Resource partitioning in gurnard species using trophic analyses: the importance of temporal resolution

Dietary habits and intra- and inter-specific trophic ecology of co-occurring <i>Lepidotrigla mulhalli</i> and <i>L. vanessa</i> from south-eastern Australia were analysed using stomach content and stable isotope ratios (δ¹³C and δ¹⁵ N). Both species are bottom-feeding carnivores that consumed mainly benthic crustaceans, but teleosts were also abundant in the diet of larger <i>L. vanessa</i>. Non-metric multidimensional scaling (nMDS) ordination and analysis of similarity (ANOSIM) of dietary data revealed significant inter-specific dietary differences; i.e. food resource partitioning. Carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope values were similar between <i>L. mulhalli</i> and <i>L. vanessa</i>, however, suggesting similar trophic positioning. Ontogenetic changes in diet composition and stable isotope values were evident. As <i>L. vanessa</i> grew, they preyed upon larger individuals, such as teleosts and caridean shrmips, but no such trend was observed in the diets of<i> L. mulhalli</i>. Adults of both species were significantly enriched in ¹⁵N relative to juvenile conspecifics thus supporting these data. Consequently, in this study, both methodologies, i.e. stomach content and stable isotope analyses, provided evidence of inter- and/or intra-specific dietary segregations and trophic niche partitioning between co-occurring <i>L. mulhalli</i> and <i>L. vanessa</i> off Tasmanian waters.