Overview

The environments occupied by sharks present what are called “stressors,” which can include stressful events (like capture), environmental stressors (like pollutants) and even perceived threats (like a loud noise that might not actually be dangerous but is still frightening). Animals respond to stressors physiologically, meaning the way their bodies function change to help them respond. SRC conducts research at the conservation-physiology nexus, working to understand stress in sharks and how it alters biological performance (acid-base balance, oxidative capacity), energy storage (triglycerides and other metabolites), pace of life (bio-logging), and reproduction (hormones). Data collected as part of this project are used to gain insights on shark vulnerability to fishing practices, how sharks manage the physiological costs of environmental stressors and different life stages.

Using a standardized fishing technique, we studied the sub-lethal (blood physiology) outcomes of fishing stress on coastal sharks. In one study, SRC researchers identified differences among species in whole blood lactate, partial pressure of carbon dioxide, and pH values. Lactate emerged as the sole measure affected by increasing hooking duration and shark size. This study also tagged animals to look at their post-release survival, and found that nearly 100% of all tracked tiger sharks reported for at least 4 weeks after release, which was significantly higher than bull (74.1%) and great hammerhead (53.6%) sharks.

In the paper (Gallagher et al. (2014)), members of the SRC team presented these results and discussed the physiological mechanisms that may lead to these differences.