What is the role in the environment of a lionfish?

This question is asking about the ecological niche of a lionfish. A niche can be defined as the role that an organism plays in its environment, and the lionfish (Pterois volitans) is a top level predator. As a top level predator, a big part of its niche is population control. Without apex predators present in an ecosystem, lower population numbers rapidly increase. They will eventually decline as food shortages arise and can't support the larger population. This famously happened in Yellowstone when the wolves were removed during the twentieth century. The lionfish is a slow-moving apex predator, so it may seem surprising that it is so high in the food web; however, they rely on their unusual coloration and fins to discourage potential predators. They capture prey by ambushing it and using their fan-like pectoral fins to slowly pursue and corner the prey. The lionfish is so good at occupying this particular niche that it has become an invasive species in many areas in recent years.
https://oceanservice.noaa.gov/education/stories/lionfish/lion04_biology.html

https://oceanservice.noaa.gov/facts/lionfish-facts.html