Summary Metabolic rates of aquatic organisms are estimated from measurements oxygen consumption (ṀO2) through swimming and resting respirometry. These distinct approaches increasingly used in eco- conservation physiology studies; however, few studies have tested whether they yield comparable results. We examined two fundamental ṀO2 measures, standard metabolic rate (SMR) maximum (MMR), vary based on the method employed. Ten bridled monocle bream (Scolopsis bilineatus) were exercised using...

Abstract Tropical coral reef teleosts are exclusively ectotherms and their capacity for physical physiological performance is therefore directly influenced by ambient temperature. This study examined the effect of increased water temperature to 3 °C above on swimming metabolic 10 species damselfishes (Pomacentridae) representing evolutionary lineages from two subfamilies four genera. Five distinct measures were tested: (a) maximum speed ( U crit ), (b) gait‐transition (the at which they...

Climate change is one of the greatest threats to persistence coral reefs. Sustained and ongoing increases in ocean temperatures acidification are altering structure function reefs globally. Here, we summarise recent advances our understanding effects climate on scleractinian corals reef fish. Although there considerable among-species variability responses increasing temperature seawater chemistry, changing regimes likely have influence fish assemblages, at least over short–medium timeframes....

Previous studies hailed thermal tolerance and the capacity for organisms to acclimate adapt as primary pathways species survival under climate change. Here we challenge this theory. Over past decade, more than 365 tropical stenothermal fish have been documented moving poleward, away from ocean warming hotspots where temperatures 2-3 °C above long-term annual means can compromise critical physiological processes. We examined of a model - thermally sensitive coral reef fish, Chromis viridis...

Abstract Large‐bodied fish are critical for sustaining coral reef fisheries, but little is known about the vulnerability of these to global warming. This study examined effects elevated temperatures on movement and activity patterns common trout Plectropomus leopardus (Serranidae), which an important fishery species in tropical Australia throughout Indo West‐Pacific. Adult were collected from two locations Australia's Great Barrier Reef (23°S 14°S) maintained at one four (24, 27, 30, 33 °C)....

Respirometry is frequently used to estimate metabolic rates and examine organismal responses environmental change. Although a range of methodologies exists, it remains unclear whether differences in chamber design exercise (type duration) produce comparable results within individuals the most appropriate method differs across taxa. We repeated-measures compare estimates maximal standard (MMR SMR) four coral reef fish species using following three methods: (i) prolonged swimming traditional...

Abstract Increased ocean temperature due to climate change is raising metabolic demands and energy requirements of marine ectotherms. If productivity systems fisheries are persist, individual species must compensate for this demand through increasing acquisition or decreasing expenditure. Here we reveal that the most important coral reef fishery in Indo-west Pacific, large predatory trout Plectropomus leopardus (Serranidae), can behaviourally adjust food intake maintain body-condition under...

Abstract Tropical ectotherms are hypothesized to be vulnerable environmental changes, but cascading effects of organismal tolerances on the assembly and functioning reef fish communities largely unknown. Here, we examine differences in traits, assemblage structure, productivity cryptobenthic fishes between world’s hottest, most extreme coral reefs southern Arabian Gulf nearby, more environmentally benign, Oman. We show that assemblages half as diverse less than 25% abundant Oman, despite...

As climate-driven heat waves become more frequent and intense, there is increasing urgency to understand how thermally sensitive species are responding. Acute heating events lasting days months may elicit acclimation responses improve performance survival. However, the coordination of remains largely unknown for most stenothermal species. We documented chronology 18 metabolic cardiorespiratory changes that occur in gills, blood, spleen, muscles when tropical coral reef fishes stressed...

Energy efficiency is a key component of movement strategy for many species. In fish, optimal swimming speed (Uopt) the at which mass-specific energetic cost to move given distance minimised. Additional factors may, however, influence an individual's preferred (Upref). Activities requiring consistent sensory inputs, such as food finding, may require slower speeds than Uopt. Further, while majority fish display some form social behaviour, interactions on Upref remains unclear. It unlikely that...

Sedimentation is a substantial threat to aquatic ecosystems and primary cause of habitat degradation on near‐shore coral reefs. Although numerous studies have demonstrated major impacts sedimentation turbidity corals, virtually nothing known the sensitivity reef fishes. Planktivorous fishes are an important trophic group that funnels pelagic energy sources into ecosystems. These visual predators whose foraging likely be impaired by turbidity, but threshold for such effects their magnitude...

Rising ocean temperatures are predicted to cause a poleward shift in the distribution of marine fishes occupying extent latitudes tolerable within their thermal range boundaries. A prevailing theory suggests that upper limits constrained by hypoxia and acidification. However, some eurythermal fish species do not conform this theory, maintain hypoxia. Here we determine if same is true for stenothermal species. In three coral reef tested effect on limits, measured as critical maximum (CT max...

Abstract Climate change projections indicate more frequent and severe tropical marine heatwaves (MHWs) accompanying hypoxia year‐round. However, most studies have focused on peak summer conditions under the assumption that annual maximum temperatures will induce greatest physiological consequences. This study challenges this idea by characterizing seasonal MHWs (i.e., mean, maximum, cumulative intensities, durations, heating rates, mean occurrence) comparing metabolic traits standard rate...

Abstract The impact of ocean warming on fish and fisheries is vigorously debated. Leading theories project limited adaptive capacity tropical fishes 14-39% size reductions by 2050 due to mass-scaling limitations oxygen supply in larger individuals. Using the world’s hottest coral reefs Persian/Arabian Gulf as a natural laboratory for - where species have survived >35.0 °C summer temperatures over 6000 years are 14-40% smaller at maximum compared cooler locations we identified two pathways...

Abstract Prey individuals with complex life-histories often cannot predict the type of risk environment to which they will be exposed at each their life stages. Because level investment in defences should match local conditions, we that these have ability modulate expression an integrated defensive phenotype, but this switch occur key life-history transitions. We manipulated background juvenile damselfish for four days following settlement (a transition) or 10 post-settlement and measured a...

Current velocity in aquatic environments has major implications for the diversity, abundance and ecology of organisms, but quantifying these currents proven difficult. This study utilises a simple inexpensive instrument (<$150) to provide detailed current profile coral-reef system around Lizard Island (Great Barrier Reef, Australia) at spatial temporal scale relevant individual benthos fish. The uses load-cell sensors correlation between sensor output ambient 99%. Each is able continuously...

This study compares the critical oxygen saturation (O2 crit ) levels of shiner perch Cymatogaster aggregata obtained using two different methods wherein hypoxia is induced either by fish's respiration (closed respirometry) or degassing with nitrogen (intermittent-flow respirometry). Fish exhibited loss equilibrium at a higher O2 in closed respirometry method when compared intermittent-flow method. Utilization yielded measurements that were almost twice as high those respirometry. The lower...

Summary Unsteady water flows are common in nature, yet the swimming performance of fishes is typically evaluated at constant, steady speeds laboratory. We examined how cyclic changes flow velocity affect and energetics a labriform swimmer, shiner surfperch, Cymatogaster aggregata. Using intermittent-flow respirometry, we measured critical speed (Ucrit), oxygen consumption rate (ṀO2) pectoral fin use versus unsteady with either low (0.5 body lengths per second; BLs-1) or high amplitude (1.0...