The removal of sharks in our oceans will result in devastating consequences to the marine ecosystems. According to shark biologist, Dr. Erich Ritter, the killing of sharks is the “biggest ecological time bomb that we are facing” as sharks are the most abundant top predator on the planet, and thus have a strong influence in food web structures. Furthermore, Dr. Ritter believes that if we were to exterminate the world’s shark populations, we would destroy all food chains of the entire marine ecosystem.
ECOSIM Predictions
A study done by Stevens et al. (2000) used a mass balance model known as ECOSIM to predict the impacts of shark removals from ecosystems. The results of these studies demonstrated that decreases in shark populations could lead to strong and unforeseen variations in the abundances of several marine species, including species that are not the prey of sharks; this therefore indicates that shark depletion propagates down the entire food web in a very complex fashion. Conversely, some major prey species have actually decreased in population size with the removal of the sharks. The outcome of the ECOSIM study revealed the true complexity and unpredictability of the marine ecosystem.
Impacts on fisheries
The elimination of sharks, and thus the destruction of food webs, will not only be devastating to marine ecosystems, but to humans as well. As apex predators, sharks serve as keystone species and have a profound influence on all species of every subsequent trophic level. Therefore, eliminating even the smallest number of individuals of keystone species could result in a complete change of a food web. Consequently, alterations in food web processes could undermine the sustainability of not only sharks, but also worldwide fisheries.
According to the Food and Agriculture Organization (FAO) of the United Nations, fish are people’s most important single source of protein, providing approximately 16% of the world’s consumption of animal protein. Furthermore, it is estimated that around one billion people rely on fish as their primary protein source, particularly poorer and developing nations. In addition, fisheries have substantial social and economic importance, as at least 200 million people depend on the industry as a source of income. Clearly people depend on fisheries for survival. The eradication of sharks, however, will only propagate the already rapidly declining fisheries, which is projected to collapse completely by the year 2048.
Sharks even influence the very oxygen we breath!
In addition to the need of the oceans to provide food and economic security, humans are dependent on the ocean for oxygen. At the very bottom of all marine food webs are phytoplankton, photosynthetic marine microorganisms that-despite their extremely small size-provide over 70% of the world’s oxygen that we require to breathe. Furthermore, phytoplankton consume more carbon dioxide than anything else, and as a result, the oceans serve as the biggest carbon dioxide sink on the planet.
Dr. Ritter states, “if we kill them all [sharks], we destroy all food chains of an entire marine ecosystem and well, the majority of our oxygen comes from the ocean, so we should be more careful.” Conclusively, it is obvious that the mass slaughtering of 100’s of millions of sharks per year and thus destroying complex marine food webs may not be the smartest choice of action due to both the collapse of fisheries and risk of losing the oceans’ oxygen-giving photosynthetic microorganisms. Nevertheless, the overexploitation of sharks still continues at an increasing rate.
Conservation efforts must be set forth in order to protect these vital organisms before it is too late.
References
Kump, L., James K., and Robert C. (2010). The Earth System – Third Edition . (: Pearson Education, Inc.: Upper Saddle River, NJ).
Primack, R. (2008). A Primer of Conservation Biology . (Sinauer Associates, Inc.: Sunderland, MA).
Stevens, J. D., Bonfil, R., Dulvy, N. K., and Walker, P. A. (2000). The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems. ICES Journal of Marine Science . 57 , 476-494.
Stewart, R. (2007) Sharkwater . (Key Porter Books Limited: Toronto, Ontario).
Tidwell, J. and Allan, G. (2001). Fish as food: aquaculture’s contribution. EMBO Reports . 2 , 958-963.
Watts, S. (2003). Shark Finning . (WildAid and Co-Habitat).