Question

which statement describes a variable that engineers can modify to increase the overall efficiency of fishways?
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a the volume of water trapped behind the dam
b the species of fish that approach the fishway entrance
c the volume of water required by individual fish in a holding pool
d the distance the fish need to swim to enter the fishway

Explanation:

To determine the variable engineers can modify for fishway efficiency, analyze each option:

• Option A: Water volume behind the dam is often fixed by the dam’s design and not easily modified for fishway efficiency.
• Option B: Fish species approaching the entrance are determined by the ecosystem, not something engineers can modify.
• Option C: Water volume required by individual fish in a holding pool is a biological requirement of the fish, not modifiable by engineers.
• Option D: The distance fish need to swim to enter the fishway is a design - related variable (e.g., adjusting the fishway’s entrance placement). Engineers can modify this distance to potentially increase fishway efficiency (e.g., reducing it to make it easier for fish to enter).

Answer:

D. the distance the fish need to swim to enter the fishway