Prey nutritional quality in a southern temperate estuary and hypersaline lagoon

Abstract Predator populations and food web dynamics are influenced by the nutritional quality of prey, not just prey availability. Temperate estuaries and lagoons are productive, dynamic environments, and evaluating prey nutritional quality is vital to understanding food webs in these ecosystems. This study tested whether the nutritional quality of macroinvertebrates and fishes in the Coorong—a large temperate estuary and lagoon system in southern Australia—differs between functional groups, seasons, regions, and size classes. Macroinvertebrates and fish were sampled seasonally throughout the ~ 100-km-long system and their energy content determined by bomb calorimetry, along with crude lipid and protein content. Fish had markedly greater energy content than macroinvertebrates. Within the macroinvertebrates, benthic decapods had the greatest energy content and annelids the lowest, while bentho-pelagic crustaceans, insect larvae, and molluscs had intermediate values. There was little evidence of spatial or temporal variation in energy content; however, variations in lipid and protein content were found. Nutritional quality of yelloweye mullet ( Aldrichetta forsteri ) also varied strongly with size. The nutritional content values are some of the first for coastal ecosystems in the southern hemisphere, which can inform bioenergetic and food web models, and further the understanding of trophic functioning in southern temperate estuaries.