Communal or competitive? Stable isotope analysis provides evidence of resource partitioning within a communal shark nursery

Quantifying the diet of sympatric co-occurring predatory species is a challenging task, made more so when investigations attempt to focus on specific age groups. This is the task that confronts efforts to understand dietary resource partitioning among co-occurring juvenile shark species within nursery areas. Here, stable isotope analysis (delta C-13 and delta N-15) is used to overcome these challenges in describing species dietary resource partitioning strategies within the communal shark nursery area of Cleveland Bay, Queensland, Australia. We analyzed the isotopic composition of 3 distinct tissues, (muscle, blood plasma, and red blood cells), for 7 species of shark and 3 species of large predatory teleost to investigate whether these communal areas support their diverse array of predators without the need for resource partitioning strategies. Clustered delta N-15 values for all examined species indicated feeding within the same trophic level; however, wide ranging delta C-13 values denoted exploitation of several primary carbon sources. Our results demonstrate inter-species resource partitioning strategies at work within the examined communal shark nursery, altering the previous interpretation of these areas as resource-rich and/or competitionlimited environments.