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The author of the reading believes that tuna farming has faced several problems and criticisms.
The speaker in the listening, however, casts doubt on this claim by mentioning that promising solutions to address these problems have been discovered.
First of all, the author points out that due to female tuna’s incapability of producing eggs, tuna farmers catch large numbers of young wild tuna as an alternative, leading to a smaller population of wild tuna. This point is challenged by the speaker. He explains that because of a breakthrough, this situation can be changed. Scientists realized that they can get captive females to reproduce by injecting them with certain hormones. These injected hormones allow the females to lay eggs reliably without posing health risks to the tuna or to future consumers. Therefore, tuna farming can be feasible without further reduction in the number of wild tuna populations.
The author goes on to contend raising tuna on farms can be very expensive with the consideration of the high-protein food provided. The lecturer rebuts this argument. He suggests that the protein that tuna need could come from plants instead of fish. These high-protein plants can be processed to become an inexpensive food option while maintaining the ability to supply captive tuna with all the necessary protein and nutrients. Since the plants-derived food is inexpensive, the cost of tuna from tuna farms can be kept low.
Finally, the author states that the tuna confined to ocean cages are likely to become infested with blood flukes, parasites that can weaken their health. The lecturer, on the other hand, argues that effective steps can be taken to treat infestations by providing an example about the discovery made by some scientists studying a parasite problem in tuna farms in southern Australia. They found that when tuna cages were moved farther offshore into deeper waters, far fewer tuna have blood flukes in their bodies. It turns out that blood flukes need to stay close to shore to obtain required resources for their life cycle there. Once the tuna cages were moved into deeper waters where the blood flukes cannot thrive, blood fluke infestations among the caged tuna were basically stopped.