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

Abstract

ABSTRACT: 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 (δ13C and δ15N) 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 δ15N values for all examined species indicated feeding within the same trophic level; however, wide ranging δ13C 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 competition-limited environments.