Answer:
Lack of shelter.
Explanation:
Although I cannot see the graph of the population over time, I am assuming it was exponentially rising and then began to decline. This is because the parrotfish were able to populate only until the species ran out of shelter. Once it ran out of shelter, the exposed fish began to die due to predators or the environment.
It may also be because of the drastic decline of living coral reefs. As coral reefs die, so do livable habitats for the parrotfish. As a result, the parrotfish decrease in population as fewer corals are available for the fish to live in.
