Those fish species are removed/ weakened so the organisms that the fish eat have less natural predators and increase in population. They need to eat more kelp in order to sustain their population, resulting in a loss of kelp as there is suddenly more of a demand for it then the kelp can grow. All because the predators were removed from the food chain.
Reverse fault would be the answer
The answer is:
TO MAKE FOOD
I hope im right