ORIGINAL PAPER Lionfish in the eastern Pacific: a cellular automaton approach to assessing invasion risk Matthew W. Johnston • Sam J. Purkis Received: 29 August 2013 / Accepted: 7 April 2014 / Published online: 13 April 2014 Ó Springer International Publishing Switzerland 2014 Abstract The lionfish invasion in the Atlantic and Caribbean has proceeded with vigor since their introduction in the 1980s or early 1990s. Lionfish affect recruitment of juvenile fish to reefs due to predation and are found in densities far surpassing that of their native Indo-Pacific. There is concern that the lionfish may become introduced and proliferate (through aquarium releases, transport on floating debris, or passage through the Panama Canal in ship ballast water) in the eastern tropical and north Pacific. This study presents the first known prediction of the potential for establishment of lionfish in the eastern Pacific Ocean. Through computational modeling, we compare and contrast the dynamics of random hypo- thetical introductions of lionfish into the eastern Pacific and Atlantic Oceans in order to highlight the different potentials for invasion in both basins. Connectivity between discrete regions (precincts) in both the Atlantic and eastern Pacific are examined and settlement densities are calculated to indicate possible locations of establishment of breeding lionfish popu- lations. Our results suggest that lionfish, which are successful invaders in the Atlantic, may not be as successful in the eastern Pacific due to weak meso- scale connectivity which reduces the rapid spread of lionfish larvae. Keywords Connectivity  Lionfish  Pacific Ocean  Atlantic Ocean  Computer modeling  Invasive species Introduction The invasive lionfish (Pterois volitans/miles complex) has spread rapidly throughout the Atlantic, Caribbean, and Gulf of Mexico since its introduction to Florida waters in the late 1980s to early 1990s (Whitfield et al. 2002; Freshwater et al. 2009; Schofield 2010). Albins and Hixon (2011) deem lionfish to be the most successful and potentially destructive marine invasion in the Atlantic region to date. There is concern that lionfish may be introduced to, and rapidly colonize, the eastern tropical and north Pacific region of North and Central America (Williams et al. 2012). For brevity, going forward these two regions will be referred to simply as the ‘Atlantic’ and ‘eastern Pacific’. Importantly, the question of whether or not the eastern Pacific conveys comparable risk factors to the Atlantic for a successful invasion has not been addressed to date. To prevent a widespread incursion of lionfish, such as that witnessed in the Atlantic, data M. W. Johnston (&)  S. J. Purkis National Coral Reef Institute, Nova Southeastern University Oceanographic Center, 8000 North Ocean Drive, Dania Beach, FL 33004, USA e-mail: johnmatt@nova.edu S. J. Purkis e-mail: purkis@nova.edu 123 Biol Invasions (2014) 16:2681–2695 DOI 10.1007/s10530-014-0696-z