Sharks, rays, skates and sawfish are fish, but differ in many ways to bony fish.
Together, they are called Elasmobranchs.
When considering the role of sharks, it is important to remember that they are extremely diverse.
Some can fit in the palm of your hand, like the Dwarf Lanternshark, while others like Whale Shark can reach the size of a bus. Some eat big mammals, like seals, and others eat microscopic zooplankton. Some have very small home ranges and move only a few kilometres, while others transit entire oceans.
Therefore, it is impossible to make blanket statements about their value. However, studies have shown that sharks:
- keep populations of smaller species in check
- remove weak or sick individuals
- shift prey habitat
- balance ecosystems
Sharks are also important for humans for food, tourism, and intrinsic value.
My own research has focused on shark and ray populations – describing contemporary baselines, identifing risks, and understanding conservation needs.
Findings have included:
- 103 million sharks die every year, which exceeds their reproductive potential
- sharks are largely absent in the Caribbean, and exponentially decrease with increased human population (no sharks with >100 people in 10km radius)
- Policy review of shark sanctuaries, what they are (and are not)
- Global description of manta ray populations, human uses and threats
- Recovery potential and conservation options of sharks
- Inverted biomass pyramids – sharks may not be as abundant on natural reefs as some studies suggest
- Sharks populations in Thailand – diversity, abundance, location, trends
- Yellow stingray population distribution, habitats – possible declines
- Juvenile shark habitats (nurseries) – showing microhabitat selection
- Economic value of sharks from fishing and tourism
- The Role of the Tourism Industry in Sharks: Conservation, Governance and Management
Note: The paper investigating inverted biomass pyramids, above, is my most mis-cited paper. It is not a recounting issue, but rather that mobile fish are more likely to enter a transect than stationary fish. Faster = more likely to enter and therefore more bias of faster fish (top of the ecosystem). If you want to discuss this, please contact me.
I led the citizen science section of:
- Responsible Shark and Ray Tourism: A guide to best practice
Policy outcomes resulting from the above work includes:
- manta rays being listed by CITES for international trade protections
- sharks being listed by CITES for international trade protections
- Bahamas Shark Sanctuary