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This study details a simple and cost-effective means of attaching acoustic transmitters to coral reef sharks and stingrays, which potentially allows for retrieval and reuse on completion of tracks. Between 2008 and 2011, galvanised timed releases were trialled in both static field tests and on blacktip reef sharks Carcharhinus melanopterus, cowtail Pastinachus atrus, and porcupine Urogymnus asperrimus rays in Coral Bay (−23°08′41″, 113°45′53″), Western Australia. The timed releases remained attached to animals for the duration required for tracking and in four out of five deployments transmitters were recovered after release from the animals. The use of modified Rototags for sharks and stainless steel darts for stingrays allowed rapid and effective attachment to animals, with limited impact on their welfare in the short term. External attachment for short-term tracking of coral reef-associated elasmobranchs should be considered as a complementary option to internal placement of transmitters in animals either by surgery or by ingestion.

Fishing and habitat degradation have increased the extinction risk of sharks, and conservation strategies recognize that survival of juveniles is critical for the effective management of shark populations. Despite the rapid expansion of marine protected areas (MPAs) globally, the paucity of shark-monitoring data on large scales (100s-1000s km) means that the effectiveness of MPAs in halting shark declines remains unclear. Using data collected by baited remote underwater video systems (BRUVS) in northwestern Australia, we developed generalized linear models to elucidate the ecological drivers of habitat suitability for juvenile sharks. We assessed occurrence patterns at the order and species levels. We included all juvenile sharks sampled and the 3 most abundant species sampled separately (grey reef [Carcharhinus amblyrhynchos], sandbar [Carcharhinus plumbeus], and whitetip reef sharks [Triaenodon obesus]). We predicted the occurrence of juvenile sharks across 490,515 km

The effects of climate change are difficult to predict for many marine species because little is known of their response to climate variations in the past. However, long-term chronologies of growth, a variable that integrates multiple physical and biological factors, are now available for several marine taxa. These allow us to search for climate-driven synchrony in growth across multiple taxa and ecosystems, identifying the key processes driving biological responses at very large spatial scales. We hypothesized that in northwest (NW) Australia, a region that is predicted to be strongly influenced by climate change, the El Nino Southern Oscillation (ENSO) phenomenon would be an important factor influencing the growth patterns of organisms in both marine and terrestrial environments. To test this idea, we analyzed existing growth chronologies of the marine fish Lutjanus argentimaculatus, the coral Porites spp. and the tree Callitris columellaris and developed a new chronology for another marine fish, Lethrinus nebulosus. Principal components analysis and linear model selection showed evidence of ENSO-driven synchrony in growth among all four taxa at interannual time scales, the first such result for the Southern Hemisphere. Rainfall, sea surface temperatures, and sea surface salinities, which are linked to the ENSO system, influenced the annual growth of fishes, trees, and corals. All four taxa had negative relationships with the Nino-4 index (a measure of ENSO status), with positive growth patterns occurring during strong La Nina years. This finding implies that future changes in the strength and frequency of ENSO events are likely to have major consequences for both marine and terrestrial taxa. Strong similarities in the growth patterns of fish and trees offer the possibility of using tree-ring chronologies, which span longer time periods than those of fish, to aid understanding of both historical and future responses of fish populations to climate variation.

Background The whale shark (Rhincodon typus Smith 1828) is the largest of the filter-feeding sharks and inhabits tropical and sub-tropical oceans worldwide. Evidence from anecdotal observations of feeding events and stomach content analysis have identified a wide range of planktonic and nektonic organisms including copepods, krill and small fish as whale shark prey. However, recent studies based on biochemical analysis (e.g. signature fatty acids (FA)) indicated that whale sharks in the western Indian Ocean had a wider foraging range than previous studies suggested, with important contributions from meso- and bathypelagic sources. However, it remains unknown if these results characterize the diet of whale sharks over the wider Indian Ocean. Here, we investigate the feeding ecology of whale sharks in the eastern Indian Ocean at Ningaloo Reef, Western Australia, by identifying differences in whale shark diet according to time of collection, sex and size-class and by examining likely food web linkages. Approach To examine whale shark feeding ecology we used signature FA analysis of both whale shark subdermal tissue and an extensive set of potential prey collected at Ningaloo Reef (Western Australia) in 2013 and 2014. Compared to other methods such as stomach content analysis, signature FA analysis provides both longer-term (up to months) dietary information and an assessment of spatial and temporal changes in the diet of predators. This is possible because some FA in animal tissues (e.g. long-chain (≥C20) polyunsaturated FA, LC-PUFA) can be used as biomarkers as they pass relatively unchanged from the low trophic levels where they are biosynthesized up the food chain. Results Whale shark sub-dermal tissue was low in lipid content (4 mg g–1 dry mass) which was dominated by phospholipids (72% of total lipid) with an energy density of 18.66 kJ g–1 dry mass. A significant intraspecific variability in whale shark FA profiles was observed resulting in four distinct groups of sharks in 2013 and five in 2014. As this variability was not related to sex or size-class, we suggest that it may be attributed to differences in the feeding habitats and thus different prey consumed by these groups of whale sharks. Variation in dietary patterns was also observed between years likely due to changes in the primary and secondary producers. Overall, examination of food web interactions showed that fatty acid profiles of whale sharks and their presumed collected prey were significantly different, suggesting that sharks fed over a wider range of habitats, including deeper waters, than we were able to access. Conclusions A significant component of whale shark diet may originate from benthic and deeper water habitats. High intraspecific variation in diet indicates that whale sharks are likely to forage over a range of distances and depths due to the challenge of inhabiting the patchy prey habitats of tropical and open ocean waters. Future studies should seek to combine signature FA analysis with other techniques such as stable isotopes, genetic and longterm tagging data to help better elucidate the feeding ecology of this iconic species.

After a pelagic larval phase, settlement-stage coral reef fish must locate a suitable reef habitat for juvenile life. Reef noise, produced by resident fish and invertebrates, provides an important cue for orientation and habitat selection during this process, which must often occur in environments impacted by anthropogenic noise. We adapted an established field-based protocol to test whether recorded boat noise influenced the settlement behavior of reef fish. Fewer fish settled to patch reefs broadcasting boat + reef noise compared with reef noise alone. This study suggests that boat noise, now a common feature of many reefs, can compromise critical settlement behavior of reef fishes.

We examined the effect of artificial light on the near shore trajectories of turtle hatchlings dispersing from natal beaches. Green turtle (Chelonia mydas) hatchlings were tagged with miniature acoustic transmitters and their movements tracked within an underwater array of 36 acoustic receivers placed in the near shore zone. A total of 40 hatchlings were tracked, 20 of which were subjected to artificial light during their transit of the array. At the same time, we measured current speed and direction, which were highly variable within and between experimental nights and treatments. Artificial lighting affected hatchling behaviour, with 88% of individual trajectories oriented towards the light and spending, on average, 23% more time in the 2.25 ha tracking array (19.5 ± 5 min) than under ambient light conditions (15.8 ± 5 min). Current speed had little to no effect on the bearing (angular direction) of the hatchling tracks when artificial light was present, but under ambient conditions it influenced the bearing of the tracks when current direction was offshore and above speeds of approximately 32.5 cm s−1. This is the first experimental evidence that wild turtle hatchlings are attracted to artificial light after entering the ocean, a behaviour that is likely to subject them to greater risk of predation. The experimental protocol described in this study can be used to assess the effect of anthropogenic (light pollution, noise, etc.) and natural (wave action, current, wind, moonlight) influences on the in-water movements of sea turtle hatchlings during the early phase of dispersal.

Background Many taxa of marine animals have increased in size through time, with some of the largest that have ever existed being vertebrate filter-feeders targeting plankton. Present day ecological studies show that the size and body structure of whale sharks is likely to reflect a strategy for gigantothermy that conserves heat while foraging in cool deep waters. However, the temperature of the oceans has changed through time, as has the composition of the guild of large, filterfeeding fishes. What do these changes reveal about the evolution and ecology of whale sharks? Approach I synthesise the results of new analyses of the fossils of filter-feeding fishes that were the largest representatives of their guild over the last 160 million years with ecological studies of whale sharks and filter-feeding whales. This analysis offers an opportunity to examine the evolutionary forces that have shaped the biology of whale sharks. Results Throughout time, bony fishes, sharks and whales that were obligate ram filter-feeders attained similar maximum lengths of around 16–20 m and in the case of the whale shark, body masses equal to, or even greater than, many baleen whales today. This shows that ecological niche and mode of feeding are more important drivers of limits to the body size of fishes than phylogeny. Conclusions The relatively small variation in maximum sizes of the largest ram filter-feeders over the last 165 million years suggests that animals within this guild will not continue to increase insize through evolutionary time, but have already attained sizes constrained by their environment and mode of feeding.

Background The seasonal aggregations of whale sharks that occur at coastal sites throughout the tropics are the focus of growing ecotourism industries. Genetic and modelling studies suggest that these aggregations may be linked by migration, although the temporal and spatial scales at which this occurs is unknown. Here, we utilized a continuously expanding photoidentification database collected by citizen scientists and researchers to assess connectivity and residency patterns of five whale shark aggregation sites across the entire Indian Ocean at timescales of up to a decade. We also investigated the effectiveness of such an approach in detecting different levels of migration given the population size at each aggregation site. Approach We used the semi-automated program I3S (Individual Interactive Identification System) to compare 6,519 photographs of the unique natural marking patterns of individual whale sharks collected from aggregations at Mozambique, the Seychelles, the Maldives, Christmas Island (Australia) and Ningaloo Reef (Australia). We searched the database for matches between aggregations (migration) and matches between years within aggregations (residency). A Monte Carlo simulation approach utilizing population sizes of aggregations reported by previous studies was used to examine the sample sizes that would be required to reliably detect varying levels of migration rates among four of these aggregations. Results We found no evidence of connectivity of whale shark aggregations at ocean-basin scales within the time frame of the study, and evidence for only limited connectivity at regional (100s–1000s km) scales. A male whale shark sampled in January 2010 at Mozambique was resighted eight months later in the Seychelles and was the only one of 1,724 individuals to be photographed at more than one site. On average, 35% of individuals were re-sighted at the same site in more than one year. The Monte Carlo simulation study showed that the power of this photo-identification approach was strongly dependent on both the number of individuals identified in aggregations each year and the size of resident populations. The simulation also indicated that there was a higher chance of detecting migrants (if they were present) in aggregations at Ningaloo Reef and the Maldives than the Seychelles and Mozambique given the current numbers of individuals identified each year. Conclusions The weight of evidence from both our photo-identification study and previous tagging studies suggests regional or small-scale movements (10–100s km) may be more common in whale sharks than movement at ocean-basin scales. We recommend that the management of whale sharks in the Indian Ocean occur at regional scales, and photo-identification databases are expanded to include additional sampling sites within each region.

Genetic and modelling studies suggest that seasonal aggregations of whale sharks ( Rhincodon typus ) at coastal sites in the tropics may be linked by migration. Here, we used photo-identification (photo-ID) data collected by both citizen scientists and researchers to assess the connectedness of five whale shark aggregation sites across the entire Indian Ocean at timescales of up to a decade. We used the semi-automated program I 3 S (Individual Interactive Identification System) to compare photographs of the unique natural marking patterns of individual whale sharks collected from aggregations at Mozambique, the Seychelles, the Maldives, Christmas Island (Australia) and Ningaloo Reef (Australia). From a total of 6519 photos, we found no evidence of connectivity of whale shark aggregations at ocean-basin scales within the time frame of the study and evidence for only limited connectivity at regional (hundreds to thousands of kilometres) scales. A male whale shark photographed in January 2010 at Mozambique was resighted eight months later in the Seychelles and was the only one of 1724 individuals in the database to be photographed at more than one site. On average, 35% of individuals were resighted at the same site in more than one year. A Monte Carlo simulation study showed that the power of this photo-ID approach to document patterns of emigration and immigration was strongly dependent on both the number of individuals identified in aggregations and the size of resident populations.

Hays, Graeme C. et al., It is a golden age for animal movement studies and so an opportune time to assess priorities for future work. We assembled 40 experts to identify key questions in this field, focussing on marine megafauna, which include a broad range of birds, mammals, reptiles, and fish. Research on these taxa has both underpinned many of the recent technical developments and led to fundamental discoveries in the field. We show that the questions have broad applicability to other taxa, including terrestrial animals, flying insects, and swimming invertebrates, and, as such, this exercise provides a useful roadmap for targeted deployments and data syntheses that should advance the field of movement ecology., Workshop funding was granted to M.T., A.M.M.S., and C.M.D. by the UWA Oceans Institute, the Australian Institute of Marine Science, and the Office of Sponsored Research at King Abdullah University of Science and Technology (KAUST).

Long-term vital rate and life-history data essential for sustainable harvest management are rare in tropical fisheries. Two commercially important shark species, Australian blacktip ( Carcharhinus tilstoni ) and spot-tail ( C. sorrah ) sharks in northern Australia have changed in size and population status over the last 25 years. These populations were exploited heavily from the early 1970s to the mid-1980s by foreign fishers, and since then have been harvested by a relatively small domestic fishery. We examined the differences in fork length of these species caught in 1983–1985 and 2002–2006 using Bayesian forms of generalised linear and mixed-effects models. We found clear regional differences and changes in size over time. For blacktips, sharks from the Gulf of Carpentaria have become smaller, and those from the western Northern Territory, larger over time. For spot-tail sharks, average size increased from the 1980s in the Gulf of Carpentaria, but not in the western Northern Territory. On average, sharks from the Gulf of Carpentaria were larger than those on the west coast of the Northern Territory, and females were larger than males. We suggest that changes over time and between regions in the size of spot-tail sharks are most likely due to over-exploitation in the past and subsequent recovery of populations. We discuss the uncertainty in trends for blacktip sharks in relation to fishing effort, availability of resources and species identification errors.

Photo-identification and conventional tagging were used to estimate population size and structure of the whale shark Rhincodon typus near Holbox Island, Mexico. From 2005 to 2008, photographs of spot patterns behind the last gill slit and in a lateral view on the left side of each animal were used to identify individuals. Additionally, 578 R. typus were tagged using conventional marker tags. Of these and the 350 R. typus that were identified from 1184 photographs, 65% were male; 27%, female and 8%, indeterminate sex. Photographed R. typus ranged in size from 2·5 to 9·5 m total length. Size was bimodal with a large peak at 6 m and a smaller peak at 7 m. Photo-identification showed that there was considerable loss of marker tags. Few of these remained on the animals for more than a year, so that interannual re-sights using tagging could not be used in population modelling. Forty six interannual re-sightings were found in the photographic library; the interval between these re-sightings was typically 1 year. It was estimated that the R. typus aggregation near Holbox Island ranged from 521 to 809 individuals, based on mark-recapture models. From 13 to 33% of R. typus photographed had scars that were attributable to boat strikes. This study provides a baseline for assessing the status of R. typus near Holbox Island. This information is useful to understand drivers of local population size and distribution and potential concerns about increasing effects of tourism on R. typus in this area and for designing better management programmes for R. typus conservation.

1. With the global increase in CO2 emissions, there is a pressing need for studies aimed at understanding the effects of ocean acidification on marine ecosystems. Several studies have reported that exposure to CO2 impairs chemosensory responses of juvenile coral reef fishes to predators. Moreover, one recent study pointed to impaired responses of reef fish to auditory cues that indicate risky locations. These studies suggest that altered behaviour following exposure to elevated CO2 is caused by a systemic effect at the neural level. 2. The goal of our experiment was to test whether juvenile damselfish Pomacentrus amboinensis exposed to different levels of CO2 would respond differently to a potential threat, the sight of a large novel coral reef fish, a spiny chromis, Acanthochromis polyancanthus, placed in a watertight bag. 3. Juvenile damselfish exposed to 440 (current day control), 550 or 700 μatm CO2 did not differ in their response to the chromis. However, fish exposed to 850 μatm showed reduced antipredator responses; they failed to show the same reduction in foraging, activity and area use in response to the chromis. Moreover, they moved closer to the chromis and lacked any bobbing behaviour typically displayed by juvenile damselfishes in threatening situations. 4. Our results are the first to suggest that response to visual cues of risk may be impaired by CO2 and provide strong evidence that the multi-sensory effects of CO2 may stem from systematic effects at the neural level.

Predicted future CO2 levels can affect reproduction, growth, and behaviour of many marine organisms. However, the capacity of species to adapt to predicted changes in ocean chemistry is largely unknown. We used a unique field-based experiment to test for differential survival associated with variation in CO2 tolerance in a wild population of coral-reef fishes. Juvenile damselfish exhibited variation in their response to elevated (700 μatm) CO2 when tested in the laboratory and this influenced their behaviour and risk of mortality in the wild. Individuals that were sensitive to elevated CO2 were more active and move further from shelter in natural coral reef habitat and, as a result, mortality from predation was significantly higher compared with individuals from the same treatment that were tolerant of elevated CO2. If individual variation in CO2 tolerance is heritable, this selection of phenotypes tolerant to elevated CO2 could potentially help mitigate the effects of ocean acidification.

Determining how prey learn the identity of predators and match their vigilance with current levels of threat is central to understanding the dynamics of predator–prey systems and the determinants of fitness. Our study explores how feeding history influences the relative importance of olfactory and visual sensory modes of learning, and how the experience gained through these sensory modes influences behaviour and survival in the field for a juvenile coral reef damselfish. We collected young fish immediately prior to their settlement to benthic habitats. In the laboratory, these predator-naïve fish were exposed to a high- or low-food ration and then conditioned to recognize the olfactory cues (odours) and/or visual cues from two common benthic predators. Fish were then allowed to settle on reefs in the field, and their behaviour and survival over 70 h were recorded. Feeding history strongly influenced their willingness to take risks in the natural environment. Conditioning in the laboratory with visual, olfactory or both cues from predators led fish in the field to display risk-averse behaviour compared with fish conditioned with sea water alone. Well-fed fish that were conditioned with visual, chemical or a combination of predator cues survived eight times better over the first 48 h on reefs than those with no experience of benthic predator cues. This experiment highlights the importance of a flexible and rapid mechanism of learning the identity of predators for survival of young fish during the critical life-history transition between pelagic and benthic habitats.

Arguments for conservation of sharks based on their role in the maintenance of healthy marine ecosystems have failed to halt the worldwide decline in populations. Instead, the value of sharks as a fishery commodity has severely reduced the abundance of these animals. Conservation may be assisted by the development of an alternative approach that emphasizes the economic value of sharks as a non-harvested resource. Our study quantifies the value of a tourism industry based on shark diving. Using data collected from surveys, as well as government statistics, we show that shark diving is a major contributor to the economy of Palau, generating US$18 million per year and accounting for approximately 8% of the gross domestic product of the country. Annually, shark diving was responsible for the disbursement of US$1.2 million in salaries to the local community, and generated US$1.5 million in taxes to the government. If the population of approximately 100 sharks that interact with tourists at popular dive sites was harvested by fishers, their economic value would be at most US$10 800, a fraction of the worth of these animals as a non-consumptive resource. Fishers earn more selling fish for consumption by shark divers than they would gain by catching sharks. Shark diving provides an attractive economic alternative to shark fishing, with distribution of revenues benefiting several sectors of the economy, stimulating the development and generating high revenues to the government, while ensuring the ecological sustainability of shark populations.

Taylor's Power Law for the temporal fluctuation in population size (TL) posits that the variance in abundance scales according to aM(b); where M is the mean abundance and a and b are the 'proportionality' and 'scaling' coefficients. As one of the few empirical rules in population ecology, TL has attracted substantial theoretical and empirical attention. Much of this attention focused on the scaling coefficient; particularly its ubiquitous deviation from the null value of 2. Here we present a line of reasoning that challenges the power-law interpretation of the empirical log-linear relationship between the mean and variance of population size. At the core of our reasoning is the proposition that populations vary not only with respect to M but also with respect to a; which leaves the log-linear relationship intact but forfeits its power-law interpretation. Using the stochastic logistic-growth model as an example, we show that ignoring among-population variation in a is akin to ignoring the variation in the intrinsic rate of growth (r). Accordingly, we show that the slope of the log-linear relationship (b) is a function of the among-population (co)variation in r and the carrying-capacity. We further demonstrate that local environmental stochasticity is sufficient to generate the full range of observed values of b, and that b can in fact be insensitive to substantial differences in the balance between variance-generating and stabilizing processes.

After a pelagic larval phase, settlement-stage coral reef fish must locate a suitable reef habitat for juvenile life. Reef noise, produced by resident fish and invertebrates, provides an important cue for orientation and habitat selection during this process, which must often occur in environments impacted by anthropogenic noise. We adapted an established field-based protocol to test whether recorded boat noise influenced the settlement behavior of reef fish. Fewer fish settled to patch reefs broadcasting boat + reef noise compared with reef noise alone. This study suggests that boat noise, now a common feature of many reefs, can compromise critical settlement behavior of reef fishes.

Establishing the ecological role of predators within an ecosystem is central to understanding community dynamics and is useful in designing effective management and conservation strategies. We analysed differences in the trophic ecology of four species of reef sharks (Carcharhinus melanopterus, Carcharhinus amblyrhynchos, Triaenodon obesus and Negaprion acutidens) at Ningaloo Reef, Western Australia, by analysing tissue stable isotopes (δ15N and δ13C). We also monitored animals using acoustic telemetry to determine long-term residency patterns in a bay at the southern end of the reef, Coral Bay. Overall, mean δ13C was similar among species, ranging between −10.9 and −11.8‰, suggesting a food-web dependency on coastal producers. Classification and regression tree analysis identified an effect of species on δ15N that separated C. amblyrhynchos and C. melanopterus from N. acutidens and T. obesus. For C. amblyrhynchos and C. melanopterus, animals were also divided by size classes, with smaller sharks having lower average δ15N than larger animals; this suggests that δ15N increases with size for these two species. Juvenile C. melanopterus, juvenile N. acutidens and adult T. obesus had trophic levels of 3.7, for juvenile C. amblyrhynchos and adult C. melanopterus it was 4, and adult C. amblyrhynchos had a value of 4.3. Trophic-level estimates for C. melanopterus and C. amblyrhynchos corroborate previous conclusions based on diet studies. We found no evidence for a difference in isotopic composition between resident and non-resident sharks. The lack of variation in isotopic composition was consistent with high mean residency of these species recorded using acoustic telemetry, which was 79% (±0.09 SE) of days monitored for T. obesus, followed by N. acutidens (57 ± 19.55%), C. amblyrhynchos (54 ± 13%) and C. melanopterus (33 ± 8.28%). High δ13C composition in reef sharks and long-term residency behaviour suggest that coastal marine reserves might provide effective conservation refuges for some species.

Aim Predicting distribution patterns of whale sharks (Rhincodon typus, Smith 1828) in the open ocean remains elusive owing to few pelagic records. We developed multivariate distribution models of seasonally variant whale shark distributions derived from tuna purse-seine fishery data. We tested the hypotheses that whale sharks use a narrow temperature range, are more abundant in productive waters and select sites closer to continents than the open ocean. Location Indian Ocean. Methods We compared a 17-year time series of observations of whale sharks associated with tuna purse-seine sets with chlorophyll a concentration and sea surface temperature data extracted from satellite images. Different sets of pseudo-absences based on random distributions, distance to shark locations and tuna catch were generated to account for spatiotemporal variation in sampling effort and probability of detection. We applied generalized linear, spatial mixed-effects and Maximum Entropy models to predict seasonal variation in habitat suitability and produced maps of distribution. Results The saturated generalized linear models including bathymetric slope, depth, distance to shore, the quadratic of mean sea surface temperature, sea surface temperature variance and chlorophyll a had the highest relative statistical support, with the highest percent deviance explained when using random pseudo-absences with fixed effect-only models and the tuna pseudo-absences with mixed-effects models (e.g. 58% and 26% in autumn, respectively). Maximum Entropy results suggested that whale sharks responded mainly to variation in depth, chlorophyll a and temperature in all seasons. Bathymetric slope had only a minor influence on the presence. Main conclusions Whale shark habitat suitability in the Indian Ocean is mainly correlated with spatial variation in sea surface temperature. The relative influence of this predictor provides a basis for predicting habitat suitability in the open ocean, possibly giving insights into the migratory behaviour of the world’s largest fish. Our results also provide a baseline for temperature-dependent predictions of distributional changes in the future.

Little is known about the impact of ocean acidification on predator–prey dynamics. Herein, we examined the effect of carbon dioxide (CO2) on both prey and predator by letting one predatory reef fish interact for 24 h with eight small or large juvenile damselfishes from four congeneric species. Both prey and predator were exposed to control or elevated levels of CO2. Mortality rate and predator selectivity were compared across CO2 treatments, prey size and species. Small juveniles of all species sustained greater mortality at high CO2 levels, while large recruits were not affected. For large prey, the pattern of prey selectivity by predators was reversed under elevated CO2. Our results demonstrate both quantitative and qualitative consumptive effects of CO2 on small and larger damselfish recruits respectively, resulting from CO2-induced behavioural changes likely mediated by impaired neurological function. This study highlights the complexity of predicting the effects of climate change on coral reef ecosystems.

We examine the structure and phylogeography of the pig-eye shark (Carcharhinus amboinensis) common in shallow coastal environments in northern Australia using two types of genetic markers, two mitochondrial (control region and NADH hydrogenase 4) and two nuclear (microsatellite and Rag 1) DNA. Two populations were defined within northern Australia on the basis of mitochondrial DNA evidence, but this result was not supported by nuclear microsatellite or Rag 1 markers. One possibility for this structure might be sex-specific behaviours such as female philopatry, although we argue it is doubtful that sufficient time has elapsed for any potential signatures from this behaviour to be expressed in nuclear markers. It is more likely that the observed pattern represents ancient populations repeatedly isolated and connected during episodic sea level changes during the Pleistocene epoch, until current day with restricted contemporary gene flow maintaining population genetic structure. Our results show the need for an understanding of both the history and ecology of a species in order to interpret patterns in genetic structure.

We compare vertebral microchemistry with previously described age-related movement patterns of bull sharks Carcharhinus leucas and pig-eye sharks C. amboinensis within coastal waters of north Australia. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) quan- tified the chemical signatures of nursery habitats within the vertebrae of juvenile and adult sharks. We examined evidence for adults returning to these habitats by applying LA-ICP-MS along a growth axis of their vertebrae. We transposed chemical signatures with growth increments in adult vertebrae to correlate with age estimates. Unique elemental signatures were identified in each of the fresh - water nurseries, but we did not find them in adult vertebrae. Age-specific changes in vertebral micro- chemistry in mature female bull sharks correlate with periodic returns every 1 to 2 yr to less saline environments to pup. We were unable to discriminate among natal habitats of pig-eye sharks using elemental fingerprints, and age-specific changes in vertebral microchemistry were also absent. We conclude that changes in vertebral microchemistry correlate with known habitat use patterns of the bull and pig-eye sharks, showing the potential of vertebral microchemistry to discern movement patterns in sharks.

The quantification of spatial and temporal movement patterns of coral reef sharks is im- portant to understand their role in reef communities and to aid the design of conservation strategies for this predatory guild. We observed 4 species of reef sharks aggregating in an inshore bay in the north of Western Australia for over 2 yr, using acoustic telemetry and visual censuses to examine how they par- titioned this site in space and time. We fitted 58 sharks with acoustic transmitters: Carcharhinus melanopterus (36), C. amblyrhynchos (11), Negaprion acutidens (7) and Triaenodon obesus (4). Aggre- gations consisted primarily of C. melanopterus, although C. amblyrhynchos and N. acu tidens were of- ten present. We observed aggregations by visual census in summer (maximum of 44 sharks). Detec- tions were highest during warmer months (Sep to Mar) for all species, although some individuals showed year-round residency. C. melanopterus, C. amblyrhynchos and N. acutidens had strong diel patterns of attendance at the aggregation site. Peak daily detections occurred from 13:00 to 14:00 h local time for C. melanopterus and C. amblyrhynchos; juvenile C. melanopterus and N. acutidens peaked at 05:00 and 10:00 h, respectively. There was considerable spatial overlap of core areas of use (50% kernel density estimates) at the northern end of the bay by all species; the southern end was used primarily by C. melanopterus and N. acutidens. Aggregations of C. mela nop terus and C. am- blyrhynchos consisted mainly of adult females, some of them pregnant. Courtship behaviour in C. melanopterus and T. obesus suggests that these aggregations are related to reproduction. All species displayed inter-annual site fidelity. The long-term presence of juvenile C. melanopterus and N. acuti- dens also suggests that this bay provides suitable conditions for younger age classes.

Our planet is experiencing an increase in the concentration of atmospheric carbon dioxide (CO2) unprecedented in the past 800 000 years. About 30% of excess atmospheric CO2 is absorbed by the oceans, thus increasing the concentration of carbonic acid and reducing the ocean's pH. Species able to survive the physiological stress imposed by ocean acidification may still suffer strong indirect negative consequences. Comparing the tolerance of different species to dissolved CO2 is a necessary first step towards predicting the ecological impacts of rising CO2 levels on marine communities. While it is intuitive that not all aquatic species will be affected the same way by CO2, one could predict that closely related species, sharing similar life histories and ecology, may show similar tolerance levels to CO2. Our ability to create functional groups of species according to their CO2 tolerance may be crucial in our ability to predict community change in the future. Here, we tested the effects of CO2 exposure on the antipredator responses of four damselfish species (Pomacentrus chrysurus, Pomacentrus moluccensis, Pomacentrus amboinensis and Pomacentrus nagasakiensis). Although being sympatric and sharing the same ecology and life history, the four congeneric species showed striking and unexpected variation in CO2 tolerance, with CO2-induced loss of response to predation risk ranging from 30% to 95%. Using P. chrysurus as a model species, we further tested if these behavioural differences translated into differential ability to survive predators under natural conditions. Our results indicate that P. chrysurus larvae raised under CO2 levels predicted by 2070 and 2100 showed decreased antipredator responses to risk, leading to a five- to sevenfold increase in predation-related mortality in the first few hours of settlement. Examining ocean acidification, along with other environmental variables, will be a critical step in further evaluating ecological responses to predicted climatic change.

Grey reef sharks (Carcharhinus amblyrhynchos) are apex predators found on many Indo-Pacific coral reefs, but little is known about their movement patterns and habitat requirements. We used acoustic telemetry to determine movements and habitat use of these sharks at the isolated Rowley Shoals atolls, 250 km off the coast of north-western Australia. We equipped 12 male and 14 female sharks ranging from 0.79 to 1.69 m in total length with transmitters that were detected by an array of 11 strategically placed receivers on two atoll reefs. Over 26,000 detections were recorded over the 325 days of receiver deployment. No sharks were observed to move between reefs. Receivers on the outer slopes of reefs provided nearly all (99%) of the detections. We found no differences in general attendance parameters due to size, sex or reef, except for maximum period of detection where larger sharks were detected over a longer period than smaller sharks. Male and female sharks were often detected at separate receivers at the outer slope habitat of one reef, suggesting sexual segregation, but this pattern did not occur at the second reef where males and females were detected at similar frequencies. We identified two patterns of daily behaviour: (1) sharks were present at the reef both day and night or (2) sharks spent more time in attendance during day than at night. Fast Fourier transforms identified 24-h cycles of attendance at the reef and a secondary peak of attendance at 12 h for most sharks, although no individuals shared the same attendance patterns. Our study provides baseline data that can be used to optimise the minimum area and habitat requirements for conservation of these apex predators.

Increasing ocean temperatures due to global warming are predicted to have negative effects on coral reef fishes. El Nino events are associated with elevated water temperatures at large spatial (1000s of km) and temporal (annual) scales, providing environmental conditions that enable temperature effects on reef fishes to be tested directly. We compared remote sensing data of sea surface temperature (SST) anomalies, surface current flow and chlorophyll-a (Chl-a) concentration with monthly patterns in larval supply of coral reef fishes in nearshore waters around Rangiroa Atoll (French Polynesia) from January 1996 to March 2000. This time included an intense El Nino (April 1997-May 1998) event between two periods of La Nina (January-March 1996 and August 1998-March 2000) conditions. There was a strong relationship between the timing of the El Nino event, current flow, ocean productivity (as measured by Chl-a) and larval supply. In the warm conditions of the event, there was an increase in the SST anomaly index up to 3.51C above mean values and a decrease in the strength of the westward surface current toward the reef. These conditions coincided with low concentrations of Chl-a (mean: 0.06 mg m � 3 ,S E� 0.004) and a 51% decline in larval supply from mean values. Conversely, during strong La Nina conditions when SST anomalies were almost 21C below mean values and there was a strong westward surface current, Chl-a concentration was 150% greater than mean values and larval supply was 249% greater. A lag in larval supply suggested that productivity maybe affecting both the production of larvae by adults and larval survival. Our results suggest that warming temperatures in the world's oceans will have negative effects on the reproduction of reef fishes and survival of their larvae within the plankton, ultimately impacting on the replenishment of benthic populations.

Individual growth patterns in ecology are often determined from population field data through the use of regression and model selection inference analyses. However, such approaches are typically unable to provide insight into dynamic processes when based upon collections of ‘snapshot’ data that consist of only a single observation for each individual. We caution how model selection inference from size-at-age data may lead to growth models that are mis-specified in the case of species such as squid and fishes that display fast and variable growth and for which, field data of the early part of the lifespan are typically sparse and difficult to obtain.

There is increasing concern that ocean acidification, caused by the uptake of additional CO 2 at the ocean surface, could affect the functioning of marine ecosystems; however, the mechanisms by which population declines will occur have not been identified, especially for noncalcifying species such as fishes. Here, we use a combination of laboratory and field-based experiments to show that levels of dissolved CO 2 predicted to occur in the ocean this century alter the behavior of larval fish and dramatically decrease their survival during recruitment to adult populations. Altered behavior of larvae was detected at 700 ppm CO 2 , with many individuals becoming attracted to the smell of predators. At 850 ppm CO 2 , the ability to sense predators was completely impaired. Larvae exposed to elevated CO 2 were more active and exhibited riskier behavior in natural coral-reef habitat. As a result, they had 5–9 times higher mortality from predation than current-day controls, with mortality increasing with CO 2 concentration. Our results show that additional CO 2 absorbed into the ocean will reduce recruitment success and have far-reaching consequences for the sustainability of fish populations.

Settlement from the plankton ends the major dispersive stage of life for many marine organisms and exposes them to intense predation pressure in juvenile habitats. This predation mortality represents a life-history bottleneck that can determine recruitment success. At the level of individual predator-prey interactions, prey survival depends upon behavior, specifically how behavior affects prey conspicuousness and evasive ability. We conducted an experiment to identify behavioral traits and performance levels that are important determinants of which individuals survive or die soon after settlement. We measured a suite of behavioral traits on late stage, pre-settlement Ward's damsel (Pomacentrus wardi) collected using light traps. These behavioral traits included two measures of routine swimming (indicators of conspicuousness) and eight measures of escape performance to a visual startle stimulus. Fish were then released onto individual patch reefs, where divers measured an additional behavioral trait (boldness). We censused each patch reef until approximately 50% of the fish were missing (~24 h), which we assumed to be a result of predation. We used classification tree analysis to discriminate survivors from fish presumed dead based on poor behavioral performance. The classification tree revealed that individuals displaying the maladaptive combination of low escape response speed, low boldness on the reef, and high routine swimming speed were highly susceptible to predation (92.4% with this combination died within 24 h). This accounted for 55.2% of all fish that died. Several combinations of behavioral traits predicted likely survival over 24 h, but there was greater uncertainty about that prediction than there was for fish that were predicted to die. Thus maladaptive behavioral traits were easier to identify than adaptive traits.

Seven whale sharks were tracked using satellite-linked tags from Ningaloo Reef, off northern Western Australia, following tagging in April and June 2002 and April–May 2005. We investigated how the movements of those whale shark tracks were influenced by geostrophic surface currents during sequential one-week periods by using a passive diffusion model parameterised with observed starting locations of the sharks and weekly maps of surface current velocity and direction (derived from altimetry). We compared the outputs from the passive diffusion model and maps of chlorophyll-a concentration (SeaWiFs/MODIS) and with the actual tracks of the sharks using GIS and generalized linear mixed-effects models (GLMM). The GLMM indicated very little support for passive diffusion with sea-surface ocean currents influencing whale shark distributions in the north eastern Indian Ocean. Moreover, the sharks' movements correlated only weakly with the spatial distribution of sea-surface chlorophyll-a concentrations. The seven whale sharks had average swimming speeds comparable with those recorded in other satellite tracking studies of this species. Swimming speeds of the seven sharks were similar to those reported in previous studies and up to three times greater than the maximum sea-surface current velocities that the sharks encountered while traversing into lower southerly latitudes (moving northward towards the equator). Our results indicate that whale sharks departing from Ningaloo travel actively and independently of near-surface currents where they spend most of their time despite additional metabolic costs of this behaviour.

Global declines of shark populations are of concern because of their largely assumed role as moderators of ecosystem function. Without long-term data on movement patterns for many species, it is impossible to infer relative extinction risk, which varies as a function of range, dispersal and habitat specificity and use. The past 50 yr of research on coastal sharks has revealed common movement patterns among species. In the horizontal plane, measured home range size generally increases with body size. We demonstrate meta-analytically the effects of increasing body size and monitoring time on home range size. Changes in the extent of horizontal movement might arise from ontogeny, predator avoidance or environmental tolerances. In the vertical plane, movement patterns include oscillatory vertical displacement, surface swimming, diel vertical migration and swimming at depth. These vertical movements are often attributed to foraging or navigation, but have been quan- tified less than horizontal patterns. Habitat specificity is often correlated with environmental condi- tions such as depth, salinity, substratum, and in some cases, prey availability. Site fidelity is common in species that use nursery areas. However, fidelity to mating, pupping, feeding and natal sites has only been observed in a few species. To date, few studies have examined habitat partitioning, although some general patterns have emerged: habitats appear to be subdivided by benthos type, prey availability and depth. The conservation of coastal sharks can be facilitated in some cases by the use of marine protected areas, especially for coastal resident species using specific nursery, repro- duction or feeding areas. Partial protected-area closures might be effective during aggregation or migration periods to protect older size classes, but these must be applied with other management strategies such as reduced fishing and size or bag limits to protect individuals throughout different life history phases. More long-term research on habitat use, migration patterns and habitat partition- ing is essential for developing successful management initiatives for coastal shark populations.

Behavioural traits can strongly influence fitness and survival and are important mediators of life history trade-offs. This study explored the links between mortality trade-offs associated with fast growth during larval life and behaviour of individuals during an important life history transition. Longitudinal sampling of a cohort of damselfish settling on a reef at the end of their larval stage found that individuals with small otolith sizes at hatching and low otolith growth rates were selectively removed from the local population, while there was no apparent selection for size or body condition over the first 24 h after settlement. Selection against slow growth (initial larval growth and maximum growth) and small size at hatching and settlement were accentuated over the first month after settlement. Detailed behavioural assessments of naive larvae settled onto habitat patches and monitored for 24 h found that initial boldness aided survival, but individuals that ventured larger distances from shelter suffered higher mortality. Correlations of growth with behavioural attributes were generally poor; however, there was a weak correlation between boldness and maximum growth. A measure of flexibility in the maximum distance ventured from shelter was positively related to initial otolith growth. Our results suggest that although early growth which is relatively slow leads to higher mortality later in life, and behavioural attributes influenced survival, there were only weak correlations between growth history and behaviour. This may be due to strong selective pressures on young fish to learn novel behaviours rapidly after settlement. Selection may promote behavioural flexibility at this key ecological transition.

Trade-offs between the costs and benefits of growth are thought to be mediated by behaviour, whereby rapid growth is associated with greater predation mortality because of increased foraging effort. We tested this hypothesis by collecting young Pomacentrus amboinensis using light traps and settling them onto patch reefs where their behaviour and survivorship were monitored for 24 h. One month later, individuals of the same cohort were collected from shallow reefs and released onto patch reefs where their behaviour and survivorship were monitored for 6 days. At settlement young fish suffered high (60% in 24 h) mortality that preferentially removed larger, faster-growing individuals. However, we could find no evidence that foraging behaviour contributed to this selective mortality. In contrast, 1 month later the same cohort underwent negative size-selective mortality where the smallest, slower-growing fish were preferentially removed by predators. Larger fish spent more time foraging, were more aggressive, swam greater distances and chased more fish than smaller individuals. Thus, consistent individual differences in behaviour contributed to patterns of mortality, but in a way that involved no apparent trade-off with growth. For P. amboinensis, consistent variation in growth may be maintained by spatial and temporal differences in the selective regime within the reef environment.

Funding was provided by the Australian Commonwealth Environment Research Facilities (CERF) programme (partners include the University of Tasmania, CSIRO, Geoscience Australia, the Australian Institute of Marine Science and Museum Victoria). We thank all members of the Australian Institute of Marine Science Long-Term Monitoring Program who have contributed to data collection. We are grateful to B. Venables, R. Pitcher, N. Bax and M. Hughes for their insights and suggestions.

In 2017, the Australian Institute of Marine Science and its partners commenced the North West Shoals to Shore Research Program. The program is designed to address significant scientific and environmental knowledge gaps pertinent to the management of the offshore petroleum industry, a key stakeholder in this ecologically and commercially important region of Australia. The program comprises four themes. 1. Marine noise monitoring and impacts: includes two seismic source (2600 cubic inch air-gun array) exposure experiments have been conducted to investigate selected responses by demersal fishes and pearl oysters across different spatial and temporal scales. 2. Seabed habitats and demersal biodiversity: seeks to understand the physical and biological characteristics of the ancient coastline key ecological feature around the 125 m depth contour and pearl oyster habitats offshore from Eighty Mile Beach. The work examines the ecological processes that maintain benthic communities on both ancient and contemporary coastlines 3. Protected and iconic species movement, distribution and threats: uses innovative sampling techniques to confirm biologically important areas for pygmy blue whales, hawksbill and green turtles. This will assist the quantification and mitigation of the risks vessel movements, industrial infrastructure and activities pose to marine megafauna on the Northwest Shelf. 4. Spatial dynamics of isolated coral reef atolls: develops a habitat model and adaptive monitoring program that informs the future condition of these remote coral reef atolls. Significant progress has been made by the program in 2018, including the development of innovative and technical approaches to sampling.

Animals use many different cues to orient in their environment, solve directional movement challenges, and select suitable habitat. Recent work has highlighted the importance of the ambient soundscape in providing orientation cues for larvae of coral reef fishes at the key life-history phase when they recruit from open ocean to coral reef environments. In this study, we combined acoustic conditioning with binary choice chambers and used 442 settlement-stage larvae from 4 Pomacentridae (damselfish) species (Pomacentrus amboinensis, P. brachialis, P. moluccensis, and P. nagasakiensis) to test whether responses to acoustic cues are fixed or whether behavior is influenced by recent acoustic experience. Over 8 trials, groups of wild-caught larvae that experienced noise (natural reef noise or artificial tone noise) during a 12-h conditioning period showed a positive directional response to reef noise in the chambers. Groups conditioned with reef noise responded adversely to the tone noise, whereas groups conditioned to the artificial tones were subsequently attracted by them. This plasticity in behavior suggests that settlement-stage larval reef fish (;20 days old) are influenced by, and can retain information from, recent acoustic experiences. Behavioral plasticity may enable greater control by larvae over their selection of settlement sites but could also mean that anthropogenic sounds have more than masking effects on the orientation behavior of fishes. Key words: acoustic cues, choice chambers, coral reef fishes, orientation, Pomacentridae. [Behav Ecol]

Seasonal observations of whale shark abundance recorded by ecotourist operators at Ningaloo Reef, Western Australia from 1999 to 2004 were compared with weekly regional and global oceanographic and atmospheric variables, including average sea surface temperatures, along-shelf wind shear, sea level and the Southern Oscillation Index (SOI). Estimates of these physical variables were derived from either ground-based data or from remote sensing instruments. A generalised linear mixed-effects modelling (GLMM) approach with random sampling and model simulation was used to determine the relationships between the number of whale sharks and all model variants of the environmental parameters, using information-theoretic weights of evidence to rank models. SOI and wind shear had the most support for explaining the deviance in weekly whale shark abundance at Ningaloo Reef during a season. The SOI and wind shear variables positively influenced whale shark abundance such that more sharks were sighted when the Southern Oscillation was stronger and along-shelf winds were increasingly prevalent. This may reflect changes in the strength of oceanographic processes such as the Leeuwin Current (in response to the Southern Oscillation) and wind/current driven upwelling which may affect the abundance of whale sharks transported to the region and/or the availability of their prey by driving productivity changes.

To determine whether enhancing the survival of new recruits is a sensible target for the restorative management of depleted coral-reef fish populations, settlement-stage ambon damsel fish Pomacentrus amboinensis were captured, tagged and then either released immediately onto small artificial reefs or held in aquaria for 1 week prior to release. Holding conditions were varied to determine whether they affected survival of fish: half the fish were held in bare tanks (non-enriched) and the other half in tanks containing coral and sand (enriched). Holding fish for this short period had a significantly positive effect on survivorship relative to the settlement-stage treatment group that were released immediately. The enrichment of holding conditions made no appreciable difference on the survival of fish once released onto the reef. It did, however, have a positive effect on the survival of fish while in captivity, thus supporting the case for the provision of simple environmental enrichment in fish husbandry. Collecting and holding settlement-stage fish for at least a week before release appear to increase the short-term survival of released fish; whether it is an effective method for longer-term enhancement of locally depleted coral-reef fish populations will require further study.

Illegal, unreported and unregulated (IUU) fishing can lead to irreversible ecosystem changes; however, it is also one of the most difficult forms of fishing to manage and deter. In northern Australia over the past decade there has been a large increase in small-scale IUU fishing. We suggest that this small-scale fishing has arisen because of long-term fisheries over-exploitation in South East Asia. This IUU fishing forms part of the expansion-and-displacement cycle that can rapidly reduce biomass and alter the trophic structure of local ecosystems. With increasing human populations in the region, the pressure to fish illegally is likely to increase. Regional responses are required to deter and monitor the illegal over-exploitation of fisheries resources, which is critical to secure ecosystem stability as climate change and other destructive human activities threaten food security.

Multiple internal and external tagging experiments tested the applicability of five back-calculation models (Biological Intercept, Modified-Fry, Body Proportional Hypothesis, Time-Varying Growth, and an Age-Effects model) as predictors of individual growth trajectories of two marine cleaning gobies, Elacatinus evelynae and E. prochilos, that were raised in aquaria under conditions that resulted in variable growth. Mixed-effect model analyses of longitudinal records of otoliths and somatic growth collected at the individual level revealed that E. evelynae and E. prochilos produced daily increments on their otoliths for up to two months post-settlement and that the Modified-Fry model provided the most accurate size-at-age estimates despite the presence of age, growth and time-varying growth effects in the dataset. Very large errors in predicted size were produced by the Age-Effects model. The four other back-calculation models all provided slightly biased estimates of back-calculated size-at-age, with the Modified-Fry model providing the least biased estimates. Regardless of bias, both experimental and theoretical evidence indicated that back-calculated size was a better proxy of fish length than otoliths radius. Relationships between fish length and otoliths radius were allometric at the level of individuals, which explained why the Modified-Fry model performed better. However, this allometry was undetectable at the population level. This study represents the first attempt to validate modern back-calculation models using longitudinal data collected and analysed at the individual level. Our results suggest the use of the Modified-Fry model as a conservative approach in routine back-calculations of fish size at age from otoliths.

Aerial surveys have been used to estimate population abundance of both terrestrial and marine species; in the marine environment this has largely been used for air-breathing species that spend time regularly at the surface. Whale sharks spend a large proportion of their time close to the surface and so are amenable to aerial survey techniques. This study presents the results of six years of synoptic aerial belt-surveys done nearly daily during the peak whale shark season around the island of Mahe, Seychelles. A total of 580 survey flights were flown providing 699.7 hours of survey record. A seasonal peak of shark sightings per hour was recorded in September or October in most years with the maximum on a single survey of 28.4 h- 1 in October 2006. The aerial survey data were used to generate an estimate of relative population abundance indicating that highest mean annual relative population estimate was also in 2006, with an estimate of 38, while the lowest mean estimate was 11 in 2004. These estimates were then compared to weekly capture-mark-recapture estimates of abundance based on unique individual identification data. The results indicate that the use of aerial survey data alone may give an acceptable indication of instantaneous relative population abundance but further refinement is necessary to estimate absolute regional abundance.

Over-exploitation of whale sharks threatens the future of these wide-ranging pelagic fish. A long-term continuous record (4436 sightings) from a large aggregation (300–500 resident individuals) of whale sharks at Ningaloo Reef, Western Australia shows that mean shark length declined linearly by nearly 2.0 m and relative abundance measured from ecotourism sightings (corrected for variation in search effort and environmental stochasticity) has fallen by approximately 40% over the last decade. This population-level result confirms previous predictions of population decline based on projection models parameterised using mark-recapture estimates of survival. The majority of these changes are driven by reductions in the number of large individuals in the population. Phenomenological time series models support a deterministic (extrinsic) decline in large females, although there was some evidence for density dependence in large males. These reductions have occurred despite the total protection of whale sharks in Australian waters. As this species is highly migratory, the rapid change in population composition over a decade (

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.

This study recorded the scarring rate and severity for whale sharks Rhincodon typus from three Indian Ocean aggregations (Australia, Seychelles and Mozambique), and examined whether scarring (mostly attributed to boat strikes and predator attacks) influences apparent survival rates using photo-identification libraries. Identifications were based on spot-and-stripe patterns that are unique to individual whale sharks. Scarring was most prevalent in the Seychelles aggregation (67% of individuals). Predator bites were the most frequent source of scarring (aside from minor nicks and abrasions) and 27% of individuals had scars consistent with predator attacks. A similar proportion of whale sharks had blunt trauma, laceration and amputation scars, the majority of which appeared to be caused by ship collisions. Predator bites were more common (44% of individuals) and scars from ship collisions were less common at Ningaloo Reef than at the other two locations (probability of among-site differences occurring randomly = 0·0007 based on a randomized multinomial contingency analysis). In all aggregations, scars occurred most often on the caudal fin, which may result from the fin being the body part closest to the surface when boats pass over, or they may provide a large target for predator attack. No evidence was found for an effect of scarring on apparent survival (φ; mean ±s.e.) for the Ningaloo (not scarred φ= 0·858 ± 0·033; scarred φ= 0·929 ± 0·033) or Seychelles populations (not scarred φ= 0·502 ± 0·060; scarred φ= 0·538 ± 0·070). The lower apparent survival of the Seychelles population may be attributed to a high number of transient whale sharks in this aggregation that might bias estimates. This study indicates that while scarring from natural predators and smaller vessels appears to be unrelated to whale shark survival, the effect of deaths related to ship strike need to be quantified to assist in future management of this species.

Jackson, G. D., Meekan, M. G., Wotherspoon, S., and Jackson, C. H. 2008. Distributions of young cephalopods in the tropical waters of Western Australia over two consecutive summers. – ICES Journal of Marine Science, 65: 140–147. Cephalopod paralarvae and juveniles were sampled with light traps deployed at the surface and deeper in the southern NW Shelf and on Ningaloo Reef off Western Australia during two consecutive summers. One cross shelf transect (Exmouth) was sampled in the late spring and summers of 1997/1998 (summer 1) and 1998/1999 (summer 2), and a second cross shelf transect (Thevenard) and a longshore transect (Ningaloo) along the Ningaloo Reef were sampled in summer 2. Species captured in the order of abundance were octopods, Photololigo sp., Sepioteuthis lessoniana, and Sthenoteuthis oualaniensis. Most were captured in shallow traps except for Photololigo sp., which was common in both shallow and deep traps with larger animals found in deeper water. The presence of Idiosepius pygmaeus in deep water off Ningaloo Reef revealed the species to be eurytopic, inhabiting a wider range of habitats than previously known. Photololigo sp. and S. lessoniana were more abundant inshore, and octopods were especially abundant on mid-depth stations of the Exmouth transect, probably because of the turbulent mixing and increased productivity there. Fewer S. oualaniensis were caught during the first summer on the Ningaloo transect (n = 5) than during the second summer (n = 79).

Pop-up satellite archival tags (PSATs) are now widely used to document the geographic and vertical movements of large pelagic fishes. These instruments record measurements of ambient light, depth and temperature at regular intervals and the light data are used to compute daily estimates of latitude and longitude. Several methods have been developed to improve those estimates, including the application of Kalman filter models and matching sea surface temperatures (SST) from tags with remotely sensed SSTs. Despite their widespread use, few studies have evaluated the accuracy of raw estimates of location from PSATs or quantified the improvements that may result from refinement techniques. To assess the accuracy of raw and refined estimates of locations from PSATs, we attached two PSATs and one Argos satellite-linked transmitter (SAT tag) to one whale shark (Rhincodon typus) at Ningaloo Reef, Western Australia. The root mean square error (RMSE) in raw estimates of location provided by the PSATs was 5.16� latitude and 2.00� longitude. Estimates were more accurate after processing the data with a Kalman filter (RMSE = 2.97� latitude and 0.78� longitude) and most accurate after processing with a Kalman filter model that integrates SST measurements (RMSE = 1.84� latitude and 0.78� longitude). We also assessed the precision of the PSAT-derived locations, and depth and temperature measurements by comparing the data from the two PSATs. Our findings support the use of archival tag data to reconstruct the large-scale movements of marine animals and demonstrate the significant improvements that may result from two refinement techniques.

Juvenile and adult reef fishes often undergo migration, ontogenic habitat shifts, and nocturnal foraging movements. The orientation cues used for these behaviours are largely unknown. In this study, the use of sound as an orientation cue guiding the nocturnal movements of adult and juvenile reef fishes at Lizard Island, Great Barrier Reef was examined. The first experiment compared the movements of fishes to small patch reefs where reef noise was broadcast, with those to silent reefs. No significant responses were found in the 79 adults that were collected, but the 166 juveniles collected showed an increased diversity each morning on the reefs with broadcast noise, and significantly greater numbers of juveniles from three taxa (Apogonidae, Gobiidae and Pinguipedidae) were collected from reefs with broadcast noise. The second experiment compared the movement of adult and juvenile fishes to reefs broadcasting high (>570 Hz), or low (

For organisms with complex life cycles, variation among individuals in traits associated with survival in one life-history stage can strongly affect the performance in subsequent stages with important repercussions on population dynamics. To identify which individual attributes are the most influential in determining patterns of survival in a cohort of reef fish, we compared the characteristics of Pomacentrus amboinensis surviving early juvenile stages on the reef with those of the cohort from which they originated. Individuals were collected at hatching, the end of the planktonic phase, and two, three, four, six and eight weeks post-settlement. Information stored in the otoliths of individual fish revealed strong carry-over effects of larval condition at hatching on juvenile survival, weeks after settlement (i.e. smaller-is-better). Among the traits examined, planktonic growth history was, by far, the most influential and long-lasting trait associated with juvenile persistence in reef habitats. However, otolith increments suggested that larval growth rate may not be maintained during early juvenile life, when selective mortality swiftly reverses its direction. These changes in selective pressure may mediate growth-mortality trade-offs between predation and starvation risks during early juvenile life. Ontogenetic changes in the shape of selectivity may be a mechanism maintaining phenotypic variation in growth rate and size within a population.

Selective mortality within a population, based on the phenotype of individuals, is the foundation of the theory of natural selection. We examined temperature-induced shifts in the relationships among early life history traits and survivorship over the embryonic and larval stages of a tropical damselfish, Pomacentrus amboinensis. Our experiments show that temperature determines the intensity of selective mortality, and that this changes with ontogeny. The size of energy stores determined survival through to hatching, after which egg size became a good indicator of fitness as predicted by theoretical models. Yet, the benefits associated with egg size were not uniform among test temperatures. Initial egg size positively influenced larval survival at control temperature (29 degrees C). However, this embryonic trait had no effect on post-hatching longevity of individuals reared at the higher (31 degrees C) and lower (25 degrees C) end of the temperature range. Overall, our findings indicate that the outcome of selective mortality is strongly dependent on the interaction between environment conditions and intrinsic developmental schedules.