Body tissue of reef sharks similar to that of larger reef fishes, not sharks
Many of us have the impression that sharks have a large appetite. However, a new study proves otherwise, indicating that most coral reef sharks tend to consume bite-size prey that are smaller than a cheeseburger.
In a recent study, researchers from James Cook University's ARC Centre of Excellence for Coral Reef Studies examined the stomach contents of reef sharks to find out what their last meal was. In most cases, there was nothing inside the stomach.
"We were surprised to find a broad range of small prey items such as fish, molluscs, sea snakes, crabs and more often than not, nothing at all. These results suggest that reef sharks eat small meals infrequently and opportunistically," said lead author Dr Ashley Frisch.
The researchers then analysed the shark's body tissue, to further investigate the shark's dietary habits over a longer span of time.
"Although black-tip, white-tip and grey reef sharks have long been thought of as top predators, we found that the chemical structure of the sharks' body tissue actually matched closely with that of large reef fishes such as groupers, snappers and emperors. This result tells us that reef sharks and large fishes have a similar diet, but they don't eat each other. So rather than eating big fish, reef sharks are eating like big fish," said Dr Frisch.
For the researchers, it is important to understand how the food chain within the coral reef works, and to identify which species preys on which species. Using this information, they can understand the impact one species has on another species.
Co-author Dr Justin Rizzari concluded that the new findings has modified the current understanding of the food chains within the coral reef, adding that the larger, more conspicuous predators were not always the ones at the top of the food chain.
"We now know that reef sharks are an important link in the food chain, but they are not the last link in the food chain. In most cases, the top predators are tiger sharks, hammerhead sharks, or people," said Dr Rizzari.
Further Information: www.coralcoe.org.au
Link to the study: link.springer.com/article/10.1007/s00338-016-1415-2