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The Ecological Importance Of Sharks In The Perhentian Islands

The Ecological Importance of Sharks in the Perhentian Islands

2 mins read

Shark populations in many parts of the world’s oceans are declining at an alarming rate. This is mainly due to targeted capture, overexploitation of marine resources (both stock and reserves) and other anthropological activities.

The loss of sharks creates a cascading effect, which can lead to a decline in commercially important fish and shellfish species down the food chain. Moreover, key fish families that maintain the health of coral reefs such as tuna are also affected.

The role of sharks

Sharks usually prey on the sick and the weak members of their prey populations, and some also scavenge the seafloor to feed on dead carcasses. By removing the sick and the weak, they prevent the spread of disease and prevent outbreaks that could be devastating. Also, preying on the weakest individuals can strengthen the gene pools of the prey species.

Sharks as apex and mesopredators.
Sharks play a crucial role in maintaining a healthy ecosystems through their roles as apex and mesopredators. (Wikimedia Commons: CC-BY-SA 4.0 – Sharkcrew)

Sharks can also regulate the behaviour of their prey species through intimidation. For example, a study on tiger sharks in Australia found that green turtles concentrate and overgraze on the best seagrass patches in the absence of tiger sharks. However, when tiger sharks were present, turtles graze over a much broader area to avoid predation.

The importance of sharks in the Perhentian Islands

A declining shark population is obviously a global issue, but it could have especially large consequences on the Perhentian Islands. With a decline in the blacktip reef shark population, prey species can overgraze and if left unchecked, it can strain local resources. Consequently, this will affect other marine species and can also deplete the local fish population.

Blacktip reef sharks
Blacktip reef sharks around the Perhentian Islands exert a top-down control on the local coral reef ecosystem.

Loss of sharks would have an indirect, yet detrimental effect on the island’s economy which relies on tourism. Most tourists come to the islands to see sharks and other marine life on a snorkeling or diving trip. Furthermore, fish is a major food source for the local community, especially during the monsoon, so the impacts would be even more widespread.

Apart from the ecological importance of blacktip reef sharks, they are actually pretty cool as well. The pattern of their dorsal fin pigmentation is unique to the individual and can be used for their identification purposes. Hence, a simple, clear picture of this pigmentation is enough to differentiate between individuals. To be fair, it easier said than done as most sharks are good swimmers, but a bit of practice can lead to good results!

Check our PMRS page if you would like to help us with our shark ID scheme or improve your research diving skills.

By Ramona, Project Manager at the Perhentian Marine Research Station 2018

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