Sharks and Rays
Sharks, rays, skates, and sawfish (Elasmobranchs), are an extremely diverse group fish. Therefore, it is impossible to make blanket statements about their value. However, studies have shown that sharks keep other populations in check, remove weak or sick individuals, shift prey habitat, and balance ecosystems.
Sharks are also important for humans for food, tourism, and intrinsic value.
eOceans' research has engaged professional researchers and citizen scientists to document shark and ray populations – describing contemporary and historic baselines, identifying population 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)
Yellow stingray populations show decline throughout the Caribbean – cause is unknown
Note: The paper investigating inverted biomass pyramids, above, is often mis-cited. This is about scientific divers, and the fact that they count fish that enter their transect AFTER the survey starts, therefore inflating the density of mobile fish compared to that of stationary fish. Faster fish are more likely to enter the transect than stationary or slow fish, and therefore more bias of faster fish (top of the ecosystem).
We also contributed a chapter on the role of citizen science when conducting shark diving expeditions:
Responsible Shark and Ray Tourism: A guide to best practice
Our works has resulted in significant policy outcomes, including: