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Questions 16 to 17 refer to the passage below. For each question, select one answer choice, unless the instructions state otherwise.
The growth of aquaculture, or fish farming, may affect the levels of certain contaminants in consumable fish and shellfish. Dense colonies can increase stress and disease transmission among fish, in some cases requiring the administration of antibiotics. Studies have also found 5 higher levels of certain contaminants in farmed fish than in their wild counterparts, possibly due to differences in diet. For example, several studies have found higher concentrations of PCBs, organochlorine pesticides, and polybrominated diphenyl ethers (PBDEs) in farmed salmon.
Overharvesting also can affect the condition of fish and shellfish—not only the species being harvested, but also the species that prey on them—by disrupting the food web. Because of depleted food sources, predators can become more susceptible to disease (such as infection of rockfish by mycobacterial lesions). These infections are often confined to internal organs and may not be apparent to anglers, although in some cases they are associated with external sores as well. Some types of mycobacteria can also infect humans who handle diseased fish if the infection comes into contact with an open wound. The slow-developing infections are usually not severe in humans, but in some cases they can cause major health problems, especially in people with compromised immune systems.
Questions 16 to 17 refer to the passage below. For each question, select one answer choice, unless the instructions state otherwise.
The growth of aquaculture, or fish farming, may affect the levels of certain contaminants in consumable fish and shellfish. Dense colonies can increase stress and disease transmission among fish, in some cases requiring the administration of antibiotics. Studies have also found 5 higher levels of certain contaminants in farmed fish than in their wild counterparts, possibly due to differences in diet. For example, several studies have found higher concentrations of PCBs, organochlorine pesticides, and polybrominated diphenyl ethers (PBDEs) in farmed salmon.
Overharvesting also can affect the condition of fish and shellfish—not only the species being harvested, but also the species that prey on them—by disrupting the food web. Because of depleted food sources, predators can become more susceptible to disease (such as infection of rockfish by mycobacterial lesions). These infections are often confined to internal organs and may not be apparent to anglers, although in some cases they are associated with external sores as well. Some types of mycobacteria can also infect humans who handle diseased fish if the infection comes into contact with an open wound. The slow-developing infections are usually not severe in humans, but in some cases they can cause major health problems, especially in people with compromised immune systems.
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