Question

overfishing occurs when more fish are removed from an ecosystem than can be maintained by the population. overfishing can lead to significant population declines in economically important species. the passage describes additional impacts of overfishing on populations.
according to the passage, which mechanism explains the observed changes in fish size over time?
a. smaller fish produce fewer eggs than larger fish do, so they contribute fewer offspring to the next generation.
b. the average size of pink salmon returning to spawn decreased from 6.0 pounds to approximately 4.5 pounds.
c. fish that are small enough to escape fishing nets are more likely to survive than larger fish.
d. scientists found that atlantic silversides exhibited changes in feeding and foraging rates after four generations of selection.

Explanation:

To determine the mechanism explaining fish size changes due to overfishing, we analyze each option:

• Option A: Discusses offspring production, not survival related to fishing nets (unrelated to overfishing's impact on size via selection).
• Option B: Only states a size change, not the mechanism.
• Option C: Overfishing removes larger fish (caught in nets), so smaller fish (that escape) survive and reproduce, leading to smaller average size over time. This explains the mechanism.
• Option D: Discusses feeding changes, not size change due to overfishing.

Answer:

C. Fish that are small enough to escape fishing nets are more likely to survive than larger fish.