Friday, June 4, 2010

A Japanese Overfishing Crisis: From Bluefin Tuna to Sashimi

About the Bluefin Tuna

To describe the southern bluefin tuna, let's start with one word: HUGE. The southern bluefin tuna weighs approximately 440 pounds. Its body is extremely hydrodynamic and stiff, and its body temperature is warm, which allows the fish to swim at a very rapid speed.

The southern bluefin tuna is located in many parts of the world. It can be found in three major oceans: the Atlantic, Pacific, and Indian. The southern bluefin tuna can reproduce when it is at an age of 8 to 12 years. Due to overfishing, the southern bluefin tuna is listed as critically endangered.

The World Wildlife Fund expects the bluefin tuna population to be completely extinct by 2012.

What is the problem with the overfishing of the southern bluefin tuna? Why is this problem occurring? How is it occurring?

The reason the southern bluefin tuna is being overfished is because the fish has a lot of value. The southern bluefin tuna is used for sashimi, which is a Japanese food that consists of raw fish and sauce. The southern bluefin tuna's skin contains a lot of fat, which increases its value. In fact, just one of these fish can be worth $10,000 in the United States. High value, fatty skin, and a great ingredient in sashimi create a deadly combination that has led to the southern bluefin tuna being heavily overfished.

There are several ways in which the southern bluefin tuna is being overfished. For example, in Australia, the method of purse seine netting is used to catch these fish. In purse seine netting, a large net that is secured on the bottom scoops up many fish at once. Another method known as longline fishing is used to catch southern bluefin tuna in countries such as New Zealand, Japan, Indonesia, Korea, and Taiwan.

What are some ways in which this problem affects the environment, other organisms, and humans?

To get a good understanding of how overfishing of the bluefin tuna affects the environment, other organisms, and humans, we must first take a look at the food web to which the bluefin tuna belongs. The southern bluefin tuna is a part of the marine food web. This food web consists of over 300,000 marine species. The tuna is at the top of this massive food web. This food web begins with autotrophs. These are plants that use energy from the sun to create energy through the process of photosynthesis. The herbivores then receive energy by consuming the plants. Some examples of these herbivores are parrotfish, sea urchins, and manatees. The third trophic level of this food web consists of small carnivores such as snapper, mackerel, and other small fish. Then comes the tuna. The tuna sits at the top of the food web and feeds on smaller fish from the third trophic level. Sharks, which sometimes eat tuna, are also on this fourth trophic level, along with seals.

If the southern bluefin tuna becomes extinct because of overfishing, it will impact the environment, other organisms, and humans. First of all, it will alter the marine food web. Sharks that receive energy from tuna will have to find other organisms to eat. Also,small carnivores on the third trophic level of the marine food web might become overpopulated because there will be no tuna to feed on them. If these fish become overpopulated, they could potentially exceed their carrying capacity, which is the number of organisms that an environment can support indefinitely. If the carrying capacity of these small carnivores is exceeded, the species be on the verge of a collapse. There would simply be too much competition for food among these organisms.
The potential extinction of the southern bluefin tuna would also drastically affect humans. The sashimi market will be negatively impacted without one of its most prized ingredients. This could hurt the economy of many countries in Asia as well as the Oceania region. In addition, if the bluefin tuna becomes extinct, people all over the world would lack a nutritious source of protein that they once had before.

Obviously, the overfishing of southern bluefin tuna is completely due to biotic factors, which are factors caused by living organisms. Humans are the ones that are responsible for fishing the bluefin tuna beyond its limits and causing the species to become critically endangered. The need for southern bluefin tuna to keep the sashimi business running smoothly is the main biotic factors that is causing the bluefin tuna to be overfished.

The number of southern bluefin tuna has declined by 92 percent since the 1950s. Currently, it is critically endangered. The extinction of this amazing species of fish is not far away. If the World Wildlife Fund is predicting things correctly, then the southern bluefin tuna will be a thing of the past in just 2 years.


"Bluefin Tuna in Crisis." WWF - Bluefin Tuna in Crisis. WWF, n.d. Web. 8 Jun 2010. .

"Bluefin Tuna on The Edge of Extinction Due to Overfishing." Bluefin Tuna on the Edge of Extinction Due to Overfishing. Sincerely Sustainable, 9 Nov 2009. Web. 8 Jun 2010. .

Harding, Ben. "Overfishing to wipe out bluefin tuna in 3 years: WWF." Overfishing to wipe out bluefin tuna in 3 years: WWF. Reuters, 14 Apr 2009. Web. 8 Jun 2010. .

"Southern bluefin tuna." Southern bluefin tuna - Thunnus Maccoyii. Arkive, 2003-2010. Web. 8 Jun 2010. .

"Marine Food Chain." Marine Food Chain -- National Geographic. National Geographic, 2010. Web. 8 Jun 2010. .


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