About This Project

How significant an impact do keystone shark species have on fisheries? We’re still in the dark because we don’t really know their diets. By using precise eDNA and fatty acids techniques, we will be able to determine sharks' diet and feeding behaviors. This will allow us a window into the true impact these top predators have on their ecosystem, assisting conservation efforts and laying the groundwork for using these new approaches to help us understand our oceans worldwide.

Ask the Scientists

What is the context of this research?

Shark diet knowledge is based on studies using limited geographic range and traditional approaches which involve dissecting and analyzing stomach contents. These techniques leave knowledge gaps because often stomachs are empty, and contents are partially digested beyond recognition. Prey present that is identifiable only represents recently consumed prey from their most recent location. How do you identify something that's been partially digested? Consumed prey leaves traces of DNA, which can be identified through eDNA down to the exact species. Fatty acids can be used to identify habitat influences on recent shifts in diet. Using Salmon sharks as our test species, these analyses will provide one of the first in-depth data sets to accurately determine sharks’ diet and impact on ecosystems.

What is the significance of this project?

This study will assist in the advancement of standard practices used in feeding ecology studies, creating methodology that can be built upon and further developed. Using the novel approach of eDNA and fatty acid analyses will supplement current data sets, leading to the much-needed enhancement of current conservation and management practices.

We are using Salmon shark as our study species because as an endothermic predator, they have an extensive range, migrating from subpolar to subtropical waters. Evidence of their movements suggest they primarily prey on a variety of salmon and other fish species. It has been estimated that their consumption rates are much higher than previously thought. This indicates Salmon shark predation on endangered salmon stocks may have significant impact.

What are the goals of the project?

The goal of this study is to use the novel methods of eDNA and fatty acid analysis to understand the diet of sharks. eDNA will provide insight into what they have recently eaten while fatty acids reflect their diet over the past weeks to months. Stomachs will be flushed with water and tissue present collected. eDNA from the water and tissue will be extracted. Water eDNA will be run through a PCR and tissue eDNA Sanger sequenced to provide accurate species identification. Lipids will be extracted from muscle and liver samples to build fatty acid profiles. The difference in muscle and liver profiles will indicate recent shifts in diet and habitat. These will be compared against known profiles of other top predators. We will evaluate the similarities to determine habitat and feeding ecology.