Projected changes to coastal
fisheries
Solomon Islands Government
Based on......
Outline
•
•
•
•
Main components of coastal fisheries
Indirect effects of climate change
Direct effects of climate change
Projected changes to coastal fisheries
production
• Priority management measures
Coastal fisheries – Solomon Islands
3,250 t/yr
Subsistence
Commercial
15,000 t/yr
What are coastal fisheries?
• Demersal fish
• Nearshore pelagics
• Invertebrates
Species not considered
• Deepwater snapper
• Sharks
Demersal fish
Nearshore pelagic fish
Invertebrates
Coastal fisheries – Solomon Islands
3,575 t/yr
8,925 t/yr
5,750 t/yr
Total catch = 18,250 t/yr
Gillett 2009
60
600
50
500
40
400
30
300
20
200
Area (km2)
% coral cover
Indirect effects of climate change
coral cover (%)
10
100
0
0
now
2035
2050
2100
mangrove area
(km2)
seagrass area
(km2)
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
Percent
Catch composition – Solomon Islands
Catch
Availability
Importance of herbivorous fish
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
Effects of temperature
100
90
% Dead fish eggs
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
Abalone
80
20 deg C
22 deg C
24 deg C
% larval survival
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
Solomon Islands
%
catch
2035
Demersal fish
Nearshore
pelagic fish
Fisheries
Invertebrates
2050
2100
50
-2 to
-5%
-20%
-20 to
-50%
31
0%
-10%
-15 to
-20%
19
0 to
-5%
-5 to
-10%
-10 to
-20%
Main effects
Habitat loss
and
degradation
Changes in
distribution of
tuna
Ocean
acidification
Priority management measures
1. Protect structural complexity and biological
diversity of coral reefs, mangroves and
seagrass to sustain fisheries and maximise
adaptation potential
2. Recognise ecological importance of
herbivorous fish and ensure stocks are
sufficient to maintain ecosystem functions
3. Maintain adequate spawning stocks of all
species to help 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 are needed for monitoring
effects of climate change on coastal fisheries:
 separate data for each main category of
coastal fisheries
 subsistence fisheries catches
Thank you
j.johnson@c2o.net.au