Plectropomus Leopardus Research Articles

GROW OUT CULTURE OF CORAL TROUT Plectropomu leopardus IN FLOATING NET CAGES WITH DIFFERENT FEEDING FREQUENCIES

<em><span>A study on the effect of feeding frequency on coral trout culture <span style="text-decoration: underline;">Plectropomus</span> <span style="text-decoration: underline;">leopardus</span> was conducted in floating net cages. The aim of this study was to determine an optimum feeding frequency for better growth rate and feed conversion ratio. The experiment was divided into two stages, i.e.; using fish with a range of body weight of 24 to 100 g (1<sup>st</sup> stage), and fish with a range of 100 to150 g (2<sup>nd</sup> stage). The first stage, consisted of four treatments of feeding frequencies, i.e. four times </span><span lang="IN">a </span><span>day (4/1), three times a day (3/1), twice a day (2/1), and once a day (1/1). For the second stage experiment, the treatments applied were, three times a day (3/1), twice a day (2/1), once a day (1/1), and once in two days (1/2). Each treatment was in triplicate. At each feeding time, experimental fish were fed with dry pellets to apparent satiation. Both first and second experimental stages showed that the treatments of twice a day (2/1) feeding frequency attained significantly higher growth rates and lower feed conversion ratios than other treatments (P<0</span><span lang="IN">.</span><span>05). Survival rate at the first stage (4/1), three times a day (3/1), twice a day (2/1), higher than (1/1) (P<0</span><span lang="IN">.</span><span>05). But in the second stage the survival rate is not significant. The most optimum feeding frequencies for this species is 2/1 for the fish of 24 to 150 g BW.</span></em>

The distribution and abundance of reef-associated predatory fishes on the Great Barrier Reef

Predatory fishes are important components of coral-reef ecosystems of the Great Barrier Reef (GBR) through both the ecological functions they perform and their high value to recreational and commercial fisheries, estimated at $30 million in 2014. However, management of GBR predatory fish populations is hampered by a lack of knowledge of their distribution and abundance, aside from that of the highly targeted coral trout (Plectropomus spp. and Variola spp.). Furthermore, there is little information on how these fishes respond to environmental stressors such as coral bleaching, outbreaks of coral-feeding starfishes (Acanthaster planci) and storms, which limits adaptive management of their populations as the frequency or severity of such natural disturbances increases under climate change. Here, we document the distribution and abundance of 48 species of reef-associated predatory fishes and assess their vulnerability to a range of natural disturbances. There were clear differences in predatory fish assemblages across the continental shelf, but many species were widespread, with few species restricted to either inshore or offshore waters. There was weak latitudinal structure with only a few species restricted to either the northern or southern GBR. On the whole, predatory fishes were surprisingly resistant to the effects of disturbance, with few clear changes in abundance or species richness following 66 documented disturbances of varying magnitudes.

The Use of Carotene Materials as the Source of Red Color Pigmentation on Leopard Grouper Larvae (Plectropomus leopardus)

Carotenoid is one of nutrition factors which can improve red color pigmentation. The purpose of this study was to investigate the best type of carotene which can increase red pigment performance and to evaluate how long the effect should be retaining in order to maintain red color performance on leopard grouper seeds. This study consisted of 2 experiments; those were the effect of various kinds of carotene materials in feed addition and the effect of the termination of the addition of carotene materials in the feed toward red color performance on leopard grouper seed. The treatments given to the first experiment were the provision of various kinds of carotene materials which were type of A. Haematococcus pluvialis , B. Phaffiarhodozyma , C. Astax Oil, D. Control (without carotene materials) and the treatments to the second experiment are A. Leopard grouper seed – phaffia was still given additional Phaffia rodhozyma , B. Leopard grouper seed – haematococcus was still given additional Haematococcus pluvialis , C. leopard grouper seed (from larvae - phaffia / haematoco ccus ) was terminated from carotene materials addition. The first experiment was applied from larva up to D60 seed and for the second experiment was the follow-up response from the first experiment conducted on D60 seed up to D150. Based on the study result, it indicates that carotene materials of Haematococcus pluvialis type gave the best color performance improvement (P value 4.71 x 10 -7 < 0.05). The provision of carotene materials intake decreases color performance both visually and total contain of carotene (P value 5.97 x 10 -5 < 0.05) (Tabel 1). Carotenenoids should be continuously given as trigger to maintain red color performance on leopard grouper seed. There was protein band in the range of 82.1 – 84.2 kDa which was assumed as protein expression of astaxanthin

Potential Enhanced Survivorship of Crown of Thorns Starfish Larvae due to Near-Annual Nutrient Enrichment during Secondary Outbreaks on the Central Mid-Shelf of the Great Barrier Reef, Australia

The Great Barrier Reef (GBR) is currently experiencing widespread crown of thorns starfish (CoTS) outbreaks, as part of the fourth wave of outbreaks since 1962. It is believed that these outbreaks have become more frequent on the GBR and elsewhere in the Indo-Pacific and are associated with anthropogenic causes. The two widely accepted potential causes are (1) anthropogenic nutrient enrichment leading to the increased biomass of phytoplankton, the food of the planktonic stage of larval CoTS; and (2) the overfishing of predators in the juvenile to adult stages of CoTS, for example, commercially fished species such as coral trout. In this study, we show that the evidence for the nutrient enrichment causation hypothesis is strongly based on a large number of recent studies in the GBR. We also hypothesise that secondary outbreaks in the region between Cairns and Townsville can also be enhanced by nutrient enriched conditions associated with the annual nutrient discharge from Wet Tropics rivers.

Keas Perform Similarly to Chimpanzees and Elephants when Solving Collaborative Tasks.

Cooperation between individuals is one of the defining features of our species. While other animals, such as chimpanzees, elephants, coral trout and rooks also exhibit cooperative behaviours, it is not clear if they think about cooperation in the same way as humans do. In this study we presented the kea, a parrot endemic to New Zealand, with a series of tasks designed to assess cooperative cognition. We found that keas were capable of working together, even when they had to wait for their partner for up to 65 seconds. The keas also waited for a partner only when a partner was actually needed to gain food. This is the first demonstration that any non-human animal can wait for over a minute for a cooperative partner, and the first conclusive evidence that any bird species can successful track when a cooperative partner is required, and when not. The keas did not attend to whether their partner could actually access the apparatus themselves, which may have been due to issues with task demands, but one kea did show a clear preference for working together with other individuals, rather than alone. This preference has been shown to be present in humans but absent in chimpanzees. Together these results provide the first evidence that a bird species can perform at a similar level to chimpanzees and elephants across a range of collaborative tasks. This raises the possibility that aspects of the cooperative cognition seen in the primate lineage have evolved convergently in birds.

Trophic niche and spatio-temporal changes in the feeding ecology of two sympatric species of coral trout (Plectropomus leopardus and P. laevis)

This research was conducted under research permits from the Great Barrier Reef Marine Park Authority (G12/35236.1 and G14/36624.1) and Queensland Department of Primary Industries and Fisheries (144482). This project was funded by the Australian Government's National Environmental Research Program (Tropical Ecosystems Hub Project 6.1). M.R.H. was supported by an Australian Research Council Future Fellowship (#FT100101004). Additional funding was granted to J.K.M. from the James Cook University College of Marine and Environmental Sciences and the Graduate Research School; an Australian Coral Reef Society (ACRS) Award and a Natural Sciences and Engineering Research Council (NSERC) PGS D scholarship. All research was conducted under JCU Animal Ethics Permit A1933. Laboratory analysis was assisted by A. Hussey and K. Johnson. The authors thank crew from the R/V 'James Kirby', F. de Faria, S. Moore, P. Yates, M. Espinoza, and E. Ledee.

Rising temperatures may drive fishing-induced selection of low-performance phenotypes

Climate warming is likely to interact with other stressors to challenge the physiological capacities and survival of phenotypes within populations. This may be especially true for the billions of fishes per year that undergo vigorous exercise prior to escaping or being intentionally released from fishing gear. Using adult coral grouper (Plectropomus leopardus), an important fisheries species throughout the Indo-Pacific, we show that population-level survival following vigorous exercise is increasingly compromised as temperatures increase from current-day levels (100–67% survival at 24–30 °C) to those projected for the end of the century (42% survival at 33 °C). Intriguingly, we demonstrate that high-performance individuals take longer to recover to a resting metabolic state and subsequently have lower survival in warm water compared with conspecifics that exercise less vigorously. Moreover, we show that post-exercise mortality of high-performance phenotypes manifests after 3–13 d at the current summer maximum (30 °C), while mortality at 33 °C occurs within 1.8–14.9 h. We propose that wild populations in a warming climate may become skewed towards low-performance phenotypes with ramifications for predator-prey interactions and community dynamics. Our findings highlight the susceptibility of phenotypic diversity to fishing activities and demonstrate a mechanism that may contribute to fishing-induced evolution in the face of ongoing climate change.

Carotenoids of Red, Brown, and Black Specimens of Plectropomus leopardus, the Coral Trout (Suziara in Japanese).

This study investigated the carotenoids occurring in the integument of Plectropomus leopardus, the coral trout. For a red specimen, the major carotenoids included astaxanthin diester and monoester, as well as α-cryptoxanthin ester, tunaxanthin diester, adonixanthin diester, adonirubin ester, and adonirubin; for brown and black specimens, tunaxanthin diester was the main carotenoid. 1H-NMR and MS spectral analyses showed that docosahexaenoic acid was the sole fatty acid esterified with xanthophylls in the coral trout.

Effect of the creation of a marine protected area on populations of Coral Trout in the coral triangle region

Reef fish respond differently to reserve protection. The abundance and biomass of sedentary species and those with limited mobility should be higher inside the marine reserve and decline with increased distance from the center of the reserve. Reserve protection reduces fishing mortality and allows recovery or maintains fish population abundance within the reserve. We assessed the effects of protection on reef fish, including three species of Coral Trout (Plectropomus spp.), and hard coral cover at a marine reserve surrounding Lankayan Island, Sabah Malaysia, after 11 years of a ‘no-take’ policy. Underwater visual census conducted at 8 closed sites and 4 open sites indicated that total reef fish biomass and abundance, and Plectropomus spp. biomass were significantly higher inside the reserve. Eleven years of no-take policy appears to maintain Plectropomus spp. biomass up to 5 km from the reserve center. Hard coral cover influenced reef fish abundance and biomass but it did not affect the presence of Plectropomus spp. Our findings suggest that the effectiveness of a no-take marine reserve not only requires consideration of ecological connectivity, reserve size and location, but also socio-economic factors including compliance, enforcement availability and community participation to achieve greater benefits.

Effects of climate change on coral grouper (Plectropomus spp.) and possible adaptation options

Global climate change is increasingly considered one of the major threats to tropical coastal fisheries, potentially undermining important revenue and food security provided by coral reef ecosystems. While there has been significant and increasing work on understanding specific effects of climate change on coral reef fishes, few studies have considered large-bodied fisheries target species, limiting understanding of the effects of climate change on tropical fisheries. This review focuses on coral grouper (Plectropomus spp., and mainly Plectropomus leopardus), which are heavily fished throughout the Indian and Pacific oceans, and represent an exemplar group to assess potential effects of climate change on coral reef fisheries. In experimental studies, P. leopardus appear to be extremely sensitive to increasing ocean temperature, exhibiting declines in survivorship, aerobic scope and activity with relatively moderate increases in temperature. As such, ongoing ocean warming may jeopardize the catchability of coral grouper and sustainability of reef-based fisheries, especially at low latitudes. Notably, a significant portion of wild stocks of P. leopardus are already exposed to temperatures (≥30 °C) that have been shown to compromise individual performance and body condition. While there are considerable knowledge gaps in predicting effects of global climate change on coral grouper, such as their capacity to avoid, acclimate or adapt to changes in local environmental conditions, current information suggests that there is cause for concern. As such, we take the formative steps to outline both ecological and socioeconomic adaptations that could reduce vulnerability of coral reef fisheries to climate impacts on stocks of coral grouper, using a linked socio-economic framework.

Global warming may disproportionately affect larger adults in a predatory coral reef fish.

Global warming is expected to reduce body sizes of ectothermic animals. Although the underlying mechanisms of size reductions remain poorly understood, effects appear stronger at latitudinal extremes (poles and tropics) and in aquatic rather than terrestrial systems. To shed light on this phenomenon, we examined the size dependence of critical thermal maxima (CTmax) and aerobic metabolism in a commercially important tropical reef fish, the leopard coral grouper (Plectropomus leopardus) following acclimation to current-day (28.5°C) vs. projected end-of-century (33°C) summer temperatures for the northern Great Barrier Reef (GBR). CTmax declined from 38.3 to 37.5°C with increasing body mass in adult fish (0.45-2.82kg), indicating that larger individuals are more thermally sensitive than smaller conspecifics. This may be explained by a restricted capacity for large fish to increase mass-specific maximum metabolic rate (MMR) at 33°C compared with 28.5°C. Indeed, temperature influenced the relationship between metabolism and body mass (0.02-2.38kg), whereby the scaling exponent for MMR increased from 0.74±0.02 at 28.5°C to 0.79±0.01 at 33°C, and the corresponding exponents for standard metabolic rate (SMR) were 0.75±0.04 and 0.80±0.03. The increase in metabolic scaling exponents at higher temperatures suggests that energy budgets may be disproportionately impacted in larger fish and contribute to reduced maximum adult size. Such climate-induced reductions in body size would have important ramifications for fisheries productivity, but are also likely to have knock-on effects for trophodynamics and functioning of ecosystems.

Large-scale, multidirectional larval connectivity among coral reef fish populations in the Great Barrier Reef Marine Park.

Larval dispersal is the key process by which populations of most marine fishes and invertebrates are connected and replenished. Advances in larval tagging and genetics have enhanced our capacity to track larval dispersal, assess scales of population connectivity, and quantify larval exchange among no-take marine reserves and fished areas. Recent studies have found that reserves can be a significant source of recruits for populations up to 40km away, but the scale and direction of larval connectivity across larger seascapes remain unknown. Here, we apply genetic parentage analysis to investigate larval dispersal patterns for two exploited coral reef groupers (Plectropomus maculatus and Plectropomus leopardus) within and among three clusters of reefs separated by 60-220km within the Great Barrier Reef Marine Park, Australia. A total of 69 juvenile P.maculatus and 17 juvenile P.leopardus (representing 6% and 9% of the total juveniles sampled, respectively) were genetically assigned to parent individuals on reefs within the study area. We identified both short-distance larval dispersal within regions (200m to 50km) and long-distance, multidirectional dispersal of up to ~250km among regions. Dispersal strength declined significantly with distance, with best-fit dispersal kernels estimating median dispersal distances of ~110km for P.maculatus and ~190km for P.leopardus. Larval exchange among reefs demonstrates that established reserves form a highly connected network and contribute larvae for the replenishment of fished reefs at multiple spatial scales. Our findings highlight the potential for long-distance dispersal in an important group of reef fishes, and provide further evidence that effectively protected reserves can yield recruitment and sustainability benefits for exploited fish populations.

Contrasting patterns of vertical and horizontal space use of two exploited and sympatric coral reef fish

Understanding spatial distribution and temporal variation in movement patterns of closely related species is relevant for deciphering how resources are selected and whether interactions between species affect resource use patterns. The horizontal space use and vertical space use of two exploited reef fish, Plectropomus leopardus and P. laevis (all adults), were compared at mid-shelf Helix Reef and Lodestone Reef in the Great Barrier Reef over ~3 years using passive acoustic telemetry. Both species were detected throughout the 12-month duration of transmitters (mean detection period: ~270 days) and often made deep movements to ~40 m possibly related to reproductive behaviour (spawning). Differences in space use were apparent between species, with P. laevis consistently using greater area around reefs throughout the year. Overall, depth use patterns were similar between species; however, when daily detections were grouped in 2-h periods, P. laevis remained shallower and had greater variation in depth use compared to P. leopardus. Contrasting patterns of space use between these co-occurring species, in conjunction with known dietary dissimilarities, indicate distinct habitat use and resource preferences that are important for conservation and fisheries management.

Measuring niche overlap between co-occurring Plectropomus spp. using acoustic telemetry and stable isotopes

Investigating niche overlap in exploited fish species can reveal behavioural information necessary to improve conservation and fisheries management at a species level. The present study examined spatial and dietary overlap between two co-occurring reef fish, namely Plectropomus leopardus and P. maculatus, at an inshore reef in the Great Barrier Reef Marine Park using acoustic telemetry and stable isotopes. Movements of tagged fish within an acoustic array of 19 receivers deployed along a narrow reef portion of Orpheus Island were monitored for up to 3 years. Although space use was similar between species, spatial overlap was rare and P. maculatus (n=30) was consistently deeper than P. leopardus (n=32). Dietary overlap between species was high based on overlapping δ15N and δ13C isotopic niches in muscle tissue (n=20). The complementary stable isotope and acoustic telemetry data revealed these species had similar isotopic niches but distinct space use patterns, which may be a product of competition for resources. These findings show species-specific behaviours within a genus commonly managed or reported as a single entity, and provide new information on partitioning of resources by Plectropomus spp. in inshore reef environments.

Molecular changes in skin pigmented lesions of the coral trout Plectropomus leopardus

A high prevalence of skin pigmented lesions of 15% was recently reported in coral trout Plectropomus leopardus, a commercially important marine fish, inhabiting the Great Barrier Reef. Herein, fish were sampled at two offshore sites, characterised by high and low lesion prevalence. A transcriptomic approach using the suppressive subtractive hybridisation (SSH) method was used to analyse the differentially expressed genes between lesion and normal skin samples. Transcriptional changes of 14 genes were observed in lesion samples relative to normal skin samples. These targeted genes encoded for specific proteins which are involved in general cell function but also in different stages disrupted during the tumourigenesis process of other organisms, such as cell cycling, cell proliferation, skeletal organisation and cell migration. The results highlight transcripts that are associated with the lesion occurrence, contributing to a better understanding of the molecular aetiology of this coral trout skin disease.

Synergistic Effects of Marine Reserves and Harvest Controls on the Abundance and Catch Dynamics of a Coral Reef Fishery

Marine no-take reserves, where fishing and other extractive activities are prohibited, have well-established conservation benefits [1], yet their impacts onfisheries remains contentious [2-4]. For fishery species, reserves are often implemented alongside more conventional harvest strategies, including catch and size limits [2, 5]. However, catch and fish abundances observed post-intervention are often attributed to reserves, without explicitly estimating the potential contribution of concurrent management interventions [2, 3, 6-9]. Here we test a metapopulation model against observed fishery [10] and population [11] data for an important coral reef fishery (coral trout; Plectropomus spp.) in Australia's Great Barrier Reef Marine Park (GBRMP) to evaluate how the combined increase in reserve area [12] and reduction in fishing effort [13, 14] in 2004 influenced changes in fish stocks and the commercial fishery. We found that declines in catch, increases in catch rates, and increases in biomass since 2004 were substantially attributable to the integration of direct effort controls with the rezoning, rather than the rezoning alone. The combined management approach was estimated to have been more productive for fish and fisheries than if the rezoning had occurred alone and comparable to what would have been obtained with effort controls alone. Sensitivity analyses indicate that the direct effort controls prevented initial decreases in catch per unit effort that would have otherwise occurred with the rezoning. Our findings demonstrate that by concurrently restructuring the fishery, the conservation benefits of reserves were enhanced and the fishery cost of rezoning the reserve network was socialized, mitigating negative impacts on individual fishers.

Protected areas preserve natural behaviour of a targeted fish species on coral reefs

Marine protected areas are increasingly being implemented to attain a variety of conservation and fisheries management objectives. Although rarely considered, protection of targeted species within these areas may also conserve behaviours (e.g. boldness) that are often the first removed by human exploitation. Here we examine fish behaviour in fished, no-take, and no-entry management zones for a highly targeted reef fish species (coral trout; Plectropomus leopardus) on coral reefs in two regions of the Great Barrier Reef Marine Park, Australia. Using three behavioural metrics (flight-initiation distance, pre-flight behaviour, and escape trajectories), we demonstrate how protected areas, particularly no-entry zones, can effectively conserve naïve or bold behavioural traits in fish populations. Flight-initiation distance was consistently highest in fished zones, but the effects of protection afforded by no-take and no-entry zones varied by study region. Flight-initiation distance was consistently higher for fish above the minimum legal retention size limit, except in no-entry zones of the southern region. This indicates that no-entry zones may be maintaining near-natural, pre-exploitation behaviour, which could have considerable implications for the genetic and social structures of a highly valuable commercial species. Conservation and fisheries management would therefore benefit from an increased understanding of how fish behaviour can influence population structures, and how these populations may be influenced by fishing and other human interactions.

Top predators negate the effect of mesopredators on prey physiology.

Summary Predation theory and empirical evidence suggest that top predators benefit the survival of resource prey through the suppression of mesopredators. However, whether such behavioural suppression can also affect the physiology of resource prey has yet to be examined.Using a three‐tier reef fish food web and intermittent‐flow respirometry, our study examined changes in the metabolic rate of resource prey exposed to combinations of mesopredator and top predator cues.Under experimental conditions, the mesopredator (dottyback, Pseudochromis fuscus) continuously foraged and attacked resource prey (juveniles of the damselfish Pomacentrus amboinensis) triggering an increase in prey O2 uptake by 38 ± 12·9% (mean ± SE). The visual stimulus of a top predator (coral trout, Plectropomus leopardus) restricted the foraging activity of the mesopredator, indirectly allowing resource prey to minimize stress and maintain routine O2 uptake. Although not as strong as the effect of the top predator, the sight of a large non‐predator species (thicklip wrasse, Hemigymnus melapterus) also reduced the impact of the mesopredator on prey metabolic rate.We conclude that lower trophic‐level species can benefit physiologically from the presence of top predators through the behavioural suppression that top predators impose on mesopredators. By minimizing the energy spent on mesopredator avoidance and the associated stress response to mesopredator attacks, prey may be able to invest more energy in foraging and growth, highlighting the importance of the indirect, non‐consumptive effects of top predators in marine food webs.

Fishery consequences of marine reserves: short-term pain for longer-term gain.

Marine reserves are often established in areas that support fisheries. Larval export from reserves is argued to help compensate for the loss of fishable habitat; however, previous modeling studies have focused on long-term equilibrium outcomes. We examined the transient consequences of reserve establishment for fished metapopulations, considering both a well-mixed larval pool and a spatially explicit model based on a coral trout (Plectropomus spp.) metapopulation. When fishing pressure was reallocated relative to the area protected, yields decreased initially, then recovered, and ultimately exceeded pre-reserve levels. However, recovery time was on the order of several years to decades. If fishing pressure intensified to maintain pre-reserve yields, reserves were sometimes unable to support the increased mortality and the metapopulation collapsed. This was more likely when reserves were small, or located peripherally within the metapopulation. Overall, reserves can achieve positive conservation and fishery benefits, but fisheries management complementary to reserve implementation is essential.

Key aspects of the biology, fisheries and management of Coral grouper

Coral grouper (genus Plectropomus), or coral trout, are members of the grouper family (Epinephelidae) and are one of the largest and most conspicuous predatory fishes on Indo-Pacific coral reefs. They are highly-prized food fishes that are targeted by subsistence, artisanal, commercial and recreational fisheries throughout their geographic range. Plectropomus have broadly similar diets and habitat requirements to other tropical groupers, but typically have faster growth and higher natural mortality rates. Although these characteristics are expected to increase population turnover and reduce innate vulnerability to environmental and anthropogenic impacts relative to other groupers, many Plectropomus populations are in decline due to the combined effects of overfishing and habitat degradation. In many locations, stock depletion from uncontrolled fishing, particularly at spawning aggregation sites, has resulted in local fishery collapse. Therefore, improved management of wild populations is urgently required to ensure conservation and sustainable fisheries of Plectropomus. Where possible, a combination of no-take marine reserves, market-based management approaches, and allocation or resurrection of property rights systems are recommended to complement conventional fishery management actions that limit catch and effort. Additional investment in aquaculture propagation is also needed to reduce fishing pressure on wild stocks and support management initiatives. This global synthesis of information pertaining to the biology, fisheries and management of Plectropomus will assist in guiding future management actions that are attempting to address a range of stressors including fishing, reef habitat degradation, and the escalating effects of climate change.