Why is overfishing a problem?

When fish are removed from their habitats at a rate that exceeds their ability to reproduce, it's not surprising that the fish population is going to suffer. The same logic applies to almost all species; however, fish are delicious, nutritious and are enjoyed by people all across the world. Demand for fish as a food source is huge and is increasing along with the growing world population. From 1943 to 1997, the global consumption of fish increased from to 43 million metric tons to 91 million tons. In 2009, fishing rates hit 145 million tons, which provided 16% of the world's animal protein intake.

Just how much of an effect are we having on the fish population of our oceans? Here are the facts:

• 90% of larger, top predator fish species, such as tuna, swordfish and dolphin, have been taken out of our oceans
• 70% of the world's fisheries are either overexploited or crashed 
• According to The Organization for the Food and Agriculture of the United Nations (FAO), approximately 25% of fish captured worldwide are thrown overboard; these fish are usually caught unintentionally, or are of substandard quality or below the permitted size
• 95% of unintentionally caught fish that are thrown away are considered endangered or overexploited
• The FAO estimates that currently 80% of the 523 species of fish in our oceans are fully exploited, overexploited or extinct
• Only 25% of the total global fisheries are considered sustainable

The fact that a staggering 90% of top predators have been fished from our oceans is having tremendous consequences on ecosystem health. The removal of top predators within the ecosystem causes a shift as commercially valuable fish (bluefin tuna, cod, halibut) are replaced by smaller fish that feed on plankton. During this century, it is also possible that jellyfish will replace many of the fish species humans love to eat.

Nobody wants to eat jellyfish.

The facts go on and on. They clearly show that our vast, majestic oceans are not limitless after all. The resources they provide are exhaustible, and that is becoming clearer day by day. A 2006 global study suggests that if current overfishing rates continue, 100% of the world's fish stocks will collapse before the mid-century. Food supply will plummet severely, and ocean systems will not be able to recover from the reduced populations of marine species. 

A compelling question to ask is what is allowing overfishing to continue when all these decisively negative outcomes are occurring? My researched data strongly supports the idea that overfishing is caused by an increased demand for seafood, which ultimately forces fishermen to employ more effective devices to catch higher amounts of fish in shorter periods of time. Below is a flowchart I created outlining the constant cycle that leads to overfished conditions:

Figure 1: The overfishing cycle showing high demand by humans leads to less fish in our oceans!

References

1. By the Numbers: Oceans in Crisis. Babbit, Bruce James C. 2012. Environmental Defense Fund. 3 March 2011 <http://www.edf.org/oceans/numbers-oceans-crisis>. 
2. Jackson et al. "Historical overfishing and the recent collapse of coastal ecosystems." Science 293.5530 (2001): 629-637. Online. 
3. Jellyfish replace fish in over-exploited areas. Edwards, Lin. 16 Sept. 2011. PhysOrg. 3 March 2011 <http://www.physorg.com/news/2011-09-jellyfish-fish-over-exploited-areas.html>.
4. Overfishing: A Threat to Marine Biodiversity. Nuttall, Nick. 2004. UN. 3 March 2011 <http://www.un.org/events/tenstories/06/story.asp?storyID=800>.
5. Still Waters: The Global Fish Crisis. Montalgne, Fen. Feb. 2011. National Geographic: The Ocean. 3 March 2011 <http://ocean.nationalgeographic.com/ocean/global-fish-crisis-article/#page=1>.