Sharks, The Apex Predators

Sharks, the Apex Predators of the Sea

Behind all conservation, there is appreciation. The most important tool for successful conservation is knowledge, a clear understanding of why you care in the first place. Sharks are a vital species for a healthy ocean, however this fact is often forgotten for dramatic impact in media publications. Understanding why their existence is crucial for our ocean cuts out any clouded judgement upon sharks that may previously exist. 

Sharks are Apex Predators

Sharks are top or “apex” predators in the marine ecosystem. This is because they have very few natural predators. A cascade effect naturally occurs in a balanced, healthy ecosystem, whether it be marine or terrestrial. Sharks as the apex predator, act as a regulator for biodiversity (Friedrich, Jefferson & Glegg, 2014, 3). They directly limit the abundance of species below them in the cascade or food chain. Sharks diets are especially varied, so that no one species of prey will become low in numbers through over predation (Friedrich et al, 2014, 3). If certain populations of prey are low, sharks are able to switch to another food source. This continues throughout the food chain, and is a sign of a healthy, biodiverse ecosystem. It is a naturally occurring event, which is greatly important, to provide a balance of species within the ecosystem itself. 

An Ocean Without Sharks 

Studies have shown that the greater abundance of sharks, the greater the diversity of species (Paine, 1966, 65). When comparing two reefs, one with sharks and one without, the latter circumstance showed species absences. Without sharks, there is a risk of over predation by the middle to lower predatory species with evidence of over eating of vegetation or primary producers (kelp, phytoplankton, or sea grass). Herbivorous preying species are in abundance with increased competition on food sources, called a “Top-Down” effect (Martin, 2009, 111). This results in surplus of middle predatory species, and overeating of the lowest species on the food chain which ultimately effects the species richness, and biodiversity upon the reef. If this was to occur on a larger scale, it could be catastrophic. The health of the ocean would decline, and seriously affect the way we live. 

 Ocean Food Web Figure 1: Food web demonstrating sharks as the apex predator. Retrieved from Encyclopedia Britannica, Inc.

Ocean Food Web Figure 1: Food web demonstrating sharks as the apex predator. Retrieved from Encyclopedia Britannica, Inc.

Sharks have been on this planet for 450 million years, and are pretty amazing creatures. They come in many different types, from the gentle Whale shark (Rhincodon typus), to the notorious Great White (Carcharodon carcharias). Sharks are important for our ocean’s survival and need to be protected. There should be more concern of an ocean without sharks, rather than a beach with sightings and baited drum lines. As the apex predators of our largest ecosystem, sharks deserve our respect and our conservation efforts to protect them. 

Written by Jessica McCabe

 

 

Friedrich, L.A., Jefferson, R. & Glegg, G. (2014). Public Perceptions of Sharks: Gathering Support for Shark Conservation. Marine Policy, 47 :1-7. Doi: doi:10.1016/j.marpol.2014.02.003

Martin, R.A. (2009). Hunting Patterns and Geographic Profiling of White Shark Predation. Journal of Zoology, 279(2): 111-118. Doi: 10.1111/j.1469-7998.2009.00586.x 

Paine, R.T. (1966). Food Web Complexity and Species Diversity. The American Naturalist, 100 (910): 65-75. Retrieved from: http://oceana.org/sites/default/files/reports/Predators_as_Prey_FINAL_1.pdf

 

Image: Carnivore: Aquatic Food Web. (2011). [Art]. In Britannica Online for Kids. Retrieved from http://kids.britannica.com/comptons/art-55763