Question

Imagine there is a species-specific fishing regulation that mandates that only adult fish of this species that are 75 cm or longer may be kept; shorter fish must be released. Based on your knowledge of natural selection, how would you predict that the average length of the adult fish population might be affected?

A) Length would remain unchanged.
B) Length would gradually increase.
C) Length would rapidly decrease.
D) Length would gradually decrease.
E) Length would rapidly increase.

Answer 1

The average length of the adult fish population might initially increase since smaller fish are given time to grow, but eventually, the population's average length may decrease due to the selective removal of the larger fish before they can reproduce. The correct option is B.

Step-by-step explanation:

Understanding the scenario where a fishing regulation mandates that only adult fish of a species 75 cm or longer may be kept, we can anticipate an effect on the population's average length due to selective pressure imposed by this rule.

As smaller, younger fish are more likely to be returned to the water to grow, over time, this could increase the proportion of genes that favor later maturation and larger size.

However, if this selective fishing continues, it could also lead to a decrease in the population's average size if the larger fish that reach the threshold for capture are removed before they reproduce.

The initial impact might be an increase in average size as smaller fish continue to grow, but ultimately, the selective removal of larger fish may lead to a gradual decrease in size, as the genetic composition shifts toward individuals that mature at smaller sizes. The correct option is b.