Projected changes to coastal fisheries

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 catch – Cook Islands

231 t/yr220 t/yr 12

133 tonnesper year

267 tonnesper year

CommercialSubsistence

Source: Gillett (2006)

What are coastal fisheries?

• Demersal fish• Nearshore pelagics • Invertebrates

Species not considered • Deepwater snapper• Sharks

Demersal fish

Nearshore pelagic fish

Invertebrates

Total catch = 400 tonnes per year

Coastal fisheries catches – Cook Islands14 t/yr

Pratchett et al. 2011

123

146 t/yr

240 t/yr

Demersal fish catch compositionPe

rcen

tage

Surge

onfish (H

)

Parrotfish

(H)

Snap

pers

Empero

rs

Groupers

Red m

ullets

Squirr

elfish

Rabbitfish

(H)

Drummers

Wrasses

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

Series1Series2

Availability

Catch

Pratchett et al. 2011

Indirect effects of climate change%

Cor

al c

over

now 2035 2050 21000

10

20

30

40

50

60

0

0.2

0.4

0.6

0.8

1

1.2

Area

(km

2 )

65% decline in abundance

and diversity of fishes

Pro

porti

onal

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

Per

cent

age

chan

ge

Time after extensive coral loss (years)

0 1 2 3 4 5 6 7 8 9 10

50

0

-50

-100

Coral reef fishes

Macroalgae

Coral cover

Habitatcomplexity

Effects of habitat degradation

Coral associatedHighly vulnerable

Reef associatedVulnerable

GeneralistsNot vulnerable

Leth

rinid

aeS

erra

nida

eA

cant

hurid

aeC

aran

gida

eLu

tjani

dae

Mug

ilida

eS

carid

aeH

oloc

entri

dae

Mul

lidae

Sig

anid

aeK

ypho

sida

eLa

brid

aeC

hani

dae

Bal

istid

aeC

aesi

onid

aeO

ther

s0

5000

10000

15000

20000

25000

30000

35000

40000

45000

Ave

rage

ann

ual c

atch

(kg/

yea

r)

Catch composition

Importance of herbivorous fish

Herbivorous fish in Cook IslandsPe

rcen

tage

Surge

onfish (H

)

Parrotfish

(H)

Snap

pers

Empero

rs

Groupers

Red m

ullets

Squirr

elfish

Rabbitfish

(H)

Drummers

Wrasses

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

Series1Series2

Availability

Catch

now 2035 2050 21000

0.51

1.52

2.53

3.54

7.87.857.97.9588.058.18.15

Tem

pera

ture

cha

nge

Oce

an p

H

Direct effects of climate change

Temperature pH

22 24 26 28 30 32 34 36 380

10

20

30

40

50

60

70

80

90

Temperature (oC)

Maximum growth28-30oC

Damsel fish(Acanthochromis polyacanthus)

Grow

th (m

g/w

eek)

Projected increase

3oC by 2100

Effects of temperature

Zarco Perello and Pratchett 2012

22 24 26 28 30 32 34 36 380

10

20

30

40

50

60

70

80

90

Temperature (oC)

Maximum growth28-30oC

Grow

th (m

g/w

eek)

Projected increase

3oC by 2100

Effects of temperature

Zarco Perello and Pratchett 2012

Fewer &smaller fishes

Declines in:• growth• lifespan• reproduction

Effects of temperature

27.9 29.5 32.0 32.8 33.9 34.70

10

20

30

40

50

60

70

80

90

100

Temperature (oC)

% D

ead

fish

eggs

Nor

mal

spa

wni

ng te

mpe

ratu

re

Effects of ocean acidificationAbalone

pH 8.2 pH 7.8 pH 7.60

10

20

30

40

50

60

7020 deg C22 deg C24 deg C

% La

rval

surv

ival

Byrne 2012

Effects of ocean acidification

Munday et al. 2012

Projected coastal fisheries productionCook Islands

Fisheries % catch 2035 2050 2100 Main effects

Demersal fish 36 -2 to -5% -20% -20 to

-50%Degradation of coral reefs

Nearshore pelagic fish* 60 +15 to

+20% +20% +10%Changes in distribution of tuna

Invertebrates 4 0 to -5%

-5 to -10%

-10 to -20%

Ocean acidification

*Based on initial preliminary modelling for skipjack tuna

Ciguatera fish poisoning

• Dead coral & seaweed surfaces

• Nutrients

• Water temperature

From land-based activities and sewage

Factors affecting ciguatera

Priority management measures1. Protect structural complexity and biological

diversity of coral reefs to sustain fisheries2. Maintain adequate spawning stocks to help

overcome shocks of greater climate extremes3. Recognise ecological importance of

herbivorous fish and ensure stocks are sufficient to maintain ecosystem functions

Conclusions• Coastal fisheries are important for 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