The Francisco Estuary (SFE) is an important nursery habitat for leopard sharks (Triakis semifasciata), whose population has experienced an extreme decline in recent years. Previous studies have attributed the collapse of pelagic fish communities in the SFE to a change in nitrate/ammonium levels, as 38 wastewater treatment facilities discharge wastewater effluent into the SFE. This study aims to investigate whether these high levels of pollution are affecting leopard shark dietary and migratory behaviors. The team will also characterize the species’ life history diversity within California’s northern population by leveraging stable isotope analysis (SIA) and compound specific SIA of amino acids (CSIA-AA).
Stable isotope ecology follows the age old saying, “you are what you eat.” When animals consume their prey, the chemistry (i.e., stable isotope composition) gets incorporated into the predator’s tissues. To study leopard shark ecology in the heavily human altered SFE, the team will use stable isotopes in tissue (e.g. teeth, vertebrae, and eye lenses) to track movement and trophic interactions over seasons and the development of young.
Bulk SIA and CSIA-AA of tissues will highlight inter- and intra-population differences in leopard shark diet and habitat preference, as well as how the sharks change based on those ecological preferences.