Feeding ecology of invasive lionfish (Pterois volitans)
in the Bahamian archipelago
James A. Morris Jr. & John L. Akins
Received: 24 February 2009 / Accepted: 7 October 2009 / Published online: 27 October 2009
#
US Government 2009
Abstract Feeding ecology of the lionfish (Pterois
volitans), an invasive species in the Western North
Atlantic, was examined by collecting stomach content
data from fishes taken throughout the Bahamian
archipelago. Three relative metrics of prey quantity,
including percent number, percent frequency, and
percent volume, were used to compare three indices
of dietary importance. Lionfish largely prey upon
teleosts (78% volume) and crustaceans (14% volume).
Twenty-one families and 41 species of teleosts were
represented in the diet of lionfish; the top 10 families of
dietary importance were Gobiidae, Lab ridae, Gram-
matidae, Apogonidae, Pomacentridae, Serranidae,
Blenniidae, Atherinidae, Mullidae, and Monacanthi-
dae. The proportional importance of crustaceans in the
diet was inversely related to size with the largest
lionfish preying almost exclusively on teleosts. Lion-
fish were found to be diurnal feeders with the highest
predation occurring in the morning (08:00–11:00).
Keywords Pterois
.
Diet composition
.
Stomach content
.
Invasive species
Introduction
The lionfishes, Pterois miles and P. volitans, (Hamner
et al. 2007; Morris 2009) are the first non-native
marine fishes to become established along the
Atlantic coast of the U.S. and the Caribbean. Adult
lionfish specimens are now found along the U.S. East
Coast from Cape Hatteras, North Carolina, to Florida,
and in Bermud a, the Bahamas, and throughout the
Caribbean, including the Turks and Caicos, Haiti,
Cuba, Dominican Republic, Puerto Rico, St. Croix,
Belize, and Mexico (Schofield et al. 2009). The first
documented capture of lionfish in the Atlantic was in
1985 off Dania Beach, Florida (J. Bohnsack, NOAA
NMFS, pers. comm.). Additional sightings occurred
in 1992 following an accidental release of six
lionfishes from a home aquarium into Biscayne Bay,
Florida (Courtenay 1995). Many other reports of
lionfish were documented in southeast Florida be-
tween 1999 and 2003 by Semmens et al. (2004), who
attributed many of these sightings to releases by home
aquarists.
Recreational divers reported the first sightings of
lionfish in the Bahamas in 2004 (REEF 2009). Snyder
and Burgess (2007) published the first record of
lionfish in the Bahamas, suggesting that lionfish were
widely distributed throughout Little Bahama and
Environ Biol Fish (2009) 86:389–398
DOI 10.1007/s10641-009-9538-8
J. A. Morris Jr. (*)
National Oceanic and Atmospheric Administration,
National Ocean Service,
National Centers for Coastal Ocean Science,
101 Pivers Island Road,
Beaufort, NC 28516, USA
e-mail: james.morris@noaa.gov
J. L. Akins
Reef Environmental Education Foundation,
98300 Overseas Hwy,
Key Largo, FL 33037, USA
Grand Bahama Banks. It is uncertain if lionfish
invaded the Bahamas via larval transport by ocean
currents or if their introduction was the result of
additional aquarium releases. Recent genetic studies
by Freshwater et al. (2009) suggest that lionfish
invaded the Bahamian archipelago via larval dispersal
originating from U.S. waters.
Early efforts to assess the density of lionfish off
North Carolina by diver surveys and remotely operated
vehicles suggested that lionfish populations were
rapidly increasing, with trophic interactions with native
reef fishes a concern (Whitfield et al. 2002;Hareand
Whitfield 2003). Recently, densities on Bahamian reefs
have been documented by Green and Côté (2009)tobe
in excess of 390 lionfish hectare
−1
;almostfivetimes
higher than estimates from the native range. Albins and
Hixon (2008) reported the first evidence of the impacts
of lionfish on native fish communities by demonstrat-
ing that lionfish reduced recruitment of coral reef fishes
on experimental reefs in the Bahamas by nearly 80%.
To date, comprehensive assessments of lionfish
diets are lacking in their native and invaded ranges.
Preliminary observations of lionfish feeding in their
native range suggest that lionfish feed primarily on
small fishes and some invertebrates (Fishelson 1975,
1997; Harmelin-Vivien and Bouchon 1976). In the
Pacific Ocean, the closely related luna lionfish
(P. lunulata) was found to feed primarily on inverte-
brates, including penaeid and mysid shrimps (Matsumiya
et al. 1980; W illiams and Williams 1986). More recently,
Albins and Hixon (2008) reported a list of nine species
consumed by invasive lionfish in the Bahamas. While
these observations suggest general patterns in lionfish
diet, quantitative assessments of lionfish feeding habits
in their new range are needed to elucidate the impacts of
these predators on invaded reef communities. The
overall objectives of this study were to 1) assess dietary
habits of lionfish collected from various habitats in the
Bahamian archipelago, 2) determine the relationship
between prey and predator size, and 3) document
temporal feeding patterns of this invader.
Methods
Collections
Lionfish were collected from the Bahamian archipel-
ago (Fig. 1) between January 2007 and May 2008. All
specimens were collected by fisheries professionals
and trained volunteers while snorkeling or using
SCUBA gear at sites (n=134) comprised of high
profile coral reefs, patch reefs, artificial reefs, man-
groves, and man-made canals ranging in depth from 1
to 30 m. Sampling sites were chosen opportunistically
to optimize sampling success. Most collections
utilized hand nets and vinyl collection bags, although
some were collected by pole spear. Live captures from
nets and bags were euthanized by excess anesthesia in
a bath of eugenol (Borski and Hodson 2003). Only
two lionfish regurgitated stomach contents during
ascension; therefore, stomach content retention meas-
ures were unnecessary. Lionfish were placed on ice
and dissected the same day as capture.
Lionfish were collected every month of the
calendar year (
X ¼ 111 28 individuals per month),
with the smallest sample size collected during June
(n=10) and the largest collected during February
(n=368). Collections of lionfish were achieved from
07:00 to 21:00; the majority of collections (99.1%)
occurred between 08:00 and 17:00.
Cumulative prey curve
A cumulative prey curve was used to assess sample
size su fficiency of lionfish stomachs containing
identifiable prey. Prey taxa were grouped by family
and cumulative numbers of novel prey were deter-
mined following 1,000 randomizations (Bizzarro et al.
2007). Mean and standard deviation of the cumulative
number of novel prey was calculated and sufficiency
of sample size was assessed statistically using the
linear regression method of Bizzarro et al. (2007) that
compares the slope from a regression of the last four
stomach samples to a slope of zero using a Student’s
t -test o f equality of two population regression
coefficients (Zar 1999). A p-value >0.05 was consid-
ered to demonstra te sampling sufficiency. To deter-
mine the minimum number of stomach samples (with
identifiable prey) required to adequately describe
lionfish diet, one sample was removed sequent ially
until the Student’s t-test p-value fell below 0.05
indicating that asymptote was not achieved.
Stomach content analyses
Stomach contents were identified to lowest possible
taxon (without fixation), counted, and measured for
390 Environ Biol Fish (2009) 86:389–398
total length (TL). No adjustment of prey TL due to
partial digestion was performed, thus the estimated
prey sizes are potentially underestimated. Volumes of
diet items taken from contents were measured by
water displacement in a graduated cylinder. The
contribution of each prey taxon to the overall diet
was assessed using t he following three relative
metrics of p rey quantity: percent frequency of
occurrence (%F), percent composition by numbe r
(%N), and percent composition by volume (%V)
(Hyslop 1980; Bowen 1996). Variations in prey size
and diet composition across lionfish sizes were
examined statistically by conducting a significance
test on the slope of a linear regression. An α-level
≤0.05 was considered significant.
Dietary importance indices or hybrid diet indi-
ces have been widely-employed in t he study of
fish food habits (Bowen 19 96 ), yet their speci fic
use has been criticized (Windell and Bowen 1978)
and subject to controversy (Hyslop 1980;Cortés
1997; Hansson 1998). For a robust assessment of
prey importance, three indices of importance were
calculated:
(1) the Index of Relative Importance (IRI) (Pinkas et
al. 1971 ),
IRI
a
¼ F
a
N
a
þ V
a
ðÞ
(2) the Index of Importance (IOI
a
) (Gray et al. 1997;
Hunt et al. 1999),
IOI
a
¼
100 F
a
þ V
a
ðÞ
P
s
a¼1
F
a
þ V
a
ðÞ
(3) the Index of Preponderance (IOP) (Natraj an and
Jhingran 1962; Sreeraj et al. 2006),
IOP
a
¼
F
a
V
a
P
s
a¼1
F
a
þ V
a
ðÞ
where s is the number of prey types, F
a
is the
frequency of occurrence of species a,V
a
is the percent
Fig. 1 Sampling locations and number of lionfish collected along the Bahamian archipelago
Environ Biol Fish (2009) 86:389–398 391
composition by volume of species a, and N
a
is the
percent composition by number of species a.
Results
The size of lionfish ranged from 62 to 424 mm TL with
a mean size (±SE) of 217±7 mm. A total of 1,876 prey
items from 1,069 stomachs were assigned to taxa.
Volumetric measurements of prey by taxon were
determined for 699 stomachs. Lionfish were sampled
from diverse habitat types including high profile coral
reefs (68%), canals (11%), artificial reefs (9%), other
(predominately blue holes) (5%), patch reefs (4%), and
mangrove habitats (3%). Cumulative prey curve analy-
sis indicated sample size sufficiency reached asymptote
for stomachs with identifiable prey (p>0.58). A large
number of stomachs were required to attain sufficient
sample size as p<.05 occurred at sample 706.
Prey composition
Tw enty-one families of teleosts, four families of
crustaceans, and one family of mollusks were repre-
sented in the diets of lionfish (Table 1). Teleost fishes
dominated lionfish diet comprising 78% by volume
(%V), 71.2% by number (%N), and 61.6% by
occurrence (%F). Crustaceans were also represented
at 14.4%V, 28.5%N, and 24.7%F, while mollusks
comprised <.01%V, %N, and %F. Approximately
21% (n=225) of the stomachs were empty.
Teleost prey included 41 species and exhibited a
wide-range of body shapes and morphological charac-
teristics (Table 1). The families with the greatest number
of species included Labridae (8), Pomacentridae (6),
Gobiidae (5), and Serranidae (4). Eight families com-
prised 38% of lionfish diet by volume and 48% of the
volume of identifiable teleosts. These included Poma-
centridae (7.2%), Labridae (6.7%), Mullidae (5.5%),
Grammatidae (5.0%), Serranidae (4.3%), Gobiidae
(4.2%), Apogonidae (3.6%), and Blenniidae (1.1%).
Unidentified prey accounted for 42.1%N, 38.1%V, and
36.5%F of all food items. The following teleost families
had the greatest representation in percent number:
Gobiidae (8.4%), Labridae (4.4 %), Grammatidae
(4.3%), Apogonidae (3.1%), Pomacentridae (1.8%),
Serranidae (1.5%), Blenniidae (1%), and Atherinidae
(1%). In terms of %F, the same familial order applied
with only minor changes in the percentages.
The majority of crustacea prey were ident ified as
shrimps: 25.5%N, 22.1%F, and 12.7%V of the total
prey. Of the remaining crustacean prey, 3%V, %F, and
%N were represented by four families (Corallanidae,
Squillidae, Rhynchocinetridae, Stenopodidae) along
with items from the categories of unidentified crab,
and unidentified crustaceans (Table 1).
Rankings of importance indices
The same ten families of teleosts ranked as the top ten
for all three indices (IRI, IOI, IOP) (Table 2). Top
three rankings (gobiids, labrids, and grammatids)
occurred in the IRI and IOP lists; whereas, the IOI
ranked labrids, pomacentrids, and gobiids as most
important of the teleost prey.
Diet composition and size of lionfish
The importance of teleosts in the diet of lionfish
increased significantly with size in all three dietary
metrics (%F R
2
=0.86, p=0.0003; %N R
2
=0.55,
p=0.02; %V R
2
=0.76, P=0.005) (Fig. 2). The mean
sizes of teleosts and crustaceans in the diet increased
with the size of lionfish (teleost prey R
2
=0.46, p=.01;
crustacean prey R
2
=0.36, P=0.002) (Fig. 3). The
maximum number of crustacean prey per lionfish was
50, whereas the maximum number of teleost prey was
21. The mean ratio of prey size (TL) to lionfish size
(TL) was 14.5%±0.003 standard error of the mean.
The maximum prey size was 48% of the total length
of lionfish, whereas the minimum prey size was
0.02%.
Feeding activity
Stomachs of lionfish contained the highest volume of
prey during the morning hours of 07:00–11:00 with a
significant decrease in mean prey volume towards the
evening (R
2
=−0.39, P=.01) (Fig. 4). Few lionfish
were collected at dusk or immediately after dark;
therefore the prevalence of feeding at this time is
uncertain.
Discussion
In the Bahamian archipelago, invasive lionfish feed
predominantly on teleosts and crustaceans. The large
392 Environ Biol Fish (2009) 86:389–398
Table 1 Identifiable lionfish prey sorted by taxa
Frequency (stomachs) %F (n=1,069) %N (n=926) %V (n= 699)
Mollusca 3
Unidentfied spp. 2 0.2 0.2
Octopodidae
Octopoda 1 0.1 0.1
Crustacea 264
Unidentified crustacean 2 0.2 0.2
Unidentified shrimp 236 22.1 25.5 13.8
Unidentified crab 8 0.7 0.9 0.5
Corallanidae 3 0.3 0.3
Stenopodidae
Stenopus hispidus 4 0.4 0.4
Rhynchocinetidae
Rhynchocinetes rigens 5 0.5 0.5 1.0
Squillidae 6 0.6 0.6 0.2
Teleosts 659
Unidentified fish 390 36.5 42.1 41.3
Atherinidae 9 0.8 1.0 0.6
Lutjanidae
Ocyurus chrysurus 1 0.1 0.1
Labridae 4 0.4 0.4 0.3
Thalassoma bifasciatum 13 1.2 1.4 0.6
Halichoeres pictus 2 0.2 0.2 0.7
Halichoeres bivittatus 3 0.3 0.3 1.1
Clepticus parrae 4 0.4 0.4 2.6
Halichoeres garnoti 13 1.2 1.4 1.9
Halichoeres maculipinna 1 0.1 0.1 0.1
Bodianus rufus 1 0.1 0.1
Xyrichtys sp. 1 0.1 0.1
Opistognathidae 3 0.3 0.3 0.3
Gobiidae 20 1.9 2.2 1.1
Coryphopterus personatus/hyalinus 39 3.6 4.2 1.6
Coryphopterus eidolon 14 1.3 1.5 1.5
Coryphopterus dicrus 3 0.3 0.3 0.4
Coryphopterus glaucofraenum 1 0.1 0.1
Priolepis hipoliti 1 0.1 0.1
Scaridae 2 0.2 0.2
Scarus iserti 3 0.3 0.3
Scarus viride 1 0.1 0.1 0.1
Blenniidae 1 0.1 0.1
Lucayablennius zingaro 4 0.4 0.4 0.1
Malacoctenus triangulatus 4 0.4 0.4 0.8
Malacoctenus boehlkei 1 0.1 0.1 0.3
Tripterygidae
Enneanectes sp. 1 0.1 0.1 0.1
Environ Biol Fish (2009) 86:389–398 393
