Lionfish Prey Preference Between Native Basslets

AN ABSTRACT OF THE THESIS OF

Emily R. Anderson for the degrees of Honors Baccalaureate of Science in Biology presented on May 20, 2014. Title: Lionfish Prey Preference between Native Basslets.

Abstract Approved: ______Mark Hixon

The lionfish (Pterois volitans) is a successful invasive predator with large impacts on native fish populations in the western Atlantic. Lionfish predation may affect competition between prey species so it is important to understand whether lionfish display preferences between prey species. I investigated lionfish and native graysby grouper prey preference between prey species and prey size using two closely-related and potentially competitive prey species, the fairy basslet and blackcap basslet. In paired choice tests in aquaria, I recorded the first basslet hunted, total number of strikes, and total time spent hunting on each basslet as quantifications of preference. Lionfish initially hunted fairy basslet while graysby initially hunted blackcap basslet but neither predator displayed any preference between species in number of strikes or time spent hunting. Across all variables, lionfish preference shifted from small to large basslets as lionfish size increased, consistent with being a gape-limited predator, while graysby of all sizes tested preferred only large basslets. Brighter coloration and higher activity level of fairy basslet may have influenced lionfish initial preference but it is unclear why graysby initially hunted blackcap basslet. Lionfish initial preference may alter competition between the two basslet species if initial preference leads to increased fairy basslet mortality.

Key Words: Invasive Species, Lionfish, Graysby, Prey Preference

Corresponding e-mail address: [email protected]

Lionfish Prey Preference between Native Basslets

Emily R. Anderson

A PROJECT

submitted to

Oregon State University

University Honors College

in partial fulfillment of the requirements for the degrees of

Honors Baccalaureate of Science in Biology (Honors Scholar)

Presented May 20, 2014 Commencement June 2014

Honors Baccalaureate of Science in Biology p of Emily R. Anderson presented on May 20, 2014.

APPROVED:

______Mark Hixon, Mentor, representing Integrative Biology

______Sally Hacker, Committee Member, representing Integrative Biology

______Tye Kindinger, Committee Member, representing Integrative Biology

______Virginia Weis, Chair of the Department of Integrative Biology

______Toni Doolen, Dean, University Honors College

I understand that my project will become part of the permanent collection of Oregon State University, University Honors College. My signature below authorizes release of my project to any reader upon request.

______Emily R. Anderson, Author

ACKNOWLEDGMENTS

I would like to thank my parents, Scott and Jacqueline Anderson, for their support of my academic pursuits. I would thank my mentor, Dr. Mark Hixon, for his guidance over the last two years and for providing me with the opportunity to conduct research at the undergraduate level. I would also like to thank Dr. Sally Hacker as my advisor, for serving on my committee, and for her assistance in the thesis process. I express sincere gratitude to the members of Dr. Hixon’s lab Casey Benkwitt, Alex Davis, Lillian Tuttle for their aid and guidance while performing the experimental portion of my thesis and in particular I would like to thank Tye Kindinger as a member of my committee and for all the help, advice, and critiques throughout this process. Finally, I would like to acknowledge Oregon

State University’s College of Science Summer Undergraduate Research Experience grant for supporting funding for this project.

TABLE OF CONTENTS

Page

INTRODUCTION………………………………………………………………………..1

METHODS……………………………………………………………………………….4

Study area and fish collections……………………………………………...... 4 Experimental Design……………………………………………………..……....4 Statistical Analysis…………………………………………………………...... 7

RESULTS………………………………………………………………………………...8

DISCUSSION………………………………………………………………………...... 18

BIBLIOGRAPHY………………………………………………………………………23

APPENDIX……………………………………………………………………………..27

LIST OF FIGURES

Figure Page

Fig. 1. (Left) fairy basslet (Gramma loreto); (Right) blackcap basslet (Gramma melacara). The two species are normally similarly-sized. Blackcap basslet photo credit: www.finaddictsaltwaterfish.com, fairy basslet photo credit: Emily R. Anderson …………………………………..………………………………………..6

Fig. 2. The configuration of the experimental acrylic aquarium tank during the acclimation period. The grey panel represents an opaque metal barrier separating the basslets within glass containers with mesh covers from the predator...... 6

Fig. 3. Initial hunting preference of lionfish, varying in total length, when presented with (A) two different basslet species (n=16 lionfish) and (B) two basslets differing in size (n=17 lionfish)………………...... 12 Fig. 4. Initial hunting preference of graysby, varying in total length, when presented with (A) two different basslet species (n=11 graysby) and (B) two different basslet sizes (n=12 graysby)...... 13 Fig. 5. Attack preference (mean ± SE) of lionfish, varying in total length, when presented with (A) two different basslet species (n=16 lionfish) and (B) two basslets differing in size (n=17 lionfish)………………………………………….14 Fig. 6. Attack preference (mean ± SE) of graysby, varying in length, when presented with (A) two different basslet species (n=11 graysby) and (B) two basslets differing in size (n=12 graysby)….……………………...... 15

Fig. 7. Overall hunting preference (mean ± SE) of lionfish, varying in total length, when presented with (A) two different basslet species (n=16 lionfish) and (B) two basslets differing in size (n=17 lionfish).…………………………………………16

Fig. 8. Overall hunting preference (mean ± SE) of graysby, varying in total length, when presented with (A) two different basslet species (n=11 graysby) and (B) two basslets differing in size (n=12 graysby)………...... 17 Lionfish Prey Preference between Native Basslets

Introduction

Invasive species can have drastic ecological effects on native ecosystems (Mack et al. 2000, Pejchar and Mooney 2009). They can alter the trophic balance within these systems (Salo et al. 2007) causing environmental and economic damage, the cost of which, although difficult to quantify, can also be very large (Pimentel et al. 2005, Pejchar and Mooney 2009). Some of the most pronounced effects of non-native species on ecosystems are due to invasive predators (Mack et al. 2000, Davis 2003). Invasive predators can have stronger impacts on native prey populations than native predators

(Fritts et al. 1998, Salo et al. 2007) and can further alter prey communities by inducing changes in normal predator avoidance behavior (Sih et al. 2010, Bourdeau et al. 2011), exploiting ineffective or complete lack of anti-predatory responses (Cox and Lima 2006,

Sih et al. 2010, Kovacs et al. 2012), and by competing with and even consuming native predators (Green et al. 2012).

The red lionfish, Pterois volitans, is a notable example of an invasive predator.

Native to the Indo-Pacific, lionfish were first recorded in the western Atlantic in the mid

1980’s (Morris and Whitfield 2009) and are now established along the southeastern coast of the United States up to North Carolina, throughout the Gulf of Mexico, in the

Caribbean down to Venezuela (Lasso-Alcalá and Posada 2010), and are expected to invade as far south as Uruguay (Morris and Whitfield 2009, Schofield 2010, Luiz et al.

2013). Lionfish occur in higher densities in the western Atlantic than in their native range (Côte et al. 2013) and have large impacts on native fish populations and 2 recruitment, reducing the number of small-reef fish on patch reefs by over 90% (Albins and Hixon 2008, Green et al. 2012, Albins 2013). They have been found to consume a broad range of native reef fishes including at least 76 fish species within 26 families

(Morris and Akins 2009, Green et al. 2012, Valdez-Moreno et al. 2012), and their effects on native fish populations are up to 2.6 times greater than an ecologically-similar native predator, the coney grouper (Cephalopholis fulva, Albins 2013). Effects of lionfish on reef-fish populations as a whole have been well documented (Albins and Hixon 2008,

Green et al. 2012, Albins 2013, Côté et al. 2013) and lionfish are known to consume prey species that are also potential competitors, such as the fairy basslet and blackcap basslet

(Morris and Akins 2009), but there is little research on how lionfish predation may affect competition between these closely-related prey species. It is unlikely that even with heavy removal efforts that lionfish can be completely extirpated (Barbour et al. 2011), therefore it is important to fully understand the ecological effects of lionfish in their new introduced range

Investigating potential preferences in prey selection of invasive lionfish is important, because it can lead to a better understanding of how of preference may affect potentially competing prey species. Fairy basslet (Gramma loreto) and blackcap basslet

(Gramma melacara) are two closely-related prey species of the invasive lionfish (Morris and Akins 2009) that normally co-occur on reef ledges at depths of 30 – 50 meters

(Böhlke and Randall 1963). Intraspecific competition for feeding position on reef ledges, involving exploitative and interference competition, has been reported in fairy basslet populations where large basslets positioned near the front of the ledge, the prime feeding location, show aggressive interactions to basslets of the same size or smaller, forcing the 3 smaller basslets backwards to positions with less food access (Webster and Hixon 2000).

Since fairy and blackcap basslet overlap in diet and habitat, and there is within-species competition reported in fairy basslet for feeding position, it is likely that where the two basslet species co-occur, there is interspecific competition for feeding position as well.

Predation may affect competitive interactions between species (Chase et al. 2002), so lionfish prey preference, if different from that of native predators, could alter competition between basslet species, potentially giving one species an advantage if there is preferential hunting and consumption of the other. Lionfish preferences matching those of native predators could also alter competition by exacerbating the effects of predation already acting on basslet competition. If lionfish lack a preference between the basslet species, mortality of both species could rise.

This study focused on examining the following questions: (1) Do invasive lionfish display a preference between two closely-related prey species, fairy basslet and blackcap basslet? (2) Do lionfish display a preference between small and large basslets?

(3) Does lionfish size affect prey preference? (4) Are these preferences different from that of an ecologically-similar native predator? I conducted a series of controlled experiments in acrylic aquaria to determine the prey preference of invasive lionfish and native graysby (Cephalopholis cruentata) between the two similar native prey species: fairy basslet and blackcap basslet.

Methods

Study area and fish collections

I conducted this study during August 4 – 31, 2014 at the Cape Eleuthera Institute on Eleuthera, Bahamas. Lionfish, fairy basslet (Fig. 1A), blackcap basslet (Fig. 1B), and graysby were collected from patch reefs in Exuma Sound and Rock Sound of Eleuthera by SCUBA and snorkel divers using hand nets and the fish anesthetic quinaldine.

Additional graysby were caught with hand fishing line using either squid or silverside fish as bait. Off of Eleuthera fairy basslet and blackcap basslet co-occurr on reefs shallower than previously reported, so basslets were collected from reefs at 15 meters deep or shallower in the Exuma Sound. Graysby and lionfish were collected from patch reefs in Rock Sound shallower than 5 meters. To test a range of predator sizes, I collected lionfish and graysby ranging from the smallest up to the largest size that were present on the patch reefs. I collected a total of 20 lionfish ranging in size from 5.7 to

20.9 cm total length (TL) and 15 graysby ranging in size from 10.0 to 20.3 cm TL. Prior to each experiment, graysby and lionfish were starved for 24 hours to ensure the predators would respond to the presented prey.

(A) (B) Experimental Design

All trials were conducted in 50 gallon (91.5 cm long x 38 cm wide x 51 cm high) acrylic aquarium tanks with continuous flow-through saltwater systems. To observe predator feeding behavior and any preference for different prey, I placed individual basslets in glass containers with a mesh cover. This allowed predators to receive visual and chemical cues from the prey. I placed one basslet in each corner at one end of the 5 tank, and placed a predator (lionfish or graysby) on the other side of the tank, separated from the basslets by a barrier (Fig. 2). To test whether the relative size of basslets affect predator preference, I used two different size classes of basslets: small (1.5 – 2.5 cm) and large (> 3.5 cm). Basslet treatments consisted of the following combinations of basslet species and size on each predator: (1) small fairy vs. large fairy, (2) small blackcap vs. large blackcap, (3) small fairy vs. small blackcap, (4) large fairy vs. large blackcap, (5) small fairy vs. large blackcap, and (6) large fairy vs. small blackcap. The order in which treatments were presented to each predator was randomized as well as the corner of the aquarium in which the basslets were placed when presented to predators.

After a 20 minute tank acclimation period, I removed the barrier between the predator and basslets, and observed the predator for ten minutes. I recorded which basslet the predator hunted first (initial hunting preference), any predatory strikes at basslets in which the mouth of the predator made physical contact with the glass (attack preference), and the total amount of time the predator spent hunting each basslet (overall hunting preference). Lionfish were considered to be hunting when they were facing a basslet, flaring the pectoral fins, and blowing pulsed jets of water at the basslet while slowly moving within striking distance (Albins and Lyons 2012). I characterized graysby hunting behavior as being when an individual was positioned close to and directly facing a basslet (Webster 2004). If a predator did not display hunting behavior towards either basslet, the trial was recorded as “no response”. For logistical purposes, whenever possible I used digital cameras placed outside the tanks in order to personally observe one tank and video record the second tank simultaneously. At the conclusion of the experiment, all native fishes were released back to the ocean and all lionfish were 6 euthanized according to all Institutional Animal Care and Use Committee (IACUC) regulations.

Statistical Analysis

When making comparisons in the initial hunting preference, attack preference, and overall hunting preference of predators between basslet species, only the four basslet treatments in which predators were presented with the two different basslets were analyzed. The four treatments in which predators were presented with two different sized basslets were used in analyses when making comparisons in preferences between basslet sizes. If a predator showed no response during any of the respective four treatments the individual was dropped from the analysis. Number of predators included in basslet species analyses: graysby n=11, lionfish n=16; in basslet size analyses: graysby n=12, lionfish n=17. Lionfish and graysby trial data were analyzed separately.

To test for differences in initial preference of predators between basslet species and between basslet size categories, I used a McNemar test with continuity correction, a chi-square test for correlated responses, due to the repeated measures in the experimental design. To test for differences in initial hunting preference, attack preference, and overall hunting preference across the predators’ size range, I used generalized estimation equations (GEEs) with exchangeable correlation structures to account for the repeated measures in the experimental design. GEEs are an extension to the generalized linear model approach that allow for correlations between observations from the same subject

(Liang and Zeger 1986). I used GEEs with binomial distributions when testing for differences in initial hunting preference across the predator size range because of the binary response variables, and GEEs with Poisson distributions were used when testing for differences in attack preference and overall hunting preference to assess the 8 interactive vs. additive effects of predator size and basslet species or size. To find the best fit equation, I calculated QIC and quasi-likelihood values comparing the interactive and additive GEEs and chose the equations with the lowest values (Pan 2001). All statistical analyses were conducted using R version 3. 0. 1 (R Development Core Team

2013) with the associated package geepack (Halekoh et al. 2006).

Results

There was a clear pattern for both lionfish and graysby in initial hunting preference of both basslet species and basslet sizes. Lionfish initially hunted fairy basslet significantly more frequently than blackcap basslet (McNemar chi-square = 96.01, p <

0.0001), and this preference did not significantly differ among lionfish sizes (Fig. 3A; coefficient estimate = -0.02 ± 0.06, W = 0.13, p = 0.716). Lionfish size had a moderately significant effect on initial hunting preference of prey sizes (coefficient estimate = 0.11 ±

0.05, W = 5.11, p = 0.024). As lionfish size increased, the initial hunting preference of lionfish shifted from small to large basslets (Fig. 3B). Graysby initially hunted blackcap basslet (Fig. 4A, McNemar chi-square = 62.02, p < 0.0001) and large basslets (Fig. 4B,

McNemar chi-square = 32.03, p < 0.0001) more frequently and these preferences were not significantly affected by graysby size (coefficient estimate = -0.05 ± 0.14, W = 0.14, p = 0.71; coefficient estimate = -0.14 ± 0.14, W = 1.01, p = 0.31, respectively).

Lionfish did not display any attack preference between basslet species (Fig. 5A; coefficient estimate = -0.67 ± 0.38, Wald=3.05, p=0.081) across the lionfish size range

(coefficient estimate = -0.04 ± 0.03, Wald=1.58, p=0.209). Total number of strikes an 9 individual lionfish made during the 10 minute trials where the basslet species differed ranged from no strikes at any basslets, despite displaying hunting behavior, to a maximum of 11 strikes at fairy basslet and 4 strikes at blackcap basslet. There was a significant interaction between lionfish size and basslet size in lionfish attack preference

(coefficient estimate = -2.67 ± 0.07, Wald=14.09, p<0.001), where increases in lionfish size resulted in a decrease in the mean number of strikes on small basslets and an increase in strikes on large basslets (Fig. 5B). The total number of strikes by lionfish ranged from

0 to 11 at large basslets and 0 to 5 at small basslets. Graysby did not have any significant attack preference between basslet species nor across the graysby size range (Fig. 6A; coefficient estimate = -0.05 ± 0.09, Wald = 0.31, p = 0.58; coefficient estimate, Wald =

0.18, p = 0.67, respectively), and consistently struck at large basslets regardless of graysby size (Fig. 6B; coefficient estimate = -1.79 ± 12.59, Wald = 12.59, p < 0.001; coefficient estimate = -0.06 ± 0.07, Wald = 0.69, p = 0.40447, respectively). Total number of strikes in graysby trials with different basslet species ranged from 0 to 8 at fairy basslet and 0 to 15 strikes at blackcaps. Total strikes during trials with different sized basslets ranged from 0 to 15 at large basslets and 0 to 6 at small basslets.

Lionfish and graysby displayed different attack behavior: when lionfish struck at a basslet, there was a minimum of two seconds before another strike while graysby often struck at a basslet multiple times in quick succession, striking the glass container up to nine times in three seconds. As lionfish neared the basslet they also directed jets of water at the basslet (see Albins and Lyons 2012), the blowing appeared to increase in frequency as the lionfish approached the basslet. Both predators made few subsequent strikes once they made physical contact with the glass container, yet switching hunting behavior 10 between basslets was observed more often in lionfish than in graysby. In the 18 video recorded lionfish trials, lionfish switched which basslet was being hunted a total of 31 times while graysby switched a total of 6 times in 16 video recorded trials. 17 of the 31 lionfish switches were associated with movement of the basslet not being hunted, where lionfish would shift from hunting one basslet to the other if the basslet not being hunted moved. None of the 6 graysby switches observed were correlated with basslet movement.

The two basslet species often displayed different behaviors: blackcap basslets often remained inactive throughout the 10-minute trial and either remained resting on the bottom of the container or pressed motionless against the mesh at the top. Fairy basslets were generally more active, hovering in the center of the container. Both basslet species became highly active during a graysby attack, quickly darting around the glass container.

Once the attack ceased, the basslet either settled at the bottom of the container or remained still against the mesh top. Basslets rarely reacted to lionfish hunting behavior or strikes, usually continuing to hover or remain still, and never displayed the same rapid movements that were elicited by a graysby attack.

Overall hunting preference of lionfish did not significantly differ among lionfish size nor between basslet species (Fig. 7A; coefficient estimate = -0.05 ± 0.03, Wald =

2.85, p = 0.091; coefficient estimate = -0.13 ± 0.25, Wald = 0.29, p = 0.588, respectively). Lionfish preference between basslet sizes significantly depended on lionfish size (coefficient estimate = -0.22 ± 0.07, Wald=9.82, p=0.002), with smaller lionfish spending more time hunting small basslets and larger lionfish spending more time hunting large basslets (Fig. 7B). Total lionfish hunting time during trials with 11 different basslet species ranged from 2 to 555 seconds (out of 600 seconds) directed at fairy basslets and 6 – 599 seconds directed at blackcap basslets. In trials with different basslet sizes, lionfish total hunting time ranged from 2 to 580 seconds on large basslets and 2 – 568 seconds on small basslets. The individual with the maximum number of strikes hunted for a total of 252 seconds (all directed at a large fairy basslet) while the individual with the longest hunting time made a total of three strikes.

Graysby did not have an overall hunting preference for a basslet species (Fig.

8A), with no significant difference in the total amount of time spent hunting either species (coefficient estimate = 0.21 ± 0.50, Wald = 0.18, p = 0.67). However, graysby overall hunting preference was significantly lower for small basslets (Fig. 8B; coefficient estimate = -1.21 ± 0.39, Wald = 9.68, p = 0.002). Neither the overall hunting preference of graysby for basslet species nor size significantly differed among graysby sizes

(coefficient estimate = -0.08 ± 0.15, Wald = 0.26, p = 0.608; coefficient estimate = 0.02 ±

0.07, Wald = 0.10, p = 0.746). Graysby total hunting time during trials with different basslet species ranged from 1 to 244 seconds on blackcap basslets and 2 – 65 seconds on fairy basslets. Total hunting time during trials with different basslet sizes ranged from 2 to 205 seconds on a large basslet, and 100 seconds on a small basslet. The maximum graysby hunting times for both large and small basslets were from the same individual during the same trial, which was also the individual and trial with the maximum number of graysby strikes (16), as well as the maximum number of strikes in succession (i.e., 9).

About 2/3 of the overall time spent hunting and 15 out of the 16 strikes in this graysby trial were directed at a large blackcap basslet.

Fig. 4. Initial hunting preference of graysby, varying in total length, when presented with (A) two different basslet species (n=11 graysby) and (B) two different basslet sizes (n=12 graysby).

Fig. 5. Attack preference (mean ± SE) of lionfish, varying in total length, when presented with (A) two different basslet species (n=16 lionfish) and (B) two basslets differing in size (n=17 lionfish).

Fig. 6. Attack preference (mean ± SE) of graysby, varying in length, when presented with (A) two different basslet species (n=11 graysby) and (B) two basslets differing in size (n=12 graysby).

Discussion

Piscivorous marine predators often preferentially distinguish prey items by size

(Floeter and Temming 2003, Hambright 2011) or by species (Almany et al. 2007).

Piscivorous predators may select the most abundant prey species but preferential selection of rare prey has been observed in predatory reef-fishes (Almany and Webster

2004, Almany et al. 2007). Size preferences are often due to factors such as the predator’s mouth size and the prey body depth or length since piscivores swallow prey whole (Hambright 2011). Both lionfish and graysby displayed no attack or overall hunting preferences between basslet species, which is consistent with observations of generalist predatory behavior in lionfish (Côté et al. 2013) and graysby (Randall 1967).

All response variables indicated that lionfish displayed a preference between basslet sizes showing a shift from small to large basslets as lionfish size increased, while graysby preferred only large basslets across their size range. However, due to the restricted graysby size range tested, it is possible smaller graysby may have had a consistent response to basslets as lionfish of corresponding size. Other studies have found that as marine predator size increases, they prefer to hunt larger prey (Schmitt and Holbrook

1984, Floeter and Temming 2003), potentially because there is greater profit of hunting larger prey with only minimal cost increases (Werner and Hall 1974). Therefore it is not unusual that graysby and lionfish, larger than 10 cm, preferentially hunted large basslets.

Like most piscivorous predators (Hambright 2011), lionfish and graysby are gape-limited in the size of prey they consume. Small lionfish preferentially hunted small basslets likely because the large basslets may have been close to, or larger than what the small lionfish were capable of ingesting. 19

While neither lionfish nor graysby displayed any attack preference or overall hunting preference between basslet species, they both had clear initial hunting preferences. Lionfish initially hunted fairy basslet more while graysby initially hunted blackcap basslet more. Coloration is the most obvious difference between fairy and blackcap basslets: fairy basslets with a purple anterior, yellow posterior, and a dark diagonal line through the eye compared to blackcap basslets with a purple body and black diagonal cap (Fig. 1). Most reef-fish have color vision, with two or three types of visual pigments (McFarland 1991, Cheney et al. 2013) which allow them to distinguish between colors (Cheney et al. 2013). It is likely that lionfish and graysby are able to visually distinguish fairy basslets from blackcap basslets and this distinction may have been a factor in initial prey preference. On reefs color may also play an important role since as depth increases red light lost, darkening many colors, but yellow remains quite visible meaning fairy basslets may remain more conspicuous.

Basslet behavior is another cue that may have drawn the initial attention of each predator. Fairy basslet were generally more active than the blackcap basslet which may explain why lionfish were more often initially attracted to the lionfish; lionfish may have been reacting to movement. I frequently observed that if the basslet not being hunted by the lionfish moved, the lionfish would often shift to hunting that basslet consistent with the hypothesis that prey movement stimulates hunting behavior. Since there was not any available prey-refuge habitat, such as a ledge, under which basslets are normally found

(Webster 2004), these different behaviors displayed by the two basslet species could be attributed to the laboratory setting. The bright yellow of the fairy basslet combined with 20 their more active behavior may have been more attractive to lionfish than the darker and less active blackcap basslet during the laboratory experiment.

The initial prey preference of graysby for blackcap basslets was surprising not only because they are generalist predators, but also because all the graysby used during the experiment were collected from patch reefs at 5 meters or shallower and distant from deeper reefs, meaning that they had possibly never been exposed to a blackcap basslet which I observed only at reefs 13 – 15 meters deep. Basslet behavior, coloration, body shape, and olfactory cues may all play a role in preference, but it is unclear why graysby initially hunted blackcap basslet more. Future studies should examine the possible mechanisms of preference, including the extent that prey coloration, behavior, and olfactory cues play in predators’ initial prey preference.

Lionfish appeared to be more persistent than graysby in their attacks; lionfish displayed stalking hunting behavior rather than a quick ambush attack like the graysby and the maximum lionfish hunting time was over twice that of the maximum graysby hunting time. On reefs, lionfish predation success is surprisingly low considering the large impacts they have on native reef-fish populations but is similar in both their introduced and native oceans, ranging from 22.9 – 51.2% (Cure et al. 2012), meaning that lionfish successfully consume prey only half of the time they strike at prey in both their native and invasive range. Since the predators could not consume the basslets in this experiment, predation success could not be determined, yet, the relatively low hunting success rates of lionfish on reefs may explain such persistence in hunting. Graysby predation success has not been assessed before but graysby may be more successful as an ambush hunter than lionfish and therefore potentially need not be as persistent. Time 21 budgets of hunting graysby on reefs could determine whether graysby predation success is greater than lionfish. Predator hunting behaviors may have been affected by the laboratory setting; failed strikes at the basslets in glass containers seemed to deter further strikes. Switches in hunting between prey was observed in both predators but was more common in lionfish. This behavior may be due to the artificial environment present in the experiment; once the predator struck the glass without consuming the prey, the situation became artificial.

Basslets commonly displayed different behaviors in response to attacks by lionfish compared to graysby attacks. Both basslet species became highly active during a graysby attack but made no response to a lionfish attack. This lack of response may be an indication of prey naïveté, where prey species lack an appropriate anti-predatory response due to a lack of historical predation (Cox and Lima 2006). The basslets displayed what appeared to be an anti-predator escape response during graysby attacks, but no such response was elicited by a lionfish attack. As an invasive predator with no morphologically-similar species in the Atlantic, lionfish may be benefiting from the potential naïveté of prey (Kovacs et al. 2012).

Conducting prey preference trials in a lab can be useful in understanding whether any preference exists (Rodgers 1990) but studies of lionfish hunting behavior in the field should be conducted to understand whether an initial hunting preference of fairy basslet will alter the populations of the two basslet species. These two species of basslets are normally segregated by depth (Böhlke and Randall 1963) and co-occur only on reefs in a small region. Future studies should consider whether lionfish, initially attracted to fairy basslet, will continue to hunt fairy basslet if there is a group of them close by, and 22 whether this will increase fairy basslet mortality compared to blackcap basslet, possibly giving blackcap basslet a competitive advantage. Further research examining potential lionfish initial preferences for other prey species are warranted. Ecologically important fishes, such as juvenile native predators (Serranidae) and parrotfishes (Scaridae), are also prey for lionfish, but it is unknown whether lionfish display any preferences among these prey. Since invasive predators can already have larger effects on prey than native predators (Fritts et al. 1998, Salo et al. 2007), their preferred prey may be negatively affected even more, causing possible cascading effects in the coral-reef ecosystem.

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APPENDIX

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