Vulnerability of coastal fisheries
Presented by
Morgan Pratchett
Authors
This presentation is based on Chapter 9 ‘Vulnerability of
coastal fisheries in the tropical Pacific to climate change’
in the book Vulnerability of Tropical Pacific Fisheries and
Aquaculture to Climate Change, edited by JD Bell, JE
Johnson and AJ Hobday and published by SPC in 2011.
The authors of Chapter 9 are: Morgan Pratchett, Philip
Munday, Nicholas Graham, Mecki Kronen, Silvia Pinca,
Kim Friedman, Tom Brewer, Johann Bell, Shaun Wilson,
Joshua Cinner, Jeff Kinch, Rebecca Lawton, Ashley
Williams, Lindsay Chapman, Franck Magron and Arthur
Webb
200000
180000
160000
140000
120000
100000
80000
60000
40000
20000
0
Subsistence
Commercial
300
Total
Estimated value ($US millions)
Annual Production (tonnes)
Coastal Fisheries Production
Gillett 2009
250
200
150
100
50
0
Commercial and Locally-based
susbsistence
industrial tuna
coastal fisheries
fishing
Diversity of coastal fisheries
60000
Annual catch (kg)
50000
40000
30000
20000
10000
0
Distinct fisheries sectors
Demersal fish
Nearshore pelagic fish
Invertebrates
Demersal fish
Nearshore pelagic fish
Invertebrates
4
3.5
3
2.5
2
1.5
1
0.5
0
8.15
8.1
pH
8.05
8
7.95
7.9
7.85
Temperature
now
2035
2050
7.8
2100
Ocean pH
Temperature change
Direct effects of climate change
Indirect effects of climate change
60
1600
Coral cover (%)
Seagrass area
40
1200
1000
30
800
20
600
Coral cover
400
10
200
0
0
now
2035
2050
2100
Areal extent (km2)
1400
50
Effects of temperature
100
90
80
Growth (mg/week)
70
60
Acanthochromis
polyacanthus
Maximum growth
28-30oC
50
40
30
Projected
increase
3oC by 2100
20
10
0
22
24
26
28
30
32
Temperature (oC)
34
36
38
Effects of temperature
100
Declines in:
Fewer &
• growth
smaller
• lifespan
fish
• reproduction
90
80
Growth (mg/week)
70
60
Maximum growth
28-30oC
50
40
30
Projected
increase
3oC by 2100
20
10
0
22
24
26
28
30
32
Temperature (oC)
34
36
38
Normal spawning temperature
Mortality of fertilised embryos (%)
Effects of temperature
100
90
80
70
60
50
40
30
20
10
0
27.9
29.5
32.0
32.8
33.9
Temperature (oC)
34.7
Effects of ocean acidification
Other organisms affected:
• Trochus
• Oysters
• Sea cucumbers
• Crustaceans
• Fish
Source: Fine and Tchernov (2007)
Effects of habitat degradation
Macroalgae
Proportional change
0.5
0
Habitat
complexity
-0.5
Coral cover
-1
0
1
2
3
4
5
6
7
8
Time after extensive coral loss (years)
9
10
Effects of habitat degradation
Macroalgae
Proportional change
0.5
0
Habitat
complexity
-0.5
Coral reef fishes
Coral cover
-1
0
1
2
3
4
5
6
7
8
Time after extensive coral loss (years)
9
10
Projected coastal fisheries production
Projected coastal fisheries production
Fisheries production (tonnes/year)
100,000
90,000
80,000
70,000
60,000
50,000
Demersal fish
Nearshore pelagic fish
Invertebrates
40,000
30,000
20,000
10,000
0
Now
2035
2050
2100
Priority adaptations
• Protect structural complexity and biological
diversity of coral reefs, mangroves and sea
grasses to sustain fisheries and maximize
adaptation potential
• Recognise ecological importance of specific
fish (e.g. herbivorous fish on coral reefs), and
ensure stocks of these species are sufficient
to maintain key ecosystem functions
Priority adaptations
• Diversify coastal fisheries activities to target
species and habitats that will be least
affected, or favoured, by climate change
• Build effects of climate change into fisheries
management, particularly the need to
maintain spawning stocks to overcome
shocks of greater climate extremes
Conclusions
• Coastal fisheries are critically important for
both food security and livelihoods across the
Pacific
• Up until 2035, effects of climate change will
probably be indiscernible against the
backdrop of existing anthropogenic
disturbances, but immediate action is
required to minimize future effects of climate
change on coastal fisheries
Conclusions
• Improved data on catches are needed to
predict and monitor the effects of climate
change on coastal fisheries
Data needed:
 subsistence fisheries catches
 separate data for the 3 distinct fisheries
(or even species)