Recently it has been observed that the population of salmon is decreasing in a large river. Environmentalists believe that it is happening because of the hydropower plant set up on that river. Which technology can prevent the salmon population from decreasing?

A.

drift nets

B.

noodling

C.

trapping

D.

fish ladders

The answer is letter D, fish ladders.

Explanation:

Fish Ladder - this is also known as a "fish pass" or "fish steps." It facilitates fish, such as salmon, to naturally migrate into their spawning ground.

Spawning - this is the process of releasing the eggs and sperms. When it comes to fishes, spawning is also known as a reproduction process. Salmons normally migrate from the ocean and swim to the upper reaches of the river to spawn.

In the situation above, the "hydropower plant" affects the spawning condition of the fish. Although the plant decreases the size and frequency of large flood events, it impairs the flushing capacity of the river, thereby affecting the spawning condition of the fishes. This causes the salmon population to decrease.

The fish ladder can prevent the salmon population from decreasing by providing a migration route for them. It will foster the spawning process as it will be easier for them to reach the spawning ground.