Behaviour Of Reef Fishes Research Articles

Farming behaviour of reef fishes increases the prevalence of coral disease associated microbes and black band disease.

Microbial community structure on coral reefs is strongly influenced by coral-algae interactions; however, the extent to which this influence is mediated by fishes is unknown. By excluding fleshy macroalgae, cultivating palatable filamentous algae and engaging in frequent aggression to protect resources, territorial damselfish (f. Pomacentridae), such as Stegastes, mediate macro-benthic dynamics on coral reefs and may significantly influence microbial communities. To elucidate how Stegastes apicalis and Stegastes nigricans may alter benthic microbial assemblages and coral health, we determined the benthic community composition (epilithic algal matrix and prokaryotes) and coral disease prevalence inside and outside of damselfish territories in the Great Barrier Reef, Australia. 16S rDNA sequencing revealed distinct bacterial communities associated with turf algae and a two to three times greater relative abundance of phylotypes with high sequence similarity to potential coral pathogens inside Stegastes's territories. These potentially pathogenic phylotypes (totalling 30.04% of the community) were found to have high sequence similarity to those amplified from black band disease (BBD) and disease affected corals worldwide. Disease surveys further revealed a significantly higher occurrence of BBD inside S. nigricans's territories. These findings demonstrate the first link between fish behaviour, reservoirs of potential coral disease pathogens and the prevalence of coral disease.

Behavioural impairment in reef fishes caused by ocean acidification at CO2 seeps

Laboratory experiments have shown that the behaviour of reef fishes can be impaired by the CO2 levels projected to occur in the ocean by the end of this century. Research now shows that reef fishes at natural volcanic CO2 seeps also exhibit behavioural abnormalities, and that behaviour does not acclimate with extended exposure to high CO2. Fish communities are therefore likely to face a serious threat from CO2-induced behavioural abnormalities in the future as ocean acidification becomes widespread.

Coral reef fish association and behaviour on the fire coralMilleporaspp. in north-east Brazil

The branching structure of the coral colonies from the genusMilleporaprovides substrate, shelter, and food resources for several reef organisms, such as fish and invertebrates. The present work analysed the association and behaviour of reef fish on the fire coralMillepora alcicornisandM. brasiliensisfrom September 2010 to February 2011, on the coastal reefs of Tamandaré, north-east Brazil. A total of 473 reef fish individuals of 27 species were sighted associated with the coral colonies, mainly composed of juveniles (65%). The most frequently observed behaviours were sheltered/stationary and swimming close to the coral; however, individuals were also observed foraging and breeding amongMilleporaspp. branching colonies. The agonistic behaviour performed byStegastes fuscusindividuals was highlighted in the present study, especially againstChaetodon striatus, Diodon holacanthusandOphioblennius trinitatisindividuals.Milleporaspp. hydrocorals are ecologically important for juvenile and adult reef fish belonging to several trophic guilds. The complex structure of the coral colonies provides a wide variety of ecological functions on coral reefs (e.g. shelter, reproduction area, food and even territory). Nevertheless, the abundance of branching fire coral in Brazilian reefs have been declining over the past years; therefore, efforts must be made to protect this key habitat.

Physical habitat and social conditions across a coral reef shape spatial patterns of intraspecific behavioral variation in a demersal fish

AbstractAs coral reef ecosystems decline in health worldwide, reef‐associated fishes are being impacted by changes to their coral reef habitats. While previous studies have shown coral reef structure to affect the demography of reef fishes, changes in reef conditions may also impact the behavior of reef fishes as they cope with altered habitats. In this study, we examined spatial patterns of intraspecific behavioral variation in the bicolor damselfish (Stegastes partitus) across the fringing reefs of Curaçao (Caribbean Sea), and explored how this behavioral variation associated with physical and social conditions on the reef. Principal components analysis (PCA) condensed physical parameters of the reef into principal component 1 (PC1), comprising depth, coral cover (%), rugosity, and average hole size (cm2), and principal component 2 (PC2), which represented the number of holes. PC1, but not PC2, increased spatially across the reef as the habitat transitioned from coral rubble in the shallows to live coral on the reef slope. This transition in reef structure was paralleled by changes in social conditions including decreases in bicolor damselfish density in habitats with higher PC1 values. The behavior of bicolor damselfish also varied spatially with greater aggression and more frequent shelter use in habitats with lower PC1 values. Path analysis revealed robust associations between this behavioral variation and physical habitat conditions of the reef, indicating that physical – rather than social – habitat variation is the primary determinant of these spatial patterns of intraspecific behavioral variation. Taken as a whole, this coupling between physical reef structure and behavior suggests that reef fish may show altered behaviors on coral reefs degraded by anthropogenic impacts.

Does environmental noise really affect reef fish behavior or are they talking while we cannot listen to them?

Although it has been hypothesized that reef fish reduces sound production during extreme environmental events, it is possible that fish sounds are still present but only masked by elevated environmental noise. Although available acoustic technology makes it difficult to address this question, we can still generate hypotheses about the impact of environmental noise on fish sound production. Is there a behavioral response to environmental noise, or are fish sounds present at the same levels but masked and therefore undetectable without adequate filters? We recorded sciaenid (Pisces: Sciaenidae) sound production around Isla Tortuga, Costa Rica, during the “Nortes,” a period of strong winds caused by cold fronts and extreme variation of atmospheric pressure. Sciaenid sounds apparently stopped with almost no emissions during strong winds (56 miles/h) and transitioned to the normal emission rate on the next day when winds receded to 2 miles/h. We hypothesize that fish sounds were present at all times, but masked by wind-produced noise instead of a biological modulation as described by Mann and Grothues (2009) in similar conditions. I present circumstantial evidence in support of this hypothesis and discuss possible methods to test it directly.

Settlement-stage coral reef fish prefer the higher-frequency invertebrate-generated audible component of reef noise

The importance of the acoustic cuescape is often overlooked in studies of animal orientation. Recent studies have shown that reef noise affects the behaviour and orientation of settlement-stage coral reef fish. This response may simply facilitate orientation to reefs; alternatively, acoustic habitat cues could also facilitate the remote selection of suitable settlement habitats. To test which components of reef noise evoke behavioural responses in larval fish, we used light traps to measure the responses of a diverse range of settlement-stage fish to the filtered ‘high’ (570–2000 Hz)- and ‘low’ ( 10 individuals, four (Pomacentridae, Apogonidae, Lethrinidae and Gobiidae) were caught in significantly greater numbers in the high-frequency traps than either the low-frequency or the silent traps. The Syngnathidae preferred high- to low-frequency traps, while the Blenniidae preferred high-frequency to silent traps. Only the Siganidae showed no preference between any of the sound treatments. Although some species-level variation in response was found, the general trend was a preference for high-frequency traps. This study suggests that most settlement-stage fish select the higher-frequency audible component of reef noise, which is produced mainly by marine invertebrates, as a means of selectively orienting towards suitable settlement habitats. The results highlight potential impacts of anthropogenic noise pollution and habitat modification in affecting the natural behaviour of reef fish at a critical stage in their life history.

Complex habitats may not always benefit prey: linking visual field with reef fish behavior and distribution

Habitat structural complexity is often considered beneficial for prey species because it reduces the foraging efficiency of predators. However, for site-attached, territorial prey, such as many damselfishes, structural complexity at specific scales may be detrimental. Since the location of territorial prey could be highly predictable to predators, the ability of such prey to detect approach- ing predators may be limited by high-relief structural complexity. The bicolor damselfish Stegastes partitus is abundant and randomly dispersed on coral heads in fore reef habitats in the Florida Keys but is less abundant on back reef habitats, where it aggregates in open patches within fields of gor- gonian soft corals. We hypothesized that the complex gorgonian habitat limits the visual field for S. partitus, increasing the uncertainty about predation risk, and is therefore a low quality habitat. We found that males occupy territories with visual fields larger than the fields around randomly selected points. Experimentally reducing the visual field around males decreased both their courting rates and the distance they ventured away from the nest. Males in the back reef spent more time away from their nests—potentially taking greater risks—towards the peak of the spawning cycle than males in the fore reef, which may be related to their lower reproductive success on the back reef. Experiments exposing male S. partitus to a fish predator suggest that a limited visual field (an uncertain situation) presents a more risky situation than a clearly visible but 'contained' predator. Our results demon- strate that a limited visual field around territorial, site-attached prey fish alters their behavior such that mating and feeding may be compromised. Fish abundance was negatively correlated with soft coral density but not with the number of potential territories or surface rugosity, suggesting that the visual seascape may be important for the fish distribution patterns. We suggest that habitat complex- ity at the appropriate scale mediates the distribution and possibly also the abundance of territorial prey fishes through the effects of the size of the visual field on fish behavior.

Diversity of fish courtship and spawning sounds and application for monitoring reproduction

It has been known for a long time that many fishes produce sounds especially during reproduction. Recent studies using a novel system for synchronous audio and video recordings underwater reveal that several species produce species specific and behavior specific sounds exclusively associated with courtship and the mating act. Passive acoustic technology can utilize these sounds to remotely monitor the breeding behavior of reef fishes. This application is being tested as an alternative or supplement to the traditional methods involving sampling fish gonads, ichthyoplankton net collection, and direct observation by scuba diving. This presentation will show a video with sounds of fishes courting and spawning and will describe their acoustic characteristics.

Spatial Patterns of Aggression, Territory Size, and Harem Size in Five Sympatric Caribbean Parrotfish Species

Territorial behaviour is a conspicuous determinant of social organisation in many reef fishes including parrotfishes. Most parrotfish studies in the Caribbean have focused on the species Scarus iserti and Sparisoma viride over limited ranges of reef habitat. By contrast, our study has included all common parrotfishes in Belize (Sc. iserti, Sp. viride, Sparisoma aurofrenatum, Sparisoma chrysopterum, and Sparisoma rubripinne) at three sites with different physical and biotic conditions and a wide range of fish densities. Density in Sc. iserti was strongly positively correlated to substrate rugosity. In contrast, densities of Sp. chrysopterum and Sp. rubripinne were unrelated to rugosity and territories were large. Territory size was smallest in Sc. iserti (mean areas at the three sites ranged from 41 to 120 m2) and largest in Sp. rubripinne (ranged from 168 to 1400 m2). All species except Sp. chrysopterum exhibited significantly larger territories where density was low as suggested by territory theory. Territory size decreased rapidly with increasing density of competitors. Patterns of harem size differed between two groups of parrotfishes. (1) Sc. iserti, Sp. viride, and Sp. aurofrenatum exhibited an expected positive correlation with territory size. (2) Harem size was smaller in Sp. rubripinne and Sp. chrysopterum, and showed no spatial pattern. Aggression in Sp. viride and Sc. iserti was directed entirely towards intraspecifics and positively density dependent. Interspecific interactions accounted for only 10% of observations and were recorded exclusively whilst following Sp. chrysopterum, Sp. rubripinne, and, to a lesser extent, Sp. aurofrenatum. A meta analysis of species interactions suggested that intraspecific interactions were most common where overall fish density was greatest and conversely, interspecific interactions occurred more often at lower densities. This may suggest that the economic defensibility of territories is largely confined to intraspecifics where density is greatest. Most (62%) of the interspecific interactions comprised Sp. rubripinne chasing the smaller species Sp. chrysopterum, suggesting that territorial behaviour has at least some non-reproductive origin and may therefore be associated with either food or shelter. It is feasible that at such low population densities, it is economically feasible for Sp. rubripinne to defend against intraspecifics and Sp. chrysopterum. Social behaviour in Sp. chrysopterum and Sp. rubripinne, and to a lesser extent Sp. aurofrenatum, differs to that of Sc. iserti and Sp. viride which conform to existing theories of social behaviour in reef fish.

Hot topics in animal bioacoustics

Recent discoveries in the field of animal bioacoustics include everything from active auditory mechanics in insects to the behavior of large marine mammals in response to manmade sounds. Using laser Doppler vibrometry, Göpfert and Robert found that active auditory mechanics in male mosquitoes provides tuning that allows them to detect flying females. Their exciting discovery revealed new similarities between insect and vertebrate hearing. Many researchers have reported the behavior of fishes and marine mammals in response to underwater manmade sounds that is most likely controlled by other factors than the sound itself. Wardle and his colleagues found that repeated firing of seismic air guns had little effect on the day-to-day behavior of reef fishes off the coast of Scotland unless the explosions were visible. Madsen and Mo/hl also reported no change in behavior or click rate of sperm whales when detonators were discharged off the coast of Norway. Thus marine animals may not swim away from anthropogenic sounds even though they could be harmful. Gerstein determined masked thresholds and critical ratios for manatees that may prevent them from detecting boat noise in their natural habitat. His findings will lead to new solutions enabling manatees to detect boats and avoid collisions.

Parasite infection rather than tactile stimulation is the proximate cause of cleaning behaviour in reef fish.

Cleaning behaviour is a popular example of non-kin cooperation. However, quantitative support for this is generally sparse and the alternative, that cleaners are parasitic, has also been proposed. Although the behaviour involves some of the most complex and highly developed interspecific communication signals known, the proximate causal factors for why clients seek cleaners are controversial. However, this information is essential to understanding the evolution of cleaning. I tested whether clients seek cleaners in response to parasite infection or whether clients seek cleaners for tactile stimulation regardless of parasite load. Parasite loads on client fish were manipulated and clients exposed to cleaner fish and control fish behind glass. I found that parasitized client fish spent more time than unparasitized fish next to a cleaner fish. In addition, parasitized clients spent more time next to cleaners than next to control fish, whereas unparasitized fish were not attracted to cleaners. This study shows, I believe for the first time, which is somewhat surprising, that parasite infection alone causes clients to seek cleaning by cleaners and provides insight into how this behaviour evolved.

Behaviour of pelagic larvae of four coral-reef fish species in the ocean and an atoll lagoon

In-situ behaviour of settlement-stage larvae (10–30 mm) of four coral-reef fishes – Acanthurus triostegus, Chromis viridis, Neoniphon argenteus and Ptereleotris sp. – differed between lagoon and ocean at Rangiroa Atoll, Tuamotu Islands, French Polynesia. Divers released 130 larvae individually in midwater, and recorded larval swimming speed, depth and direction. All species swam faster than average currents, and C. viridis swam faster in the lagoon than in the ocean. Vertical distribution behaviour of all species differed between ocean and lagoon, generally by larvae swimming deeper in the ocean. Nearly all individual larvae swam directionally. Within a species, distribution of average bearings of individual larvae was not directional, nor did it differ between ocean and lagoon. Larvae detected predators 3–6 m away, and stopped or changed depth or direction to avoid them. We therefore reject the 'simplifying assumptions' that reef-fish larvae are passive or that their behaviour is independent of location. Behavioural flexibility of settlement-stage reef-fish larvae has implications for dispersal, retention and population connectivity. This constitutes the first report of larval reef-fish behaviour in the open ocean. However, in the ocean, many larvae descended rapidly below safe diving depth, and adult remoras interfered, making in-situ study of larval behaviour difficult.

Reef fish behaviour during a total solar eclipse at Pinta Island, Galápagos

Diurnal fishes responded rapidly to decreased light levels during a total solar eclipse and sought shelter in the reef. Nocturnal fishes sometimes left the cover of their daytime habitats. The activity cycles of diurnal reef fishes appear to be a direct response to changes in light level.

Reef fish behaviour during a total solar eclipse at Pinta Island, Galápagos

Reef fish behaviour during a total solar eclipse at Pinta Island, Galápagos