Behaviour of mesopredatory coral reef fishes in response to threats from sharks and humans.

Both sharks and humans present a potentially lethal threat to mesopredatory fishes in coral reef systems, with implications for both population dynamics and the role of mesopredatory fishes in reef ecosystems. This study quantifies the antipredator behaviours mesopredatory fishes exhibit towards the presence of large coral reef carnivores and compares these behavioural responses to those elicited by the presence of snorkelers. Here, we used snorkelers and animated life-size models of the blacktip reef shark (Carcharhinus melanopterus) to simulate potential predatory threats to mesopredatory reef fishes (lethrinids, lutjanids, haemulids and serranids). The responses of these reef fishes to the models and the snorkelers were compared to those generated by three non-threatening controls (life-size models of a green turtle [Chelonia mydas], a PVC-pipe [an object control] and a Perspex shape [a second object control]). A Remote Underwater Stereo-Video System (Stereo-RUV) recorded the approach of the different treatments and controls and allowed accurate measurement of Flight Initiation Distance (FID) and categorization of the type of flight response by fishes. We found that mesopredatory reef fishes had greater FIDs in response to the approach of threatening models (1402 ± 402-1533 ± 171 mm; mean ± SE) compared to the controls (706 ± 151-896 ± 8963 mm). There was no significant difference in FID of mesopredatory fishes between the shark model and the snorkeler, suggesting that these treatments provoked similar levels of predator avoidance behaviour. This has implications for researchers monitoring behaviour in situ or using underwater census as a technique to estimate the abundance of reef fishes. Our study suggests that, irrespective of the degree to which sharks actually consume these mesopredatory reef fishes, they still elicit a predictable and consistent antipredator response that has the potential to create risk effects.

Condition-dependent responses of fish to motorboats.

Anthropogenic noise is a pollutant of global concern that has been shown to have a wide range of detrimental effects on multiple taxa. However, most noise studies to-date consider only overall population means, ignoring the potential for intraspecific variation in responses. Here, we used field experiments on Australia's Great Barrier Reef to assess condition-dependent responses of blue-green damselfish (Chromis viridis) to real motorboats. Despite finding no effect of motorboats on a physiological measure (opercular beat rate; OBR), we found a condition-dependent effect on anti-predator behaviour. In ambient conditions, startle responses to a looming stimulus were equivalent for relatively poor- and good-condition fish, but when motorboats were passing, poorer-condition fish startled at significantly shorter distances to the looming stimulus than better-condition fish. This greater susceptibility to motorboats in poorer-condition fish may be the result of generally more elevated stress levels, as poorer-condition fish had a higher pre-testing OBR than those in better condition. Considering intraspecific variation in responses is important to avoid misrepresenting potential effects of anthropogenic noise and to ensure the best management and mitigation of this pervasive pollutant.

Coral degradation alters predator odour signatures and influences prey learning and survival.

Habitat degradation is a key factor leading to the global loss of biodiversity. This problem is particularly acute in coral reef ecosystems. We investigated whether recognition of predator odours by damselfish was influenced by coral degradation and whether these changes altered survival in the wild. We taught whitespot damselfish to recognize the odour of a predator in the presence of live/healthy coral or dead/degraded coral. Fish were tested for a response to predator odours in environments that matched their conditioning environment or in environments that were mismatched. Next, we taught blue damselfish to recognize the odour of three common reef predators in live and degraded coral environments and then stocked them onto live or degraded patch reefs, where we monitored their subsequent response to predator odour along with their survival. Damselfish learned to recognize predator odours in both coral environments, but the intensity of their antipredator response was much greater when the conditioning and test environments matched. Fish released on degraded coral had about 50% higher survival if they had been trained in the presence of degraded coral rather than live coral. Altering the intensity of antipredator responses could have rather profound consequences on population growth.

Boat noise affects the early life history of two damselfishes.

Anthropogenic noise can have a negative effect on the physiology and survival of marine fishes. Most research has focused on later life-stages, and few studies have investigated the effects of human-induced noise on embryogenesis. The current study investigated whether playback of motorboat noise affected the embryogenesis of the coral reef damselfishes, Amphiprion melanopus and Acanthochromis polyacanthus. Embryos reared under the playback of boat noise had faster heart rates compared to the ambient reef controls. The effects of noise on morphological development differed between species and the fundamental interrelationships between early life history characteristics changed dramatically under boat noise for Ac. polyacanthus. Noise treatments did not alter the survival rates of embryos under laboratory conditions. Although species specific, our findings suggest that anthropogenic noise causes physiological responses in fishes during embryogenesis and these changes have direct impacts on their development and these alterations may have carry-over effects to later life stages.

Impacts of increased ocean temperatures on a low-latitude coral reef fish - Processes related to oxygen uptake and delivery.

Increasing temperatures are expected to significantly affect the physiological performance of ectotherms, particularly in tropical locations. The shape of an organism's thermal reaction norm can provide important information on its capacity to persist under climate change scenarios; however, difficulty lies in choosing a measurable trait that best depicts physiological performance. This study investigated the effects of elevated temperatures on processes related to oxygen uptake and delivery, including oxygen consumption, haematology, and tissue health for a low-latitude population of coral reef damselfish. Acanthochromis polyacanthus were collected from the Torres Strait (10°31-46'S, 142°20-35'E) and maintained at current average ocean temperatures (+0 °C; seasonally cycling), + 1.5 °C and + 3 °C higher than present day temperatures for 10 months. Aerobic performance indicated a limit to metabolic function at + 3 °C (33 °C), following an increase in aerobic capacity at + 1.5 °C (31.5 °C). Neither haematological parameters nor gill morphology showed the same improvement in performance at + 1.5 °C. Gill histopathology provided the first indicator of a decline in organism health, which corresponded with mortality observations from previous research. Findings from this study suggest thermal specialisation in this low-latitude population as well as variation in thermal sensitivity, depending on the physiological trait.

Multiple predator effects on juvenile prey survival.

Predicting multiple predator effects (MPEs) on shared prey remains one of the biggest challenges in ecology. Empirical evidence indicates that interactions among predators can alter predation rates and modify any expected linear effects on prey survival. Knowledge on predator density, identity and life-history traits is expected to help predict the behavioral mechanisms that lead to non-linear changes in predation. Yet, few studies have rigorously examined the effects of predator-predator interactions on prey survival, particularly with marine vertebrate predators. Using an additive-substitutive design, we experimentally paired reef piscivores with different hunting mode [active predator, Pseudochromis fuscus (F); ambush predators, Cephalopholis boenak (B), Epinephelus maculatus (M)] to determine how behavioral interactions modified their combined impacts on damselfish prey. Results showed that behavioral patterns among predators matched those predicted from their hunting mode. However, it was the identity of the predators what determined the strength of any positive or negative interactions, and thus the nature and magnitude of MPEs on prey survival (i.e., risk-enhancing effects: treatments BB, MM and FM; risk-reducing: BM; and linear effects: FF, FB). Given the specificity of predator-predator interactions, none of the predators were fully functionally redundant. Even when two species seemed substitutable (i.e., predators F and M), they led to vastly diverse effects when paired with additional predator species (i.e., B). We concluded that knowledge of the identity of the predator species and the behavioral interactions among them is crucial to successfully predict MPEs in natural systems.

Multispecies spawning sites for fishes on a low-latitude coral reef: spatial and temporal patterns.

Spawning sites used by one or more species were located by intensively searching nearshore coral reefs of Kimbe Bay (New Britain, Papua New Guinea). Once identified, the spawning sites were surveyed repeatedly within fixed 5 m radius circular areas, for > 2000 h of observations ranging from before dawn to after dusk spanning 190 days between July 2001 and May 2004. A total of 38 spawning sites were identified on the seven study reefs distributed at an average of one site every 60 m of reef edge. Pelagic spawning was observed in 41 fish species from six families. On three intensively studied reefs, all 17 spawning sites identified were used by at least three species, with a maximum of 30 different species observed spawning at a single site. Spawning was observed during every month of the study, on all days of the lunar month, at all states of the tide and at most hours of the day studied. Nevertheless, the majority of species were observed spawning on proportionately more days from December to April, on more days around the new moon and in association with higher tides. The strongest temporal association, however, was with species-specific diel spawning times spanning < 3 h for most species. While dawn spawning, afternoon spawning and dusk spawning species were differentiated, the time of spawning for the striated surgeonfish Ctenochaetus striatus also differed significantly among sites. The large number of species spawning at the same restricted locations during predictable times suggests that these sites are extremely important on this low-latitude coral reef.

Social learning of predators in the dark: understanding the role of visual, chemical and mechanical information.

The ability of prey to observe and learn to recognize potential predators from the behaviour of nearby individuals can dramatically increase survival and, not surprisingly, is widespread across animal taxa. A range of sensory modalities are available for this learning, with visual and chemical cues being well-established modes of transmission in aquatic systems. The use of other sensory cues in mediating social learning in fishes, including mechano-sensory cues, remains unexplored. Here, we examine the role of different sensory cues in social learning of predator recognition, using juvenile damselfish (Amphiprion percula). Specifically, we show that a predator-naive observer can socially learn to recognize a novel predator when paired with a predator-experienced conspecific in total darkness. Furthermore, this study demonstrates that when threatened, individuals release chemical cues (known as disturbance cues) into the water. These cues induce an anti-predator response in nearby individuals; however, they do not facilitate learnt recognition of the predator. As such, another sensory modality, probably mechano-sensory in origin, is responsible for information transfer in the dark. This study highlights the diversity of sensory cues used by coral reef fishes in a social learning context.

Social learning improves survivorship at a life-history transition.

During settlement, one of the main threats faced by individuals relates to their ability to detect and avoid predators. Information on predator identities can be gained either through direct experience or from the observation and/or interaction with others, a process known as social learning. In this form of predator recognition, less experienced individuals learn from experienced members within the social group, without having to directly interact with a predator. In this study, we examined the role of social learning in predator recognition in relation to the survival benefits for the damselfish, Pomacentrus wardi, during their settlement transition. Specifically, our experiments aimed to determine if P. wardi are capable of transmitting the recognition of the odour of a predator, Pseudochromis fuscus, to conspecifics. The experiment also examined whether there was a difference in the rate of survival between individuals that directly learnt the predator odour and those which acquired the information through social learning compared to naïve individuals. Results show that naïve P. wardi are able to learn a predator's identity from experienced individuals via social learning. Furthermore, survival between individuals that directly learnt the predator's identity and those that learnt through social learning did not significantly differ, with fish from both treatments surviving at least five times better than controls. These results demonstrate that experience may play a vital role in determining the outcome of predator-prey interactions, highlighting that social learning improves the ability of prey to avoid and/or escape predation at a life-history transition.

Social learning and acquired recognition of a predator by a marine fish.

Predation is known to influence the distribution of behavioural traits among prey individuals, populations and communities over both evolutionary and ecological time scales. Prey have evolved mechanisms of rapidly learning the identity of predators. Chemical cues are often used by prey to assess predation risk especially in aquatic systems where visual cues are unreliable. Social learning is a method of threat assessment common among a variety of freshwater fish taxa, which incorporates chemosensory information. Learning predator identities through social learning is beneficial to naïve individuals as it eliminates the need for direct interaction with a potential threat. Although social learning is widespread throughout the animal kingdom, no research on the use of this mechanism exists for marine species. In this study, we examined the role of social learning in predator recognition for a tropical damselfish, Acanthochromis polyacanthus. This species was found to not only possess and respond to conspecific chemical alarm cues, but naïve individuals were able to learn a predators' identity from experienced individuals, the process of social learning. Fish that learned to associate risk with the olfactory cue of a predator responded with the same intensity as conspecifics that were exposed to a chemical alarm cue from a conspecific skin extract.

Stressed mothers - troubled offspring: a study of behavioural maternal effects in farmed Salmo salar.

Mature female Atlantic salmon Salmo salar were given intraperitoneal cortisol implants 1 week prior to stripping to examine the influence of simulated maternal stress on offspring boldness and social dominance. Behavioural tests originally designed to investigate stress responsiveness and coping styles in salmonids (i.e. feeding in isolation, dominance tests and acute confinement) were carried out on the offspring 1·5 years after hatching. In the feeding test, there were no differences between the two treatment groups in total feeding score or number of pellets eaten, but offspring from the cortisol-implanted females made more unsuccessful feeding attempts than offspring from control females. In dominance tests, there was no difference between controls and cortisol-treated fish regarding propensity to become socially dominant. A higher proportion of individuals with bite marks, however, was observed in the cortisol group when compared to controls. Cortisol-treated offspring that gained dominant rank in the dominance tests performed more aggressive acts after stable dominance-subordinate relationships were established compared to control winners. During acute confinement stress, offspring from cortisol-implanted females showed a reduction in the proportion of time they were moving compared to the controls. These results indicate that the maternal endocrine state at spawning affects several aspects of progeny behaviour potentially related to subsequent success and survival in farmed S. salar.

Crucial knowledge gaps in current understanding of climate change impacts on coral reef fishes.

Expert opinion was canvassed to identify crucial knowledge gaps in current understanding of climate change impacts on coral reef fishes. Scientists that had published three or more papers on the effects of climate and environmental factors on reef fishes were invited to submit five questions that, if addressed, would improve our understanding of climate change effects on coral reef fishes. Thirty-three scientists provided 155 questions, and 32 scientists scored these questions in terms of: (i) identifying a knowledge gap, (ii) achievability, (iii) applicability to a broad spectrum of species and reef habitats, and (iv) priority. Forty-two per cent of the questions related to habitat associations and community dynamics of fish, reflecting the established effects and immediate concern relating to climate-induced coral loss and habitat degradation. However, there were also questions on fish demographics, physiology, behaviour and management, all of which could be potentially affected by climate change. Irrespective of their individual expertise and background, scientists scored questions from different topics similarly, suggesting limited bias and recognition of a need for greater interdisciplinary and collaborative research. Presented here are the 53 highest-scoring unique questions. These questions should act as a guide for future research, providing a basis for better assessment and management of climate change impacts on coral reefs and associated fish communities.

Regulation of protogynous sex change by competition between corticosteroids and androgens: an experimental test using sandperch, Parapercis cylindrica.

Cortisol, the dominant corticosteroid in fish, and 11-ketotestosterone (11KT), the most potent androgen in fish, are both synthesized and (or) deactivated by the same two enzymes, 11beta-hydroxylase and 11beta-hydroxysteroid dehydrogenase. Cortisol is synthesized in response to stress (such as that caused by interaction with a dominant conspecific), whereas 11KT is synthesized during protogynous sex change. It has been hypothesized that corticosteroids (such as cortisol) inhibit 11KT synthesis via substrate competition, thereby providing a mechanism for the regulation of socially mediated, protogynous sex change. We tested this hypothesis by administering cortisol (50 microg g(-1) body weight) to female sandperch (Parapercis cylindrica) under social conditions that were permissive to sex change (i.e. in the absence of suppressive male dominance). Twenty-one days later, mean physiological cortisol concentration in cortisol-treated fish was 4.2-fold greater than that in 'socially stressed' female fish maintained in a semi-natural system. Although the dosage of cortisol was therefore considered to be favorable for engendering competitive inhibition of 11KT synthesis, all cortisol-treated fish changed sex, as did all sham-treated and control fish (n=7 fish per treatment). In addition, there was no effect of cortisol treatment on the rate of sex change or on the pattern of steroidogenesis. Thus, our results refute the hypothesis that protogynous sex change is regulated by substrate competition between corticosteroids and androgens.

Experimental test of the effect of maternal hormones on larval quality of a coral reef fish.

Maternal hormones can play an important role in the development of fish larvae. Levels of the stress hormone, cortisol, in females are elevated by social interactions and transferred directly to the yolk of eggs, where they may influence developmental rates. In some vertebrates, prenatal exposure to high levels of testosterone determine early growth rates, social status and reproductive success. The present study examined whether post-fertilization exposure of eggs of the tropical damselfish, Pomacentrus amboinensis (Pomacentridae), to natural levels of cortisol or testosterone directly affects larval morphology at hatching. Maternal and egg levels of cortisol and testosterone varied widely among clutches of eggs from local populations around Lizard Island on the Great Barrier Reef. The morphology of larvae produced by these local fish populations also varied widely and differed significantly among sites (e.g., standard length: 2.6-3.4 mm; yolk sac area: 0.01-0.13 × 10-2 mm2). Laboratory experiments showed that elevated cortisol levels in the egg reduced larval length at hatching, while slight elevations in testosterone increased yolk sac size. The influence of testosterone, and to a smaller extent cortisol, on larval morphology differed among egg clutches. These differences were partly explained by differences in initial egg hormone levels. Morphological changes induced by experimental hormonal regimes encompassed the entire range of variability in body attributes found in field populations. It is unclear whether cortisol influences growth alone or development rate or both. Testosterone appears to influence yolk utilization rates, and has no significant effect on growth, in contrast to its role in later developmental stages. Maternally derived cortisol and testosterone are important in regulating growth, development, and nutritive reserves of the embryo and larvae of this fish species. Factors that influence the maternal levels of cortisol and testosterone may have a major impact on larval mortality schedules and, therefore, on which breeding individuals contribute to the next generation.

Vancomycin-resistant enterococci in stool specimens submitted for Clostridium difficile cytotoxin assay.

The prevalence of, and clinical risk factors associated with, vancomycin-resistant enterococcal colonization were investigated in patients suspected of having Clostridium difficile infection. Stools submitted for C difficile cytotoxin testing were screened for vancomycin-resistant enterococci (VRE). Isolates were speciated and characterized further by antibiotic susceptibility testing, DNA fingerprinting, and DNA:DNA hybridization for detection of specific vancomycin resistance genes. Of the 79 evaluable patients identified during a 3-month period, 16.5% were VRE-positive. The VRE isolates were genetically heterogeneous, although all carried the vanA gene. DNA fingerprinting data suggest that patient-to-patient transmission occurred, implicating colonized patients as potential reservoirs for VRE transmission. A positive C difficile cytotoxin assay and diabetes mellitus were the only identifiable risk factors associated with VRE colonization. Patients at risk for C difficile infection therefore may serve as reservoirs for VRE.

Tuberculosis surveillance: lessons from a cluster of skin test conversions.

Mycobacterium tuberculosis has reemerged as a significant public health problem. Elderly persons, especially those in long-term care facilities, are among those at high risk for infection with M. tuberculosis. Frequently, their symptoms are not clearly indicative of M. tuberculosis, and the diagnosis may thus be missed. We discuss the investigation of a cluster of skin test conversions on one locked unit in our long-term care facility. During the epidemiologic investigation, four of 25 patients who had previously had negative results of purified protein derivative testing (16%) and eight of 95 employees (11%) had skin test conversions. Despite a comprehensive, costly evaluation, the index case was not found. We identified weaknesses in our employee and patient M. tuberculosis surveillance programs. Employee baseline purified protein derivative testing data were inadequate. Annual skin tests for employees with previously negative results were not mandatory. There was no mechanism in place to encourage compliance. We developed a plan to educate personnel about the reemergence of M. tuberculosis, signs and symptoms in elderly patients, and the placement and interpretation of purified protein derivative skin tests. Documentation of purified protein derivative surveillance of both patients and employees was computerized. The number of inpatient and outpatient negative-pressure rooms was increased. Appropriate personal protective equipment was made available for use in high-risk situations.

Strategies for the management and control of antibiotic resistant organisms on a spinal cord injury unit.

Individuals with a spinal cord injury (SCI) are at an increased risk of infection and colonization. Frequent lengthy hospitalizations, invasive procedures, and skin breakdown contribute to this risk. Intermittent antibiotic use influences the emergence of antibiotic resistance in these organisms. As a result, there is risk of transmission of these antibiotic resistant organisms (ARO). This article describes the application of a continuous quality improvement model to evaluate ARO management strategies in a SCI unit. A conservative, labor intensive, crisis management approach to the control of ARO was replaced with a more cost effective prospective plan. The new strategies were aimed at control rather than eradication and included collaborative, multidisciplinary planning and improved resource utilization. Efforts have been successful and have resulted in the control of ARO.