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Delineating Stock Boundaries: Pacific Green Turtles
Michael P Jensen
NRC Postdoc, Marine Mammal & Turtle Division
NOAA Fisheries, Southwest Fisheries Science Center
Review of NOAA Fisheries’ Science on Marine Mammals & Turtles
Southwest and Northwest Fisheries Science Centers
27-31 July 2015
La Jolla, CA
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DEFINING BOUNDRIES OF TURTLE STOCKS
IDENTIFYING UNITS TO CONSERVE
-Identify Management Units (MUs) - mtDNA
-Identify broader regional groupings (e.g. DPS).
CONNNECTIVITY BETWEEN FORAGING AND NESTING AREAS
-Identify the source populations of turtles sampled away from the nesting sites.
-Define boundaries of Management Units
ROOKERIES
FORAGING
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NMFS-SWFSC coordinating Global green turtle stock structure (mtDNA) survey:
• Approx. 4,400 rookery samples from 121 rookeries with mtDNA sequences completed.
• International collaboration needed to address information gaps.
AtlanticOcean
IndianOcean
PacificOcean
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Distribution of green turtle nesting beaches across the Pacific Ocean
• Most abundant species of marine turtles
• Widely distributed globally
Modified from Seminoff et al. 2015
USA
Australia
Pacific Ocean
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Australia
Pacific Ocean
Genetic sampling of green turtle nesting beaches across the Pacific Ocean
• >60 green turtle rookeries sampled (>2000 samples)• 41 genetic stocks or Management Units • Structure generally exists on a scale of >500 km• Gaps still exists
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USA
Australia
Pacific Ocean
Genetic sampling of green turtle foraging areas across the Pacific Ocean
• First study to use mixed stock analysis on green turtles in the Pacific was from Hawaii (Dutton et al. 2008).
• Found that 100% of turtles foraging in Hawaii were from the French Frigate Shoals with no outside contribution.
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Australia
Pacific Ocean
Genetic sampling of green turtle foraging areas across the Pacific Ocean
• 31 foraging areas sampled across the Pacific Ocean
• >4000 samples from foraging green turtles
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Mixed Stock Analysis using mtDNA• Bayesian analysis to estimate the contribution of known source
pops to a mixed aggregation• sensitive to genetic structure and coverage of source rookeries
Rookery 1 Rookery 2 Rookery 3
Mixture (e.g. foraging ground)
0
50
100
Rookery 1 Rookery 2 Rookery 3
Rookery 1 Rookery 2 Rookery 3
Mixture (e.g. foraging ground)
0
50
100
Rookery 1 Rookery 2 Rookery 3
25%
75%0%
25%
75%0%
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Australia
Pacific Ocean
Helen Reef, Palau• Green turtles foraging at Helen Reef originate from multiple
regional rookeries
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Australia
Pacific Ocean
The Mariana Islands• Most turtles (80%) are from the Marshall Islands 3000 km
away• 11 turtles (3%) were estimated to originate from the French
Frigate Shoals >4000km
RMI
CNMI/Guam
Yap
Ogasawara
PNGPalau
FFS
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Australia
Pacific Ocean
The Marshall Islands
• Most turtles originate from the Marshall Island rookery
• But Marshall Island green turtles also forage at distant FGs
RMI
CNMI/Guam
Yap
Ogasawara
PNGPalau
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The effects of ocean current on connectivity of green turtle habitat• In collaboration with Donald Kobayashi
Pacific Islands Fisheries Science Center
• Modelling hatchling dispersal to better understand recruitment patterns and improve mixed stock analysis. (Jensen, Dutton, Kobayashi).
• Release particles “virtual hatchlings” from rookeries and simulate passive drift for 3 years.
• Look at connectivity between release sites (rookeries) and foraging sites.
• Better understanding of hatchling dispersal routes.
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The Marshall Islands • Most turtles originate from the Marshall Island rookery
• No contribution from other regional rookeries.
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The Mariana Islands• Most turtles (80%) are from the Marshall Islands 3000 km
away• 11 turtles (3%) were estimated to originate from the French
Frigate Shoals >4000km
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Australia
Pacific Ocean
MSA for individual foraging areas• We now have specific information on connectivity between
rookeries and 30 feeding grounds across the Pacific.
• Detailed information of connectivity that show highly variable patterns influenced by rookery size, distance and ocean currents.
• Provide important information for management.
Australia
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Australia
Pacific Ocean
Boundaries of green turtle stocks in relation to DPSs
• Connectivity between rookeries and FGs within and across proposed DPSs.
• We can look at which DPS are impacted by impacts on foraging areas or in fisheries.
USA
Australia
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Boundaries of green turtle stocks-MSA 20 foraging areas across the Pacific Ocean
Co
ntr
ibu
tio
n in
%
0%10%20%30%40%50%60%70%80%90%
100%
Ash
mo
re R
eef
Fog
Bay
Co
bo
rgh
Pen
insu
la
Fiel
d Is
lan
d
Aru
Sir
Edw
ard
Pel
lew
Man
tan
ani
Torr
es S
trai
t
Cla
ck R
eef
Ho
wic
ks
Edge
com
be
Bay
Sho
alw
ater
Bay
Mo
reto
n B
ay Fiji
Am
eric
an S
amo
a
Am
eric
an S
amo
a LL
RM
I
Pal
au
CN
MI
FFS
Co
lom
bia
DPS 6 DPS 7 DPS 8 DPS 9 DPS 10 DPS 11
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American Samoa Longline Fishery
• Impacting green turtle rookeries from multiple DPSs• Highly predictable by ocean current simulations
Australia
American Samoalongline fishery
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American Samoa Southern GBR
French Polynesia
Galapagos
Northern GBR
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A wealth of cool information
Ocean current simulation shows great promise as an additional tool to look at things like;
• Assess the connectivity of yet unsampled rookeries• Improve msa models by using ocean modeling data as prior
information
Mixed Stock Analysis gives insight into detailed population dynamics;
• Recruitment patterns for different age-classes (Jensen et al. in press).
• Combining hormone assays to look recruitment patters for male and female green turtles (Jensen and Allen in prep).
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Thanks for listening!
Acknowledgments
IndianOcean
PacificOcean