Overfishing decreases the population of trout living in a river. What would also decline because of the decreasing number of trout?
A mayflies that are part of the trout's diet
B. eels that compete with the trout for food
C. birds that use the trout as a source of food
D. fish that lay eggs that are eaten by the trout

C. birds that use the trout as a source of food

Explanation:

Living organisms feed on one another in their natural environment in order to obtain energy for their various activities. According to this question, overfishing by humans decreases the population of trout living in a particular river.

This means that in that aquatic ecosystem (river), the population of organisms that feed on trout as a source of energy will also decrease. In this case, it is the birds. Hence, birds that use the trout as a source of food.

producers: apple trees, potatoes, carrots, grains, acorns, cabbage, grass, corn, lettuce

consumers: deer, mice, rabbits, chickens, squirrels, horses, worms, cows

predators: eagles, frogs, wolves, owls

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.