This was an observational field study conducted from June - August 2012 to determine whether lionfish behavior and movements change at different local lionfish and prey fish densities. The study was conducted on sixteen reefs in Rock Sound, Elethera, The Bahamas. All reefs were at least 300 m from any reef on which lionfish removals had occurred, and were selected to encompass a range of natural lionfish densities and reef sizes.

A pair of divers visited each reef at three times of day: within 2 hours of sunrise (‘dawn’), greater than 3 hours from sunrise or sunset (‘midday’), and within 2 hours of sunset (‘dusk’). Upon arriving at a reef, observers counted the number of lionfish present by conducting lionfish-focused searches. For each lionfish, observers recorded the size (total length, visually estimated to the nearest cm), behavior, and location the moment it was sighted. Behaviors were categorized as resting (sitting on the substrate, not moving), hovering (in the water column oriented parallel to the bottom, but not moving), swimming (actively moving), or hunting (oriented head down with pectoral fins flared). Location was categorized as the microhabitat on which lionfish were observed (e.g. under a ledge, on top of the reef, in the surrounding seagrass) and later divided into two major categories: sheltering (hidden under structure) or exposed (on top of reef or in surrounding area). Then, 10-minute focal observations were conducted on two randomly-selected lionfish or a single lionfish when there was only one individual present per reef. During focal observations, a trained observer recorded the behavior of lionfish at 30-second intervals for 10 minutes using the same categories as above. The observers also noted any strikes at prey, successful kills, and obviously aggressive interactions (chases, posturing) between lionfish or between lionfish and other species. Throughout the entire visit to each reef, divers noted the time when any lionfish departed from or arrived at the reef and its behavior. A lionfish was defined as departing from the reef if it traveled at least 10 m from the reef. A lionfish was considered arriving at a reef if it swam in from the surrounding areas and had not been previously observed at that reef during that observation period. At the conclusion of the focal observations, the divers re-counted the number of lionfish present while conducting a survey of resident native fishes. Divers recorded the abundance and body size (TL) of all fish 1 - 15 cm TL, native mesopredators that are ecologically similar to lionfish (e.g. Cephalopholis cruentata [graysby grouper]), and top predators (e.g. Epinephelus striatus [Nassau grouper]) on and within 1 m of the reef.