Interactions Between Invasive Lionfish and Native Nassau Grouper
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Interactions Between Invasive Lionfish and Native Nassau Grouper
Wendel RaymondDr. Mark Hixon
Mark AlbinsTim Pusack
Kurt IngemenOSU HHMI 2010
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The Indo-Pacific Lionfish (Pterois volitans)
• Native to the Indo-Pacific• Maximum observed size: 38cm• Maximum observed depth: 55m • Average density: 80 individuals per
hectare• Eat fish and crustaceans• First sighted in southern Florida in late
1980’s and early 1990’s.
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Lionfish in the Invaded Range• Maximum observed size: 45cm• Maximum observed depth: 300m• Densities range from 21-390 individuals per hectare • Lionfish can reduce native juvenile reef fish abundances by 79%.
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Nassau Grouper (Epinephelus striatus)
• Nassau grouper is a native predator on Atlantic reefs
• Important to commercial and subsistence fisheries
• Little is known of the effects lionfish may have on Nassau groupers and vice versa
• Possible biological control
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Questions• Do lionfish and Nassau grouper
compete for shelter?
• Do large lionfish eat small Nassau grouper?
• Do large Nassau grouper eat small lionfish?
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Exuma Sound, Bahamas
Lee Stocking Island
Perry Institute for Marine Science
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Methods• Experiments were conducted in large in-ground tanks.• Single lionfish and Nassau grouper were placed in partitioned cage for a
24hr acclimation period.• Morning, midday and evening, positions were recorded so that distance
from shelter could be measured.• Three treatments at size ratios of 1:1, 1:4, 3:1 (lionfish:Nassau grouper).• Cinderblocks were used for shelter.
1 meter
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• After acclimation period, partitions and outer cinderblocks were removed.
• Recorded movements and behavior for 20 min.
• Morning, midday and evening, positions were recorded so that distance from shelter could be measured.
Methods
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Data Analysis
Before
After
Distance From Shelter (m)
Freq
uenc
y
Comparing random expected distance to observed distance
1:1 1:4
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Data AnalysisComparing random expected distance to observed distance
Before
After
1:1 1:4
Freq
uenc
y
Distance From Shelter (m)
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ResultsComparing random expected distance to observed distance
Before
After
1:1 1:4
p-value <0.05
p-value <0.01
Freq
uenc
y
Distance From Shelter (m)
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ResultsComparing before and after percentage of observations in shelter
Percentage of time spent in shelter hole for 1:1 Treatment
Percentage of time spent in shelter hole for 1:4 Treatment
Before After p-value
Lionfish 22.2% 14.3% 0.310
Nassau Grouper 81.0% 63.2% 0.159
Before After p-value
Lionfish 52.2% 58.9% 0.419
Nassau Grouper 65.6% 39.3% 0.137
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ResultsPredation
0
1
2
3
4
5
6
7
8
Large Lionfish with Small Grouper (3:1 Treatment)
Num
ber o
f Pre
datio
n ev
ents
0E. striatus Halichoeres bivittatus Haemulon sp.
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Results
0
1
2
3
4
5
6
7
8
Large Grouper with Small Lionfish
(1:4 Treatment)N
umbe
r of P
reda
tion
even
ts
Predation
0Halichoeres bivittatusP. volitans
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Conclusions• Do lionfish and Nassau grouper compete for shelter?
-Yes – Nassau grouper shifted away from shelter in the presence of lionfish• Do large lionfish eat small Nassau grouper?
-No – even though they quickly ate other species• Do large Nassau groupers eat small lionfish?
-No – even though they quickly ate other species
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Future Research
• Growth and persistence of lionfish and Nassau grouper when in the presence vs. absence of each other in the wild.
• Why don’t lionfish eat small Nassau groupers?
• Why don’t Nassau grouper eat small lionfish?
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Howard Hughes Medical InstituteOregon State University URISC ProgramDr. Kevin AhernDr. Mark HixonTim PusackMark AlbinsKurt IngemenJulia Lawson Sean HixonPerry Institute for Marine Science Staff and Interns
Acknowledgments
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Hixon Lab Bahamas Team 2010
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Lionfish Nassau GrouperBefore Removal 6.1cm 6.2cmAfter Removal 21.0cm 45.6cm
Mean Distance From Shelter in 1:4 Treatment