed video survey techniques to assess fish density and microhabitat use and, additionally, the biomass of sessile components were compared inside and immediately outside algal farms of S. fuscus. Individuals showed pronounced microhabitat preference, but with prominent local (i.e. small-scale) variations in benthic cover. These local variations are reported for the first time and were due to individuals defending one of two contrasting microhabitats (i.e. turf-dominated or Palythoa caribaeorum-dominated). Further, significant differences in the biomass of sessile organisms were observed within algal farms suggesting that S. fuscus plays a keystone role in the benthic community of the reef. The implications of the prominent local variation in microhabitat use are discussed and strongly illustrate the behavioral plasticity of this damselfish.

Otolith fingerprints of the coral reef fish Stegastes fuscus in southeast Brazil: a useful tool for population and connectivity studies

Otolith fingerprinting is a useful tool in determining the population structure, movement patterns and connectivity among fish habitats. Damselfish, Stegastes fuscus, is a highly abundant reef fish species in the Brazilian coasts. It has been assessed as least concern species according with the IUCN Red List. One hundred and twenty adults, ranging from 85 to 120 mm standard length, were collected in April 2013 by spear fishing in six coastal islands located on Cananéia, Paranaguá, Guaratuba and Babitonga bays, southeast Brazil. Elemental and isotopic signatures of whole sagittae were determined by inductively coupled plasma mass spectrometry and isotope ratio mass spectrometry, respectively. Element:calcium (Sr:Ca, Ba:Ca, Mn:Ca and Mg:Ca) and isotopic ratios (δ18O and δ13C) were analyzed with univariate and multivariate statistics to determine whether these fingerprints can be used to assess the degree of separation between the individuals of these geographic locations. Whole otolith fingerprints representative of the fish entire life-history gave distinct small scale spatial signatures confirming that S. fuscus is a sedentary reef species. Classification accuracy rate obtained from quadratic discriminant function analysis of whole otolith chemistry data was relatively high (71% of mean accuracy percentage). Furthermore canonical analysis of principal coordinates from otolith signatures showed the existence of three regional groups probably a consequence of the similarity of the major estuarine systems that characterize the environment of the nearby coastal islands where fish were collected. This study suggests that otoliths can be used to study the population structure and assess connectivity of the damselfish, providing new knowledge to adequately manage this species.

The influence of fire-coral colony size and agonistic behaviour of territorial damselfish on associated coral reef fish communities

Branching hydrocorals from the genus Millepora play an important ecological role in South Atlantic reefs, where branching scleractinian corals are absent. Previous studies have shown a high proportion of reef fish species using branching fire-coral colonies as shelter, breeding, and feeding sites. However, the effects of Millepora spp. colony size and how the agonistic behaviour of a competitive damselfish affect the associated reef fish community are still unknown. The present study examined how fire-coral colony volume and the presence of a highly territorial and aggressive damselfish (Brazilian endemic Stegastes fuscus) affects the reef fish community associated with the fire-coral Millepora alcicornis. M. alcicornis colonies were surveyed from September 2012 to April 2013 at Tamandaré Reefs off Northeast Brazil. Our results show that the abundance and richness of coral associated fish was positively correlated with M. alcicornis coral colony volume. Additionally, behaviour of S. fuscus, the most abundant reef fish species found associated with fire-coral colonies (almost 57% of the fish community), was also influenced by fire-coral colony volume. There was a clear trend of increased agonistic behaviour and feeding on coral polyps as colony volume increased. This trend was reversed for the non-occupational swimming category, which decreased as M. alcicornis colony volume increased. Behavioural ontogenetic changes were also detected for S. fuscus individuals. Juveniles mainly showed two distinct behaviours: sheltered on coral branches and feeding on coral polyps. In contrast, adults presented greater equitability among the behavioural categories, mostly non-occupational swimming around coral colonies and agonistic behaviour. Lastly, S. fuscus individuals actively defended fire-coral colonies from intruders. A large number of agonistic interactions occurred against potential food competitors, which were mainly roving herbivores, omnivores, and sessile invertebrate feeders. To our knowledge, the present study provides the first evidence that through habitat competition, the presence of S. fuscus may affect reef fish communities associated with M. alcicornis coral colonies. Our findings also indicate that S. fuscus uses M. alcicornis coral colonies as part of their territory for shelter and foraging. In conclusion, M. alcicornis fire-coral colonies are extremely important habitats for reef fishes and the size and presence of a territorial damselfish are relevant variables for associated reef fish community.

Dusky damselfish Stegastes fuscus relational learning: evidences from associative and spatial tasks.

This study investigated the ability of the dusky damselfish Stegastes fuscus to associate conditioned and unconditioned stimuli (single CS-US) and to find a specific place in a clueless ambiece (spatial learning). After tested for colour preference and showing no specific colour attractively, the fish were trained to associate a colour cue with a stimulus fish (conspecific). Fish were then challenged to locate the exact place where the stimulus fish was presented. Stegastes fuscus spent most time close to the zone where stimulus was presented, even without obvious marks for orientation. The results confirm that S. fuscus show single CS-US learning and suggest the fish ability for spatial orientation. Stegastes fuscus appears to use multiple senses (sight and lateral line) for cues association and recall, and appear to perform relational learning similar to mammals. These data suggest the importance of cognitive skill for reef fishes that may have contributed to their establishment and evolutionary success in such complex environment.

Distribution and feeding patterns of juvenile parrotfish on algal‐dominated coral reefs

AbstractBy the consumption of algae, parrotfishes open space for young coral settlement and growth, thus playing a central role on the maintenance of coral reefs. However, juvenile parrotfish ecology is often overlooked due to the difficulty discerning species during this phase. Herein, we present the first attempt to investigate changes in habitat use and diet that happen to juveniles of the Redeye parrotfish Sparisoma axillare, focusing on four zones within an algal‐dominated reef: the macroalgal beds, back reef, reef flat, and fore reef. Smaller S. axillare juveniles (<5 cm) preferred to inhabit the macroalgal beds and the reef flat, whereas juveniles larger than 5 cm were more abundant in the back and fore reefs due to distinct post‐settlement habitat conditions. Aggressive interactions with the territorial damselfish Stegastes fuscus were the primary driving factor of juvenile distribution and feeding rates. Attack rates increased with juvenile size and the lowest bite rates were observed in zones with higher densities of territorial damselfish. In previous studies, the persistence of parrotfish recruits in habitats dominated by damselfish was reduced, but newly settled parrotfish occurred more densely within the damselfish domain by behaving as a cryptic reef fish. As these juveniles grew, their bite rates increased, a change associated with a shift from cryptic to roving behavior. Feeding preferences were determined by substrate cover, where juveniles fed on available food sources in each habitat. Juveniles relied on jointed calcareous algae in habitats dominated by these algae, a pattern not observed for thick leathery algae. Filamentous algae were the preferred food for smaller fish; for individuals greater than 10 cm, a higher ingestion of sand was observed. Most studies evaluating the functional role of parrotfish do not consider species feeding preferences. However, the potential for a species to turn an impacted reef back to a coral‐dominated phase is influenced by their food selection, which is dependent on the algal species composition.

Estrutura Populacional e Período Reprodutivo do Peixe Donzela Stegastes fuscus (Cuvier, 1830) das Poças de Maré da Praia de Búzios, Rio Grande no Norte, Brasil

O peixe-donzela, Stegastes fuscus (Osteichthyes, Pomacentridae) ocorre frequentemente nas poças de maré do Rio Grande do Norte. O objetivo deste estudo foi caracterizar a estrutura populacional em comprimento e peso e período reprodutivo de S. fuscus nos arrecifes rochosos costeiros de Búzios, RN, Brasil.

Checklist of rocky reef fishes from the Currais Archipelago and Itacolomis Island, Paraná state, Brazil

The ichthyofauna of the rocky substrate of Currais Archipelago and Itacolomis Island (Paraná state, Brazil) was surveyed between October 2008 and August 2009 through visual census, using 40 m2 (20x2 m) band transects at an average depth of 6 m. A total of 14,210 individuals (66 species from 33 families) were observed in 336 band transects, covering an area of 13,440 m2. Stegastes fuscus, Abudefduf saxatilis, Haemulon aurolineatum and Malacoctenus delalandii were the most abundant species. “Carnivore” was the most species-rich category, and “Mobile Invertebrate Feeder” the most abundant. Nine species are added to the list of reef fishes of the Paraná state: Acanthurus coeruleus, Dactylopterus volitans, Epinephelus morio, Myrichthys breviceps, Ophioblennius trinitatis, Paraclinus spectator, Scorpaena brasiliensis, and Selene vomer.

Territorial hypothesis predicts the trade off between reproductive opportunities and parental care in three species of damselfishes (Pomacentridae: Actinopterygii)

Paternal care is rare in most animals, but common in fishes, including Pomacentridae. One way of explaining it is through the territorial hypothesis, which predicts that paternal care may evolve when caring for a territory with eggs will not cost more than territories without eggs. Here we describe the reproductive behavior of three pomacentrids from Sao Paulo, Brazil, and evaluate if the territorial hypothesis explains their behavioral variation through five predictions. We checked if females have multiple spawns (prediction 1), if they forage more (prediction 2) and if territory defence demands more when eggs are present (prediction 3). We also described how visible eggs are (prediction 4) and how available nesting sites are (prediction 5). Chromis multilineata differed from Abudefduf saxatilis and Stegastes fuscus by not guarding the eggs, spending less time with territoriality and fanning eggs; and more time feeding and foraging. Females of the three species are iteroparous. Females' A. saxatilis and S. fuscus foraged more than males, which spent the same amount of time in territorial defence before and after eggs were delivered. These two species also have very conspicuous egg clutches on clean rock surfaces defended by them. On the other hand, males and females of C. multilineata spent the same time foraging, while territoriality took more effort after eggs were present and it spawns cryptic eggs amid Sargassum, a common and disperse micro-environment in Sao Paulo rocky shores. Territorial hypothesis explains why paternal care by A. saxatilis and S. fuscus lasts longer than by C. multilineata.

Thermal impact of a nuclear power plant in a coastal area in Southeastern Brazil: effects of heating and physical structure on benthic cover and fish communities

The influence of a nuclear power plant’s cooling water and physical structure on benthic cover and fish communities were assessed in a coastal area in Southeastern Brazil. We hypothesised that thermal discharges decrease benthic cover and consequently, change the associated rocky reef fish assemblage structure and that physical structure is directly associated with fish richness and diversity. Twelve sites at different distances (close, near and far) from thermal discharge and types of physical structure (low and high) were sampled by visual census. The average surface temperature at the most impacted sites (close) ranged from 30.5 to 31°C, while at far sites it ranged from 25.5 to 28.5°C. Although thermal influences have decreased benthic cover, and consequently, decreased fish richness and diversity, we found that in near and far sites that had complex habitat structures (physical and benthic cover) fish communities were unaffected. The greatest abundances of Eucinostomus argenteus, Mugil curema and Sphoeroides greeleyi were associated with the highest temperatures at the most impacted sites. In contrast, Abudefduf saxatilis, Chaetodon striatus, Stegastes fuscus, Diplodus argenteus and Malacoctenus delalandii were more abundant at high structured sites far from thermal discharges. Our data support the hypothesis that thermal discharge decreases benthic cover, fish richness and diversity but physical structure, when coupled with high diversity and abundant benthic cover, minimised thermal effects on fish communities.

The fitness of the Brazilian damsel Stegastes fuscus is increased by sharing the territory with the dusky grouper Epinephelus marginatus

Stegastes fuscus and Epinephelus marginatus are known for co-habiting shelters. The damselfish S. fuscus uses the territory for nesting and must protect its eggs from grazers; the grouper E. marginatus is an omnivorous sit-and-wait predator. This study aims to evaluate the effect of juvenile groupers on the reproductive success of the Brazilian damsel. Twenty-five hours of underwater observations were done in Sao Sebastiao and Ilhabela, Northern shore of Sao Paulo, Brazil. Fitness increase was measured by the egg-clutch area and number of contributing females in 130 nests shared by groupers and another 130 where damselfishes stood alone. An egg predator crab was placed into the damselfish territory, and behavioural responses during 2 min were recorded for nests with or without E. marginatus, 80 replicates each. Nests shared by the dusky groupers had more eggs and received eggs from more females too. While fathers who were alone in the territory had to deal with the egg predator crab, in shared nests, the grouper would take care of the intruder, sometimes feeding on it. Therefore, the Brazilian damsel may benefit from the presence of the dusky grouper by increasing the fitness and diminishing the costs of parental care.

Effects of a nuclear power plant thermal discharge on habitat complexity and fish community structure in Ilha Grande Bay, Brazil

Fish communities and habitat structures were evaluated by underwater visual censuses a rocky location impacted by thermal discharge (I) and at two control locations, one in a Sargassum bed (C1) and the other in a rocky shore with higher structural complexity (C2). Habitat indicators and fish communities exhibited significant differences between the impacted and control locations, with the impacted one showing a significant decrease in fish species richness and diversity, as well as a decrease in benthic cover. At the I location, only 13 fish species were described, and the average water temperature was 32 ± 0.4 °C, compared with 44 species at C1 (25.9 ± 0.3 °C) and 33 species at C2 (24.6 ± 0.2 °C). Significant differences in fish communities among locations were found by ANOSIM with Eucinostomus argenteus, Mugil sp. and Haemulon steindachneri typical of location I, while Abudefduf saxatilis, Stegastes fuscus and Malacoctenus delalandi were typical of the control locations. Our study shows that thermal pollution alters benthic cover and influences fish assemblages by altering composition and decreasing richness.