ORCID Profile
0000-0002-7060-0023
Current Organisation
James Cook University
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Publisher: Wiley
Date: 03-09-2020
Publisher: Public Library of Science (PLoS)
Date: 28-06-2023
DOI: 10.1371/JOURNAL.PONE.0286570
Abstract: Mass coral bleaching events coupled with local stressors have caused regional-scale loss of corals on reefs globally. Following the loss of corals, the structural complexity of these habitats is often reduced. By providing shelter, obscuring visual information, or physically impeding predators, habitat complexity can influence predation risk and the perception of risk by prey. Yet little is known on how habitat complexity and risk assessment interact to influence predator-prey interactions. To better understand how prey’s perception of threats may shift in degraded ecosystems, we reared juvenile Pomacentrus chrysurus in environments of various habitat complexity levels and then exposed them to olfactory risk odours before simulating a predator strike. We found that the fast-start escape responses were enhanced when forewarned with olfactory cues of a predator and in environments of increasing complexity. However, no interaction between complexity and olfactory cues was observed in escape responses. To ascertain if the mechanisms used to modify these escape responses were facilitated through hormonal pathways, we conducted whole-body cortisol analysis. Cortisol concentrations interacted with habitat complexity and risk odours, such that P . chrysurus exhibited elevated cortisol levels when forewarned with predator odours, but only when complexity levels were low. Our study suggests that as complexity is lost, prey may more appropriately assess predation risk, likely as a result of receiving additional visual information. Prey’s ability to modify their responses depending on the environmental context suggests that they may be able to partly alleviate the risk of increased predator-prey interactions as structural complexity is reduced.
Publisher: The Royal Society
Date: 29-05-2019
Abstract: Habitat degradation is a key factor leading to the global loss of bio ersity. 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.
Publisher: Springer Science and Business Media LLC
Date: 31-10-2019
DOI: 10.1038/S41598-019-51798-2
Abstract: Coral reefs are degrading globally leading to a catastrophic loss of bio ersity. While shifts in the species composition of communities have been well documented associated with habitat change, the mechanisms that underlie change are often poorly understood. Our study experimentally examines the effects of coral degradation on the trait-mediated effects of predators on the morphology, behaviour and performance of a juvenile coral reef fish. Juvenile damselfish were exposed to predators or controls (omnivore or nothing) in seawater that had flowed over either live or dead-degraded coral over a 45d period. No interaction between water source and predator exposure was found. However, fish exposed to degraded water had larger false eyespots relative to the size of their true eyes, and were more active, both of which may lead to a survival advantage. Non-consumptive effects of predators on prey occurred regardless of water source and included longer and deeper bodies, large false eyespots that may distract predator strikes away from the vulnerable head region, and shorter latencies in their response to a simulated predator strike. Research underscores that phenotypic plasticity may assist fishes in coping with habitat degradation and promote greater resilience to habitat change than may otherwise be predicted.
Publisher: Wiley
Date: 25-03-2021
Abstract: A prerequisite for effective antipredator responses is the ability of a prey to distinguish animals that pose a threat from those that do not. Prey often have efficient learning mechanisms to learn threats but learning to recognize nonpredators may be equally or more important. Moreover, the ability to generalize learned information is of key importance for prey animals. Prey take information they know about one species to make ‘educated guesses’ about the predatory/nonpredatory status of other unknown species. Here, we investigate the ability of Whitetail damselfish Pomacentrus chrysurus to learn the identity of non‐predators and then generalize their responses to other unknown animals. Our work is completed within the context of unprecedented habitat degradation in reef ecosystems. When corals die, the remaining skeleton is colonized by algae, cyanobacteria and sessile invertebrates. These opportunistic colonists change the physical and chemical landscape of the reef and hence the background odour in which predator and non‐predator recognition occurs. Our results indicated that Whitetail damselfish learn to classify Moonwrasse Thalasomma lunare as a non‐predator through the process of latent inhibition, whereby the prey are repeatedly exposed to Moonwrasse odour multiple times in the absence of negative reinforcement. These fish subsequently generalized their nonpredator recognition to other unknown wrasse, but not distantly related fish. Of key importance was our finding that the patterns and extent of non‐predator learning and generalization were dramatically altered in dead coral habitats. As predicted, prey that learned the Moonwrasse as a nonpredator in live coral environments did not subsequently respond to Moonwrasse when we tried to teach them Moonwrasse was a predator in live coral. However, this non‐predator recognition was reduced in dead coral environments. Moreover, generalization completely failed when we changed from live to dead coral environments. Juvenile damselfishes need to rapidly catalogue the identity of unknown animals when they arrive at a reef. Changing background odours, that occur with changing tides and currents, means that prey need to learn non‐predator identities separately in each water source. This cognitive challenge likely has significant survival consequence in a changing environment. A free Plain Language Summary can be found within the Supporting Information of this article.
Publisher: Wiley
Date: 15-01-2018
Publisher: Springer Science and Business Media LLC
Date: 25-04-2019
DOI: 10.1038/S41598-019-43099-5
Abstract: Vessel noise represents a relatively recent but rapidly increasing form of pollution, which affects the many organisms that use sound to inform their behavioural decisions. Recent research shows that anthropogenic noise can lead to reduced responsiveness to risk and higher mortality. The current laboratory experiment determined whether the playback of noise from motorboats powered by two- or four-stroke outboard engines affected the kinematics of the fast-start response in a juvenile coral reef fish, and the time scale over which the effects may occur. Results show that the two engine types produce slightly different sound spectra, which influence fish differently. Playback of 2-stroke engines had the greatest effect on activity, but only for a brief period (45 s). While noise from 4-stroke outboard engines affected fast-start kinematics, they had half the impact of noise from 2-stroke engines. Two-stroke engine noise affected routine swimming more than 4-stroke engines, while 4-stroke noise had a greater effect on the speed at which fish responded to a startle. Evidence suggests that the source of the noise pollution will have a major influence on the way marine organisms will respond, and this gives managers an important tool whereby they may reduce the effects of noise pollution on protected communities.
Publisher: Elsevier BV
Date: 06-2019
Publisher: Oxford University Press (OUP)
Date: 2018
Publisher: The Royal Society
Date: 28-10-2020
Abstract: Coral reefs are degrading globally due to increased environmental stressors including warming and elevated levels of pollutants. These stressors affect not only habitat-forming organisms, such as corals, but they may also directly affect the organisms that inhabit these ecosystems. Here, we explore how the dual threat of habitat degradation and microplastic exposure may affect the behaviour and survival of coral reef fish in the field. Fish were caught prior to settlement and pulse-fed polystyrene microplastics six times over 4 days, then placed in the field on live or dead-degraded coral patches. Exposure to microplastics or dead coral led fish to be bolder, more active and stray further from shelter compared to control fish. Effect sizes indicated that plastic exposure had a greater effect on behaviour than degraded habitat, and we found no evidence of synergistic effects. This pattern was also displayed in their survival in the field. Our results highlight that attaining low concentrations of microplastic in the environment will be a useful management strategy, since minimizing microplastic intake by fishes may work concurrently with reef restoration strategies to enhance the resilience of coral reef populations.
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.MARPOLBUL.2019.02.054
Abstract: 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.
Publisher: Public Library of Science (PLoS)
Date: 23-07-2020
Publisher: The Company of Biologists
Date: 2020
DOI: 10.1242/JEB.230904
Abstract: Parasites can account for a substantial proportion of the biomass in marine communities. As such, parasites play a significant ecological role in ecosystem functioning via host interactions. Unlike macropredators, such as large piscivores, micropredators rarely cause direct mortality. Rather, micropredators impose an energetic tax, thus significantly affecting host physiology and behaviour via such sublethal effects. Recent research suggests that infection by gnathiid isopods (Crustacea) causes significant physiological stress and increased mortality rates. However, it is unclear whether infection causes changes in the behaviours that underpin escape responses or changes in routine activity levels. Moreover, it is poorly understood whether the cost of gnathiid infection manifests as an increase in cortisol. To investigate this, we examined the effect of experimental gnathiid infection on the swimming and escape performance of a newly settled coral reef fish and whether infection would lead to increased cortisol levels. We found that micropredation by a single gnathiid caused fast-start escape performance and swimming behaviour to significantly decrease and cortisol levels to double. Fast-start escape performance is an important predictor of recruit survival in the wild. As such, altered fitness related traits and short-term stress, perhaps especially during early life stages, may result in large scale changes in the number of fish that successfully recruit to adult populations.
No related grants have been discovered for Eric Fakan.