Salmon farming threatens the health of wild salmon stocks primarily because:

• A. it increases the spread of diseases and parasites to wild populations
• B. it causes genetic modification of wild salmon
• C. it leads to overfishing of wild salmon for feed
• D. it reduces the oxygen content of rivers

Answer: (A)

Verified step by step guidance

1. Understand the context of salmon farming: Salmon farming involves raising salmon in controlled environments, such as aquaculture pens, to meet the demand for fish consumption.
2. Identify the primary concern: Salmon farming can negatively impact wild salmon populations through various mechanisms, including the spread of diseases and parasites, genetic modification, overfishing, and environmental changes.
3. Focus on disease and parasite spread: Farmed salmon are often kept in high-density conditions, which can lead to the proliferation of diseases and parasites. These pathogens can escape into the surrounding environment and infect wild salmon populations.
4. Evaluate other options: Genetic modification of wild salmon is less likely to occur directly from farming, and overfishing of wild salmon for feed is not a primary issue in salmon farming. Reduced oxygen content in rivers is more related to pollution or other environmental factors rather than salmon farming itself.
5. Conclude that the spread of diseases and parasites is the most significant threat posed by salmon farming to wild salmon stocks, as it directly impacts their health and survival.