Proceedings of the Gulf and Caribbean Fisheries Institute 66th Annual Conference 48 November 2013, Corpus Christi, TX, USA Page 1 All boom and no bust as the lionfish invasion progresses in Bacalar Chico Marine Reserve, Belize L'invasion des poissons lions s'agrandit sans fin dans le Réserve Marine Bacalar Chico, Belize La invasión del pez león crece sin cesar en la Reserva Marina Bacalar Chico, Belice JENNIFER K. CHAPMAN, CHARLOTTE L.A. GOUGH, JOANNA E. HUDSON, FRANCES K. HUMBER and ALASDAIR R. HARRIS Blue Ventures Conservation, Level 2 Annex, Omnibus Business Centre, 39-41 North Road, London N7 9DP, UK. KEYWORDS: LIONFISH, MANAGEMENT, STATUS / PEZ LEÓN, MANEJO, STATUS ABSTRACT The first confirmed sighting of invasive lionfish (Pterois volitans) in Belize was in 2008, and the species is now well established throughout the country. Lionfish sighting frequency in Bacalar Chico Marine Reserve, northern Belize, increased from 2011 to 2012, coupled with a significant upward shift in size class frequency distribution. Lionfish dissections confirmed that lionfish in Belize reproduce throughout the year, and a change in diet from fish- to shrimp-dominated was observed between years. A similar change in lionfish diet has been observed in Port Honduras Marine Reserve, southern Belize, and may be indicative of fish recruit depletion. Given that consistent removal of more than one third of the population is required to prevent population growth and expansion, market development is heralded as the most feasible management solution. As protected areas may provide a refuge for lionfish, an open-minded approach to developing alternative management solutions within protected areas must be applied. Recommended citation: Chapman, J., Gough, C.L., Hudson, J.E., Humber, F.K., and Harris, A.R. All boom and no bust as the lionfish invasion progresses in Bacalar Chico Marine Reserve, Belize. Proceedings of the Gulf and Caribbean Fisheries Institute 66th Annual Conference, 4-8 November 2013, Corpus Christi, Texas, USA. INTRODUCTION Invasive species have been highlighted as one of the greatest threats to global ecosystems (Mooney and Cleland, 2001; Wilcove et al., 1998); often leading to biodiversity loss, food web disruption and alterations in ecosystem structure (Jackson, 2008). The red lionfish, Pterois volitans, was introduced to the Atlantic in the 1980s (Morris and Whitfield, 2009). Its numerous venomous spines make it an unsavoury prey item, with few species recorded to successfully predate upon lionfish (Bernadsky and Goulet, 1991; Morris and Whitfield, 2009). This lack of predatory pressure, in combination with a generalist diet (Green et al., 2011; Green et al., 2012) and high annual fecundity in their non-native ranges (Morris and Whitfield, 2009), have enabled the establishment of rapidly growing populations of lionfish throughout the Caribbean (HRI, 2010; Ruttenberg et al., 2012; Schofield, 2009). The first lionfish officially recorded in Belize was at Turneffe Atoll in 2008 (Searle et al., 2012); the population expanded throughout the coastal waters of northern Belize in 2009 finally reaching Port Honduras Marine Reserve, in the far south of Belize, in 2010 (James Foley, TIDE, pers. comm.). Blue Ventures, observing an increase in opportunistic lionfish sighting frequency throughout 2010 during reef monitoring expeditions in Bacalar Chico Marine Reserve (BCMR), began systematically monitoring the lionfish invasion in August 2010. BCMR is one of seven marine protected areas (MPAs) that together form the Belize Barrier Reef Reserve System, a UNESCO World Heritage Site (UNESCO, 1996). Threats to reef health from coastal development, oil exploration, overfishing, climate change, and introduced species have led to its inclusion on the List of World Heritage Sites in Danger (UNESCO World Heritage Committee - Decision - 33 COM 7B.33). Located at the north of Ambergris Caye, BCMR borders the Mexican MPA, Arrecife de Xcalak. Covering 15,529 acres of coastal waters, BCMR encompasses coral reefs, seagrass beds, mangroves and lagoons.