Question

A river has different populations of lampreys and paddlefish. The paddlefish feed on zooplankton, while the lampreys feed on the paddlefish. Humans living around the river hunt the paddlefish. What will happen to the ecosystem if the paddlefish are hunted in excess?

Answer 1

A couple of things will happen. One, the paddlefish may be hunted into nonexistent numbers, meaning that that amount of zooplankton would increase. Two, due to the decreased amount of the paddlefish, the lampreys would moves elsewhere or begin to feed on something else. 

Answer 2

The answer is: The population of paddlefish will decrease, while the population of zooplankton will increase.

The paddlerfish is predator to zooplankton. An decrease in predator (in this example the paddlerfish) will increase the number and genetic variation in a population of zooplankton.

An decrease of food (in this example the paddlerfish) will decrease population of the lampreys.

Hman activity (hunting) decrease population of the paddlerfish.