Day 3 07 Climate Change Tuna P. Lehodey

Report
th
7
SPC HOF meeting
Noumea, 28 Feb -4 Mar
VULNERABILITY OF OCEANIC FISHERIES IN
THE TROPICAL PACIFIC TO CLIMATE CHANGE
Patrick Lehodey1, John Hampton2, Rich W Brill3, Simon Nicol2,
Inna Senina1, Beatriz Calmettes1, Hans O Pörtner4, Laurent
Bopp5, Tatiana Ilyina6, Johann D Bell2 and John Sibert7
1 Space
Oceanography Division, CLS, France; 2Oceanic Fisheries Programme, SPC, New Caledonia; 3University of Miami, USA;
4Alfred Wegener Institute, Bremerhaven, Germany; 5CEA / IPSL, Paris, France; 6 Max Planck Institute for Meteorology, Germany;
7 Pelagic Fisheries Research Program, USA
Tuna and fisheries in the tropical Pacific O.
Katsuwonus pelamis
Skipjack
Thunnus albacares
Yellowfin
Tropical sp.
Bigeye
Temperate sp.
(Bluefin)
Albacore
Thunnus alalunga
Thunnus obesus
Distribution of tuna catch
60
- 20
- 30
- 40
- 50
- 60
- 70
- 80
- 90
- 100 - 110 - 120 - 130 - 140 - 150 - 160 - 170 180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
- 10
- 20
60
50
50
40
40
ICCAT
30
IATTC
WCPFC
20
30
20
10
10
0
0
- 10
- 10
IOTC
- 20
- 20
- 30
- 30
- 40
- 40
- 50
yellowfin
- 60
- 20
- 30
- 40
- 50
Total prises 90-97
- 60
- 70
- 80
skipjack
- 90
bigeye
- 100 - 110 - 120 - 130 - 140 - 150 - 160 - 170 180
YFT
BFT
SKJ
ALB
BET
170
bluefin
albacore
160
150
140
130
120
110
8000
WCPFC
Tuna
catch
in the WCPC
Catch
in WCPO
100
90
80
70
60
50
40
30
20
- 50
10
0
- 10
- 60
- 20
Projection under IPCC scenarios
IPSL Earth Climate Model
Atmospheric CO2 concentration
1860-2000 : Measured
2000-2100 : IPCC A2 scenario
Atmospheric
model (LMDZ)
A2 scenario : PCO2 reaches 850
ppm in 2100
Land surface
Model
(ORCHIDEE)
Coupler
(OASIS)
Ocean General
circulation Model
(OPA)
• Temperature
• Currents
• Productivity
• Dissolved Oxygen
• pH
Ocean
Biogeochemical
(NPZD) Model
Sea-ice
model (LIM)
Projected differences (°C)
2035-2000 (A2 scenario)
+ 0.5 / 1.5°C
Temperature
Species
Skipjack
Yellowfin
Bigeye
Albacore
Southern
bluefin
Abundant
occurrences (°C)
20-29
20-30
13-27
15-21
17-20
Range of sea surface temperature
where substantial commercial catches
are made (source: Sund et al., 1981).
2100-2000 (A2 scenario)
Development of tuna fisheries
took place in a
warming ocean
+ 1.5 / 3.0°C
IPCC (2007). Time series of
global annual ocean heat
content for the 0 to 700 m
layer (observations).
Projected differences (micromole/L)
2100-2000 (A2 scenario)
Oxygen
Species
5m
Skipjack
decrease in
surface
Yellowfin
Bigeye
Albacore
Fork length Lower lethal O2
(cm)
levels (ml l-1)
50
1.87
Less tolerant
to low values
75
2.16
50
1.14
75
1.77
Most tolerant
50
0.40
to low values
75
0.50
50
1.23
75
1.03
… Standard hypothesis that phytoplankton
growth uses constant C/N ratio
100m
increase in
subsurface??
But…
increasing pCO2
could lead to changes
of C/N ratio (Oschlies
et al. 2008)…
In that case the
result is quite
different!
simulations from IPSL-CM4 global climate model.
NPP Projected change (%)
2035-2000 (A2 scenario)
Ocean Productivity
zooplankton
Behrendfeld et al 2006. SeaWifs
satellite based net primary production
micronekton
2100-2000 (A2 scenario)
decrease
Credit:Rudy Kloser and Jock
Young CSIRO, Australia
Tuna larvae
Summary of expected impacts
Observed effects of climate variability on tuna with ENSO
• Large-scale east-west displacements of skipjack in the Pacific are correlated with ENSO events.
• These displacements lead to large fluctuations in catches from the EEZs of PICTs.
• There is evidence that recruitment of tuna is influenced strongly by variability in ENSO.
Vulnerability of oceanic fisheries to the effects of climate change
Ocean temperature
• Projected changes should affect distribution of tuna by changing spawning location / success and
accessibility to forage
• Good fishing grounds could be displaced further eastward or shift to higher latitudes.
Dissolved oxygen
• Projected changes in O2 should have limited impact on tuna in WCPO (large uncertainty in the east)
Ocean currents
• Impact on the dispersal (and mortality) of larvae and juveniles,
• Effect on the distribution of prey for adults.
Ocean acidification
• Unknown. lower rates of growth and egg production? Noisier environment.
Productivity and food web
• Projected decrease in productivity of the food web, thus less prey for larvae and adults
• Adults are highly mobile and can move to more favorable (new) foraging grounds.
Integrated approach
Modeling the interaction of oceanic variables with tuna
biology and population dynamics
SEAPODYM: Spatial Ecosystem And Populations Dynamics Model
Movement toward
feeding grounds
Feeding Habitat =
Food abundance x
accessibility (T,DO)
Mortality
Age-structured
Population
Growth
mortality
IF MATURE
Seasonal
switch
by cohort
Spawning success
Recruitment
Movement toward
spawning grounds
Spawning Habitat =
Food & T for larvae
Absence of adults’preys
Integrated approach
1- Predict observed
variability
Currents
Food (mnecton)
Dissolved O2
Movement toward
Feeding Habitat =
feeding grounds
Food abundance x
accessibility (T,DO)
Temperature
Mortality
Age-structured
Population
Growth
mortality
IF MATURE
Seasonal
switch
by cohort
Spawning success
Recrutement
Movement toward
2 – Project Climate
Change impact
spawning grounds
pH
Spawning Habitat =
Food & T for larvae
Absence of adults’preys
Primary
Production
Integrated approach
Bigeye
Adults biomass
Larvae density
Skipjack
2000
2000
2050
2050
2000
2000
2050
2050
Projected changes in the biomass (tonnes) and
abundance of adult skipjack and bigeye tuna under
the A2 emissions scenario . Simulations are based
on average fishing effort for the period 1980-2000.
Projected change in tuna production
SEAPODYM projected percentage changes in catches of
skipjack and bigeye tuna, relative to recent catches (20year average 1980-2000)
Projected fishing effort = average 1980-2000
Skipjack tuna
Estimated catch increases across the region until 2035
Greater increases for PICTs in the eastern than in the
western Pacific.
After 2050, the biomass of adults decreases significantly in
the WCPO (-32% in 2100 under the A2 scenario) due to
projected major changes in temperature, and productivity at
lower and mid trophic levels. This result is of lower
confidence due to the uncertainty of projected changes
from climate and biogeochemical models.
Bigeye tuna
No obvious difference in the projected distribution and
biomass of adult bigeye until 2035.
In the 2nd half of Century, the western equatorial Pacific is
predicted to become less favorable for spawning. But
increase in survival of larvae in subtropical regions.
An increasing mortality and eastward movement of older
stages is predicted due to poorer habitat. This projection
has a lower confidence due to uncertainty on projection of
dissolved oxygen
Skipjack
PICT
Melanesia
Fiji
New Caledonia
PNG
Solomon Islands
Vanuatu
Micronesia
FSM
Guam
Kiribati
Marshall Islands
Nauru
CNMI
Palau
Polynesia
Am. Samoa
Cook Islands
Fr Polynesia
Niue
Pitcairn Islands
Samoa
Tokelau
Tonga
Tuvalu
Wallis & Futuna
B1/A2
2035
B1
2100*
Bigeye
A2
2100
B1/A2
2035
B1
2100
A2
2100
25.8
22.5
3.1
3.2
18.4
24.0
18.7
-10.6
-5.5
15.1
33.1
39.4
-30.2
-15.4
26.1
0.8
1.1
-4.5
0.1
-3
0.7
1.2
-13
-2.9
-6.1
-1.4
6
-27.9
-7.3
-9.7
14.0
15.8
36.8
24.0
25.1
23.0
10.2
4.8
10.5
43.1
24.2
19.7
21.7
1.7
-15.8
-7.7
24.1
9.8
-1.2
13.2
-26.9
-3.5
-6.7
-0.7
-3.1
-1.4
-0.3
-3.9
-11.5
-12.7
-5.4
-9.6
-6.6
-4.9
-11.2
-32.5
-32.7
-16.6
-26.9
-19.5
-22.6
-45.2
41.1
40.4
40.8
57.8
47.4
76.9
44.0
60.8
47.0
36.8
44.2
47.8
50.2
48.9
nea
nea
49.2
69.0
50.2
40.9
48.7
54.9
63.2
58.5
25.0
46.4
-4.7
-3
-1.6
-5.4
-2.3
1.4
-3.1
-4
2.9
0.4
-7.9
-7.8
-7.7
-7.8
-4.5
1.4
-6.5
-5.1
2.2
-0.4
-17.9
-15.5
-12.5
-14.7
-4.1
-4.2
-16.1
-10.3
-6.2
-6.9
18.9
10.7
36.9
12.4
-0.2
43.2
-7.5
-21.5
26.8
0.33
-2.03
3.3
-8.8
-12.3
-4.5
-26.7
-33.8
-17.8
REGIONAL
Total fishery
Western fishery**
Eastern fishery***
Management recommendations for adaptation
The overall management framework (WCPFC, FFA, the PNA and Te Vaka
Moana groups) and all PICTs fishing authorities should explicitly consider
the implications of climate change when developing management
objectives and strategies over the coming years.
According to projections for the 21st century, the boundary between the
WCPFC convention area and the Inter-American Tropical Tuna Commission
(IATTC) at 150⁰W would no longer be meaningful. Close cooperation
(merging?) between the two commissions is highly necessary.
It is a very high priority to maintain the bigeye tuna stock in the WCPO
in a healthy state to avoid unfavorable combination of high fishing
pressure and adverse environmental conditions in the coming decades.
Effective conservation measures need to be implemented quickly because
simulations show that it takes at least two decades for the WCPO bigeye
stock to fully benefit from a reduction in fishing effort.
Management recommendations for adaptation
PICTs and particularly the PNA need to further develop their
management systems to ensure flexibility to cope with a potentially
changing spatial distribution of the fishing effort.
The transferability aspect of the PNA vessel days scheme (VDS) that
allocates fishing effort among the EEZs according to agreed criteria will
need to be implemented and adjusted in the future according to changing
distributions
Future socio-economic scenarios likely to drive future fishing effort in the
region need to be developed.
Management recommendations for adaptation
Spatially-explicit management in archipelagic areas, currently beyond the
mandate of WCPFC, are needed to monitor and assess potential subregional effects, e.g., increase of productivity due to projected increases in
rainfall and run-off of the Sepik-Ramu and other large river systems.
Skipjack reanalysis at 2°x month
IPCC forcing (2°x month)
1 yr
average
1 yr
average
?
Skipjack reanalysis at ¼° x week
•New IPCC AR5 simulations
•Downscaling techniques

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