1 3 Mar Biol (2015) 162:253–266 DOI 10.1007/s00227-014-2595-3 ORIGINAL PAPER Relationships of invasive lionfish with topographic complexity, groupers, and native prey fishes in Little Cayman Sonia Bejarano · Kathryn Lohr · Samantha Hamilton · Carrie Manfrino Received: 6 August 2014 / Accepted: 3 December 2014 / Published online: 24 December 2014 © Springer-Verlag Berlin Heidelberg 2014 lionfish density. Grouper biomass caused no clear reduction in mean lionfish density, but narrowed the variance. Lionfish invested more time hunting on rugose sites with a paucity of prey refugia, implying that these may be places where prey fish are most vulnerable to predation. Under the reasonable assumption that lionfish display strong site fidelity, targeted removals are likely to yield the highest conservation benefits if focused on most rugose sites and at the edges of drop-offs. Determining whether longer hunting times yield increased predation rates, and quantifying the effectiveness of physical refugia in protecting prey from lionfish predation strikes, are important future research directions. If topographic complex- ity determines lionfish hunting success, there is a scope for mapping the vulnerability of prey, thus optimising practises aimed at managing the invasion. Introduction Lionfish, conspicuously ornate carnivores native to Indo- Pacific coral reefs, were the first invasive marine species to become established in the Atlantic Coast of the USA and the Caribbean, after being introduced via a series of releases from aquariums. These were first documented off the coast of Florida in 1985 (Schofield 2010) and reached the insu- lar Caribbean by 2004 (Albins and Hixon 2008; Morris and Akins 2009; Green et al. 2011). To date, one species in particular, Pterois volitans, has spread throughout the East- ern and Southern Caribbean, including the Cayman Islands (Whitfield et al. 2002; González et al. 2009; Frazer et al. 2012). This rapid invasion has drastic direct and indirect impacts, which are particularly unwelcome in a region that has undergone a long history of ecological adversities (Gard- ner et al. 2003), and is poorly equipped with natural intrinsic counteracting mechanisms (McClanahan et al. 2002). Abstract The invasion of Indo-Pacific lionfish on Caribbean reefs has prompted resource-demanding removals. Ecological tools to optimise the outcome of these costly efforts are scarce. Topographic complexity usually correlates strongly with fish abundance and can be mapped over large spatial scales. Deter- mining the nature and strength of its relationship with lionfish abundance is therefore an important step in generating spatial prioritisation tools for removal programmes. Here, we quan- tify the relationships of lionfish density and hunting behaviour with topographic complexity, grouper biomass, and prey avail- ability on the north-east reefs of Little Cayman. Lionfish den- sity varied across sites irrespective of topographic complexity or density of prey fish, but was highest on the most rugose section of the reef terraces. Increased topographic complex- ity along the edge of the drop-offs caused modest increases in Communicated by D. Goulet. Electronic supplementary material The online version of this article (doi:10.1007/s00227-014-2595-3) contains supplementary material, which is available to authorized users. S. Bejarano (*) · K. Lohr · S. Hamilton Little Cayman Research Centre, Central Caribbean Marine Institute, North Coast Road, Little Cayman KY3 2501, Cayman Islands e-mail: sonia.bejarano@zmt-bremen.de S. Bejarano Leibniz Centre for Tropical Marine Ecology, Fahrenheitstraβe 6, Bremen 28359, Germany C. Manfrino School of Environmental and Sustainability Sciences, Kean University, 1000 Morris Ave, Union, NJ 07083, USA C. Manfrino Central Caribbean Marine Institute, P.O. Box 1461, Princeton, NJ 08540, USA