TOEFL Integrated Writing Practice Test 001Wild Tuna

The numbers of wild tuna, large ocean-dwelling fish, have diminished due to excessive fishing. Recently, there have been attempts to cultivate tuna by raising them in ocean enclosures until they are mature enough for sale. However, this approach has faced several challenges and criticisms.

Firstly, captive female tuna are unable to produce eggs, so tuna farmers must capture substantial quantities of young wild tuna to stock their farms. This practice further depletes wild tuna populations. Since the farmed females cannot reproduce to replace the sold tuna, farmers are compelled to continually catch young wild tuna, which intensifies the decline in the wild population.

Secondly, the cost of raising tuna in farms is high because they require an expensive, high-protein diet made from other fish. Tuna consume almost exclusively small fish to get the necessary nutrients. Given that a single tuna can reach lengths of over four meters, weigh nearly 700 kilograms, and consume 70 kilograms of food each day, maintaining a tuna farm becomes economically challenging due to the high cost of feed.

Finally, tuna in ocean enclosures are prone to parasitic infestations. For example, tuna farms near southern Australia have struggled with blood flukes, parasites that infect the fish’s blood vessels and heart. These parasites weaken the tuna, slow their growth, and increase their vulnerability to other diseases, resulting in approximately 10 percent of the tuna dying before they can be sold.