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 (δ¹³C and δ¹⁵N) 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 δ¹³C and δ¹⁵N values for P. leo pardus 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 δ¹⁵N 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.