Depth and space use of leopard coralgrouper Plectropomus leopardus using passive acoustic tracking

Understanding fish movements can help define the seasonal importance of different habitats and isolate spatial and temporal vulnerability to exploitation. Leopard coralgrouper Plectropomus leopardus is one of the main targeted fishery species in the Great Barrier Reef; however, there is no information on long-term movement patterns based on continuous and frequent data points. The objective of this study was to determine long-term space use of P. leopardus and identify any seasonal variation in movement trends. A total of 124 P. leopardus were implanted with V13P acoustic transmitters between 2010 and 2012 and passively tracked. Forty-five VR2W receivers were deployed at 2 reefs to track the movements of tagged individuals. The influence of time of day, season, tagging year, location, and water temperature on several movement measures was investigated. Of the 124 fish tagged, 74 individuals had sufficient detections to be included in analysis of horizontal movement, and 55 were used to analyse vertical movements. Results showed increased horizontal movements and higher activity in deeper water during the day in the austral summer. Movement patterns, both vertically and horizontally, appeared to be influenced by water temperature, but also corresponded with spawning season. Despite increased movements during summer, individuals typically remained in a small area ~0.5 km2 throughout detection periods, indicating that long-range spawning-related movements are rare and that adequate resources are obtained within a small section of habitat year-round. This study provides long-term (~3 yr) movement data for an economically significant reef fish and increases knowledge of spatial and temporal space use patterns

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 similar to 3 years using passive acoustic telemetry. Both species were detected throughout the 12-month duration of transmitters (mean detection period: similar to 270 days) and often made deep movements to similar 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

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

Prey selection can influence interactions among species, the composition and abundance of prey, and ultimately the movement of energy within the ecosystem. Different species of the exploited coral trout Plectropomus spp. often co-occur in reef environments, but their foraging behaviour and ecological niches are largely unknown. To explore niche overlap and resource use of sympatric adult coral trout, stable isotopes (delta C-13 and delta N-15) were quantified for 3 tissues (muscle, red blood cells, and plasma) collected between August 2013 and February 2014 from P. leopardus (n = 117) and P. laevis (n = 36) at 4 reefs in eastern Australia. Bayesian standard ellipses were used to show that prey selection of P. leopardus varied considerably from P. laevis, particularly from P. laevis in the blue-spot colour phase. Size of adult individuals had little influence on d13C and d15N values for P. leopardus and both footballer and blue-spot colour phases of P. laevis. Spatiotemporal comparisons of P. leopardus trophic positions, made by adjusting baseline algae and planktonic d15N at each reef and sampling period, demonstrated that trophic positions varied in time and space, and warrants further investigation. This study highlights that sympatric species of coral trout have distinct ecological roles and will likely react differently to environmental disturbances and/or changes in habitat or prey composition

Stable isotope analysis reveals trophic diversity and partitioning in territorial damselfishes on a low-latitude coral reef

Investigating the niche overlap of ecologically similar species can reveal the mechanisms that drive spatial partitioning in high-diversity systems. Understanding how food resources are used and whether the diets of neighboring species are different are particularly important when considering the coexistence and functional role of species. Territorial damselfish on coral reefs are considered to be herbivores that defend algal mats from other food competitors. However, this guild contains numerous small species whose functional role and dietary diversification is poorly understood. Here, the relationships between diet and spatial distribution of seven intermediate-sized territorial damselfishes at Kimbe Bay, Papua New Guinea (5°30'S, 150°05'E) were investigated. These species partition habitat across three reef zones with distinct patterns of fine-scale distribution. It was predicted that neighboring species partition food resources with minimal dietary overlap. Examination of isotope ratios of carbon and nitrogen delineated three distinct feeding strategies: pelagic, reef-based, and an intermediate group feeding on both prey types. None of the species appear to be strict herbivores. Adjacent species exhibited high–intermediate trophic niche partitioning when examining pelagic versus reef-based production sources, with two species previously described as benthic herbivores exhibiting pelagic feeding. The study demonstrates that diet reinforces the patterns of spatial partitioning and coexistence among ecologically similar damselfishes. These findings add to a growing view that interspecific differences among similar species are lost when categorizing species into broad functional classifications, and that previous studies suggesting that territorial damselfish are strictly reef-based feeders may not be applicable in all systems or for all species