Question

A dam is built on the Columbia River in 1938, and then eight more dams were built between 1940-1950. What happens to the fish populations when dams are built?

a. Fish populations increase due to improved habitat.
b. Fish populations remain unaffected.
c. Fish populations decline due to habitat disruption and barriers.
d. Fish populations thrive due to enhanced water quality.

Answer 1

The construction of dams leads to the decline of fish populations due to the alteration of natural habitats, disruption of migratory paths, and changes in water conditions.

Step-by-step explanation:

When dams are built, such as the ones on the Columbia River between 1938 and 1950, fish populations typically decline due to habitat disruption and barriers. Dams have a number of impacts that include obstructing migration routes for species like salmon, altered water temperatures, changes in water chemistry, flow characteristics, and sediment loads. These changes disrupt aquatic habitats and can have far-reaching effects on the ecology of the river both upstream and downstream. Fish ladders can help mitigate some of the effects on fish migration, but they do not fully solve the problems created by dams. Additionally, the operation of dams and the resulting reservoirs can flood areas, displacing both human and animal populations.