Use of Mesophotic Reefs By Invasive Western Atlantic Lionfish

The severe negative effects of invasive lionfish on western Atlantic shallow reefs are well documented, yet despite lionfish recorded on deeper reefs, the role of mesophotic reefs in invasive lionfish ecology and life history remains a significant gap in our knowledge. We combine unpublished and previously published studies of lionfish abundance and body length on shallow (0-30m) and mesophotic (30-150m) reefs from 63 sites in seven western Atlantic countries and eight sites in native-range Indo-Pacific countries. Lionfish were found at similar abundance on adjacent shallow and mesophotic reefs, while relative abundance distributions across the depth gradient were similar between invaded western Atlantic and native Indo-Pacific range sites. Mesophotic lionfish were often larger than shallow individuals, suggesting the mesophotic zone forms part of a natural ontogenetic migration, with older lionfish found at greater depths. Finding larger lionfish on MCEs raises crucial questions regarding whether these habitats act as a depth refuge, and could potentially be responsible for a disproportionately high number of local lionfish recruits. This study highlights the need for lionfish adaptive management to consider lionfish populations below the depth limit of recreational SCUBA diving, as the focus of most previous control (culling) measures has been shallow water.