projected changes to coastal fisheries

Projected changes to coastal fisheries

Based on......

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

Importance of coastal fisheriesSamoa

Aquaculture Freshwater Coastal Offshore

Prod

uctio

n (t

onne

s)

? 10

8600

2540

Importance of coastal fisheriesis typical of region

What are coastal fisheries?

• Demersal fish• Nearshore pelagics • Invertebrates

Species not considered • Deepwater snapper• Sharks

Demersal fish

Nearshore pelagic fish

Invertebrates

Coastal fisheries - Samoa

4420 t/yr2550 t/yr

1665 t/yr

Indirect effects of climate change

Coral cover

65% decline in abundance

and diversity of fishes

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

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

Coral associatedHighly vulnerable

Reef associatedVulnerable

GeneralistsNot vulnerable

Catch composition

Catch composition - SamoaP

erce

ntag

e

Source: Pratchett et al. 2011

CatchSpecies composition

Direct effects of climate change

Temperature

pH

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

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

Effects of temperature

Nor

mal

spa

wni

ng t

empe

ratu

re

Effects of ocean acidificationAbalone

Byrne 2012

Effects of ocean acidification

Munday et al 2012

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

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 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

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