Projected changes to coastal
fisheries
Based on......
What we will discuss
Projected changes to
atmospheric and oceanic
conditions
Ecosystems supporting fish
Fish stocks/aquaculture species
Implications for economic
development, food security and
livelihoods
Adaptations and policies to reduce
threats and capitalise on
opportunities
Importance of coastal fisheries
Samoa
10000
8600
Production (tonnes)
9000
8000
7000
6000
5000
4000
2540
3000
2000
1000
0
?
1
Aquaculture
10
2
Freshwater
3
Coastal
4
Offshore
Importance of coastal fisheries
is typical of region
Estimated value ($US millions)
300
250
200
150
100
50
0
Commercial and Locally-based
susbsistence
industrial tuna
coastal fisheries
fishing
What are coastal fisheries?
• Demersal fish
• Nearshore pelagics
• Invertebrates
Species not considered
• Deepwater snapper
• Sharks
Demersal fish
Nearshore pelagic fish
Invertebrates
Coastal fisheries - Samoa
1665 t/yr
4420 t/yr
2550 t/yr
Indirect effects of climate change
60
Coral cover (%)
50
40
30
20
Coral cover
10
0
now
2035
2050
2100
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
Others
Caesionidae
Balistidae
Chanidae
Labridae
Kyphosidae
Siganidae
Mullidae
Holocentridae
Scaridae
Mugilidae
Lutjanidae
Carangidae
Acanthuridae
Serranidae
Lethrinidae
Average annual catch (kg/ year)
60000
Catch composition
50000
40000
Generalists
Not vulnerable
30000
20000
10000
Reef associated
Vulnerable
0
Coral associated
Highly vulnerable
Catch composition - Samoa
60,0
50,0
Percentage
40,0
Catch
Species composition
30,0
20,0
10,0
0,0
Source: Pratchett et al. 2011
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
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
34
36
38
Temperature (oC)
Zarco Perello and Pratchett 2012
Effects of temperature
100
Declines in:
growth
lifespan
reproduction
90
80
Growth (mg/week)
70
60
Maximum growth
28-30oC
50
Fewer &
smaller
fishes
40
30
Projected
increase
3oC by 2100
20
10
0
22
24
26
28
30
32
34
36
38
Temperature (oC)
Zarco Perello and Pratchett 2012
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
% larval survival/development
Effects of ocean acidification
Abalone
80
20 deg C
22 deg C
24 deg C
70
60
50
40
30
20
10
0
pH 8.2
pH 7.8
pH 7.6
Byrne 2012
Effects of ocean acidification
Munday et al 2012
Projected coastal fisheries production
Samoa
Fisheries
Demersal fish
Nearshore
pelagic fish
Invertebrates
%
2035
2050
51
-2 to 5%
30
+15 to
+20%
20%
19
0 to 5%
-20%
-5 to
-10%
2100
-20 to 50%
+10%
-10 to 20%
Main effects
Habitat loss
and
degradation
Changes in
distribution of
tuna
Declining
aragonite
saturation
Priority adaptations
1. Protect the structural complexity and biological
diversity of coral reefs, mangroves and sea
grasses to sustain fisheries and maximize
adaptation potential
2. Recognise ecological importance of
herbivorous fishes and ensure their stocks of
are sufficient to maintain ecosystem functions
Priority adaptations
3. Diversify coastal fisheries to target species and
habitats that will be least affected (or favoured)
by climate change
4. Maintain adequate spawning stocks to
overcome the shocks of greater climate extremes
Conclusions
• Coastal fisheries are critically important for both
food security and livelihoods
• Effects of climate change will add to existing
pressures (e.g., overfishing)
• Improved catch data is needed for monitoring
effects of climate change on coastal fisheries
• subsistence fisheries catches
• separate data for each category of coastal
fisheries and species wherever possible