Environ Biol Fish DOI 10.1007/s10641-014-0236-9 Competitive interactions for shelter between invasive Pacific red lionfish and native Nassau grouper Wendel W.Raymond & Mark A. Albins & Timothy J. Pusack Received: 12 September 2013 /Accepted: 14 January 2014 # Springer Science+Business Media Dordrecht 2014 Abstract The invasive Pacific red lionfish (Pterois positioned closer to and used limited shelter more when volitans) poses a threat to western Atlantic and Carib- paired with similarly sized lionfish and (2) grouper bean coral reef systems. Lionfish are small-bodied pred- moved much further away from shelter when paired ators that can reduce the abundance and diversity of with smaller lionfish. We also found that neither large native fishes via predation. Additionally, native preda- lionfish nor large Nassau grouper preyed upon smaller tors or competitors appear to have a negligible effect on individuals of the opposite species suggesting that Nas- similarly sized lionfish. Nassau grouper (Epinephelus sau grouper do not recognize small lionfish as prey. This striatus) are a regionally endangered, large predator study highlights how invasive lionfish may affect native found throughout lionfish’s invasive range. Because Nassau grouper, and suggests that competition for shel- lionfish and Nassau grouper occupy similar habitats ter between these two species may be size dependent. and use similar resources, there is potential for compe- tition between these two species. Using large, outdoor Keywords Avoidance . Bahamas . Refuge . Shelter in-ground tanks, we investigated how lionfish and Nas- dominance . Size dependence sau grouper affect each other’s behavior by comparing their distance from and use of shelter when in isolation versus when both species were in the presence of each Introduction other with limited shelter. We found that Nassau grou- per, which displayed a high affinity for shelter in isola- Marine biological invasions are increasingly common tion, avoided lionfish in two distinct ways; (1) groupers and result in many negative effects on native systems (Ruiz et al. 1997). Most marine invaders are inverte- : : brates; however, invasions of marine fishes can have W. W. Raymond M. A. Albins T. J. Pusack drastic ecological effects (Helfman 2007). The invasion Department of Zoology, Oregon State University, of Pacific red lionfish (Pterois volitans, Linnaeus, 1758) 3029 Cordley Hall, Corvallis, OR 97331-9214, USA is arguably the most serious marine fish invasion to date, Present Address: and its effects on native fish communities via direct W. W. Raymond (*) predation have already been well documented (e.g. Friday Harbor Laboratories, University of Washington, Albins and Hixon 2008; Albins 2013). However, there 620 University Road, Friday Harbor, WA 98250, USA e-mail: [email protected] has been little research on non-predatory interactions between invasive lionfish and native fish species. In Present Address: the present study we focus on the potential competitive M. A. Albins interactions between invasive lionfish and native Nas- School of Fisheries Aquaculture and Aquatic Sciences, Auburn University, sau grouper (Epinephelus striatus, Bloch, 1792) for 8300 State Highway 104, Fairhope, AL 36532, USA limited shelter space. Environ Biol Fish Lionfish were first recorded in Atlantic waters in the in the stomach contents of lionfish (Morris and Akins mid-1980s, and were likely introduced via aquarium 2009), and anecdotal reports have found lionfish in the releases or escapes (Morris and Whitfield 2009). Cur- guts of two species of large native groupers (Maljković rently, their established range includes the southeastern et al. 2008). Thus, intraguild predation may occur be- seaboard of the United States, the Gulf of Mexico, the tween lionfish and other native predators. In addition to Caribbean, and much of the tropical and sub-tropical predation, lionfish may also interact with large native Western Atlantic (Schofield 2009, 2010). Lionfish are predators via competition for shared resources, such as predicted to continue to expand southward along the food and shelter. Shelter space is an important, poten- east coast of South America (Morris and Whitfield tially limiting resource for coral-reef fishes (reviewed by 2009;Luizetal.2013). Throughout the invaded range, Hixon 1991). Field experiments show that shelter/ lionfish are found in diverse habitats, including coral refuge space can limit the local abundance of reef fishes and rocky reefs (Whitfield et al. 2007), seagrass beds (e.g. Hixon and Beets 1993) and can affect patterns of (Claydon et al. 2012), mangrove forests (Barbour et al. mortality in reef fishes (e.g. Forrester and Steele 2004). 2010; Claydon et al. 2012), estuaries (Claydon et al. However, there has been little research concerning com- 2012; Jud and Layman 2012), and mesophotic reefs petition for shelter between native and invasive marine (Lesser and Slattery 2011). Local populations of inva- fishes. sive lionfish exhibit exponential population growth Competition for shelter is often size dependent and (Albins and Hixon 2011; Claydon et al. 2008) and occur most research examining competition for shelter in ma- at far greater densities than lionfish in their native range rine and freshwater fishes has indicated that larger indi- (Green and Côté 2009;Kulbickietal.2012). Given their viduals are dominant (e.g. O’Niell and Cobb 1979; broad invasive range and high densities, lionfish have Shulman 1985; Buchheim and Hixon 1992;Figler the potential to interact with a wide variety of species et al. 1999; Vorburger and Ribi 1999; Nakata and across many different habitats (Côté et al. 2013). Goshima 2003). However, competitive interactions can Invasive lionfish have severe direct effects on native shift as the size of competitors change through their species, which may cause cascading indirect effects respective life spans (e.g. Sebens 1982; Wootton 1994; (Albins and Hixon 2011). They are known to consume Donahue 2004). In an invaded ecosystem it is likely that at least 41 native fish species in 21 families (Albins and native species will encounter varying size classes of the Hixon 2008; Morris and Akins 2009; Valdez-Moreno invader and therefore size-dependent relationships may et al. 2012). Moreover, lionfish in the Bahamas directly exist. Considering the documented patterns of compet- reduce the number of small reef-fishes on patch reefs by itive interactions between fishes it is critical to investi- up to 93 % over short time periods (Albins and Hixon gate varying size combinations of native and invasive 2008;Albins2013), and may reduce prey biomass by up species as a possible factor in competitive interactions. to 65 % (Green et al. 2012). This reduction in small reef- However, in at least one study of competition between fish abundance can be up to 2.6 times the reduction due native and invasive freshwater fishes, invaders to a native mesopredator, the coney grouper outcompeted natives for shelter regardless of size (Van (Cephalophous fulva, Linnaeus, 1758) (Albins 2013). Kessel et al. 2011). Additionally, lionfish predation on parrotfishes may A large bodied native predator that could potentially indirectly increase algal growth, leading to decreased compete with lionfish for shelter space is the Nassau coral cover, and possibly trophic cascades (Albins and grouper. Despite being severely overfished and region- Hixon 2011). This potential shift to algal dominated ally endangered throughout most of the greater Carib- habitats may already have occurred in mesophotic com- bean region (Cornish and Eklund 2003), Nassau grouper munities (Lesser and Slattery 2011). are relatively common in the Bahamas and are of high While previous studies have examined interactions ecological and economic importance (Sadovy and between invasive lionfish and native prey (Albins and Eklund 1999). Nassau grouper are known to behave Hixon 2008; Green et al. 2012;Albins2013) and be- aggressively towards conspecifics as well as other spe- tween lionfish and native mesopredators (Albins 2013), cies (Sadovy and Eklund 1999;Stallings2008). Further- interactions between lionfish and larger coral-reef pred- more, the presence of Nassau grouper has been shown to ators remain relatively understudied. Juvenile speci- have negative effects on the growth rate of native mens of large-bodied grouper species have been found mesopredators, such as small groupers (Stallings Environ Biol Fish 2008). Juvenile Nassau grouper, between 12 and 50 cm reported in 2005 (Albins and Hixon 2008). SCUBA total length (TL), tend to inhabit small patch reefs and divers used nets to collect lionfish and Nassau groupers rocky coral outcroppings and are known to use reef from surrounding shallow reefs (2–10 m depth). The TL holes for shelter (Beets and Hixon 1994; Eggleston of each fish was recorded, and the fish were transported 1995;SadovyandEklund1999). Invasive lionfish tend in coolers with seawater to PIMS, where they were held to inhabit similar habitats and also use reef holes for separately (by species) in 100 cm wide×100 cm long× shelter (Schultz 1986; Whitfield et al. 2007). Due to this 43 cm high cages submerged in large, outdoor, flow- overlap in habitat preference, shelter use, large popula- through seawater tanks. tions of lionfish around our study site, lionfish and Nassau grouper have the potential to compete for shel- Experimental design ter. Furthermore, Nassau groupers as well as other large Caribbean reef predators have been a logical potential We conducted all experimental trials in mesh cages source of biological control of the lionfish invasion. measuring 86 cm wide×258 cm long×43 cm high. Reports of lionfish in the guts of large groupers Two removable partitions divided these cages into three (Maljković et al. 2008) offer some support for this equal 86 cm wide×86 cm long×43 cm high areas to hypothesis but there is little other research regarding allow for both isolation and interaction periods in each predation on invasive lionfish. However, to date there trial (Fig. 1). We constructed shelters by placing two has been no direct documentation of grouper predation 20×20×20 cm cinder blocks end-to-end, creating one on lionfish in the wild.