Why Sharks are Important to Ocean Ecosystems
Author: Hunter Wortmann
The oceans would not be the same without sharks. The plethora of species that exists would not be possible without our sharp-toothed friends. Why are sharks so important? Sharks maintain the balance of our ocean’s ecosystems. As a top predator, sharks are responsible for moderating all the animals who fall below them on the food web. They do this by consuming the weaker or not as well adapted individuals. In other words, only the stronger animals of the preyed upon species survive. This is not to say that sharks will continue hunting until all the members of one species are depleted, however sharks have had some impact on which species will thrive over the course history. Sharks are not eating all the time, they are opportunistic feeders which means they will eat when they can and for many species of shark, this is certainly not every day. There is a delicate balance in each ecosystem, and the decline of shark populations is tipping the scale.
Sharks have been the kings and queens of the ocean for a very long time. They have been on this planet for 450 million years and have a vast diversity of over 500 different species.
Maintaining healthy shark populations is key to the conservation of our oceans. Without sharks our ocean’s ecosystem would be overrun with organisms that do not provide proper sustenance or benefit local fish and marine mammal populations. Sharks are indirectly responsible for healthy coral reefs and seagrass habitats. For example, if the local tiger shark population gets too low, one of their prey items like the grouper become more abundant due to the lack of predators. The larger grouper population who naturally prey on herbivorous fish consume these smaller fish at a faster rate. With less of these algae-eating fish around more algae grows on and outcompetes the corals, (which are crucial to supporting a wide array of species). This trophic cascade occurs when a top predator like the tiger shark is removed from an ecosystem or is depleted to insignificant numbers. This event has far reaching effects not only on other fish and phytoplankton populations, it alters the efficiency of nutrient cycling.
The decline of shark populations doesn’t only affect other species in the ocean, it affects our economy as well. The lack of sharks present creates a trophic cascade which can affect populations of fish that humans eat as well, causing us to compete with our finned friends for limited resources. These types of alterations to an ecosystem are happening to many different fisheries around the world and causes multiple species to be at risk. The decline of sharks can also create a big problem for countries that rely on tourism to thrive: specifically ecotourism. One example is the country of Indonesia which is home to an abundance of different species of sharks. Indonesia supports dozens of shark hotspots all around its coasts and hosts hundreds of thousands of tourists each year who seek a combination of nature and adventure. In 2017, shark tourists contributed around 22 million dollars to the local economy.5 If the sharks’ numbers continue to decline, it is estimated that Indonesia will lose about a quarter of their earnings in the dive tour sector.5 An impact at this scale can be detrimental to a country’s economy and Indonesia is not the only country that is at risk.
For the health of the different ocean ecosystems as well as our economy, it is important for us to preserve sharks all around the world. It is imperative that we learn more about sharks and reflect on the impact we are having not only on the sharks, but on all the species in our oceans.
1. The Shark Handbook by Dr. Greg Skomal