First Insights: How Juvenile Sevengill Sharks Use San Francisco Bay

After years of field sampling and analysing our muscle biopsies for stable isotope analysis, we can more confidently conclude that San Francisco Bay is a nursery area for sevengill sharks. Not only did we consistently encounter juveniles over years of sampling, but our stable isotope analysis demonstrated that juvenile sevengill baselines are from San Francisco Bay, indicating long-term residency for individuals. This means the Bay isn’t just a place where pups are born—it’s where they grow, develop, and learn to survive. Understanding this long-term use is key to shaping conservation strategies that protect them throughout their early life.

: Meghan releases a neonate broadnose sevengill shark back into San Francisco Bay after collecting samples. Photo © Madeline Marens

Our physiological data adds another layer to this story. Preliminary results suggest that stress levels in these juveniles vary based on factors like handling time and environmental conditions. Longer handling times correspond to increased physiological stress, reinforcing the need for quick, efficient catch-and-release practices to minimise harm. These findings are critical because they help us refine best practices that could reduce the negative impacts of fisheries interactions on young sevengill sharks.

By combining physiological stress assessments with stable isotope analysis, we’re building a more complete picture of how juveniles use San Francisco Bay and how human activities might influence their survival. Moving forward, we aim to translate these findings into actionable conservation strategies that protect this vital nursery ground, ensuring that sevengill pups can thrive in the Bay for years to come.

ID photo of a broadnose sevengill shark, that may be able to re-identify this animal in the future with it’s unique spot pattern. Photo © Meghan Holst