Projected changes to coastal fisheries
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Projected changes to coastal fisheries
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Based on......
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What we will discussProjected 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
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Importance of coastal fisheriesSamoa
Aquaculture Freshwater Coastal Offshore
Prod
uctio
n (t
onne
s)
? 10
8600
2540
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Importance of coastal fisheriesis typical of region
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What are coastal fisheries?
• Demersal fish• Nearshore pelagics • Invertebrates
Species not considered • Deepwater snapper• Sharks
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Demersal fish
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Nearshore pelagic fish
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Invertebrates
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Coastal fisheries - Samoa
4420 t/yr2550 t/yr
1665 t/yr
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Indirect effects of climate change
Coral cover
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65% decline in abundance
and diversity of fishes
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Pro
port
iona
l cha
nge
Time after extensive coral loss (years)
0 1 2 3 4 5 6 7 8 9 10
0.5
0
-0.5
-1
Macroalgae
Coral cover
Habitatcomplexity
Effects of habitat degradation
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Pro
port
iona
l cha
nge
Time after extensive coral loss (years)
0 1 2 3 4 5 6 7 8 9 10
0.5
0
-0.5
-1
Coral reef fishes
Macroalgae
Coral cover
Habitatcomplexity
Effects of habitat degradation
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Coral associatedHighly vulnerable
Reef associatedVulnerable
GeneralistsNot vulnerable
Catch composition
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Catch composition - SamoaP
erce
ntag
e
Source: Pratchett et al. 2011
CatchSpecies composition
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Direct effects of climate change
Temperature
pH
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Temperature (oC)Temperature (oC)
Maximum growth28-30oC
Acanthochromis polyacanthus
Projected Projected increaseincrease
33ooC by 2100C by 2100
Effects of temperature
Zarco Perello and Pratchett 2012
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Maximum growth28-30oC
Effects of temperature
Fewer &smaller fishes
Declines in: growth lifespan reproduction
Projected Projected increaseincrease
33ooC by 2100C by 2100
Temperature (oC)Temperature (oC)
Zarco Perello and Pratchett 2012
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Effects of temperature
Nor
mal
spa
wni
ng t
empe
ratu
re
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Effects of ocean acidificationAbalone
Byrne 2012
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Effects of ocean acidification
Munday et al 2012
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Projected coastal fisheries productionSamoa
Fisheries % 2035 2050 2100 Main effects
Demersal fish 51 -2 to -5% -20% -20 to -
50%
Habitat loss and
degradation
Nearshore pelagic fish 30 +15 to
20% +20% +10%Changes in
distribution of tuna
Invertebrates 19 0 to -5%
-5 to -10%
-10 to -20%
Declining aragonite saturation
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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
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Priority adaptations3. 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
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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