Projected changes to coastal fisheries
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Transcript of Projected changes to coastal fisheries
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