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Teasing out the impacts of climate change on fisheries in the Lower Mekong Basin

Ian G. Cowx

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FISHADAPT Bangkok, 8 August 2016

UNIVERSITY OF

Hull International Fisheries Institute

HIFI

Outline

• Importance of Mekong Fisheries

• Drivers of fisheries production

• Climate change scenarios• Impact of other

anthropogenic pressures on fisheries LMB

• Adaptation strategies

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Fisheries of the lower Mekong BasinTotal first-sale value is US$7.0

billion per year

• Per capita consumption average is about 46 kg/person/year

200+ species; 30+ of high commercial importance

More than 50% of total fish catch in the lower Mekong basin (about 1.3 million tonnes worth US$2.5 billion) dependent on migratory fish

Fish production dependent on fish migration (all seasons of year)and extent of flooding

Link between fisheries and hydrological cycle

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01-M

ay

29-M

ay

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Wat

er d

ischa

rge

(m3 /

s)

Day-month

High flow nursing and feedingin the floodplain

Minimum flow refuge in dry season habitat (deep pool)

Medium flow moving from mainstream to tributary

Extreme flow spawning in the floodplain

Medium flow migrating from floodplain to mainstream for dry season refuge

Extreme flowSpawning on the floodplain

High flowNursery and feeding on the floodplain

Medium flowMigrating from floodplain to mainstream for dry season refuge

Minimum flowRefuge in dry season habitats (deep pools)

Medium flowMigrating from mainstream for to tributaries

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Drivers of fish productionWater level and flooding• Water level and extent of

flooding key drivers of fish production

• Shifts in fisheries productivity due to changes in hydrological patterns

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120000

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Capt

ure

fish

yiel

d (t)

Mea

n an

nual

wat

er le

vel (

m)

meanannual

Annual Delta fishery

Annual Tonle Sap

y = 47575x - 15010R² = 0.5366

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Catc

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Catch rateWater Level

Daily catch driven by water level in delta

Climate change scenarios

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Climate changePredicted effects of climate change in Lower Mekong Basin

Temperature Precipitation

Predicted shift in daily discharge at Kratie

Climate change - hydrologyAlteration of flood cycleo Potential greater rainfall

in monsoon season in Viet Nam Highlands altering flooding magnitude, duration and extent in LMB

o More extreme flooding cycle.

o 3-10% increase in wet season flows

o 2-6% reduction in dry season flows

Total average daily discharges simulated by VIC model for Mekong at Kratie for baseline period (1995-2004) and future decades

Source: TKK & SEA START RC 2009 [http://users.tkk.fi/u/mkummu/water&cc]

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Predicted change in fish yield (t)

Mekong delta + 65,000Cambodian floodplain

+ 44,300

Tonle Sap + 30,200Total change + 139,500

Climate change – fish productionPredicted shift in daily discharge at Prek Kdam---- baseline---- Climate change scenario

= +10% increase in fish production

2015 El Niño

Severe reduction in flood peak and durationTonle Sap dai fishery closed early in November (2015) rather than February/March

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Wat

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vel (

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Annual water level in Tonle Sap, Cambodia –red indicates current el Niño year

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Other external pressures on Mekong fish and fisheries

Intense fishing pressure Phnom Penh

Agricultural development -rice fields- fertilsers- pesticides

Alien species from aquaculture

40.02

17.4410.27

17.08

13.06 2.10whitefish

grey fish

black fish

marine/estuarine

exotics

OAAs

MiningFlood

mitigation measures

Rubber plantation

Sediment extraction

Major threats to inland fisheries

Pollution

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Xayaburi(2012)

Don Sahong(2014)

9 planned dams on LMB (mainstream) – two under construction.

23 existed dams (> 20 MW) on tributaries

Many more tributary dams are projected or under construction

Hydropower dams

Floodplain & basin connectivity

It isn’t just about damming rivers......!

• Every dot is a registered water control structure

• Loss of connectivity = loss of productivity in floodplain/riverine fisheries

The MRC water structures map

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Impact on Fisheries - hydropower• Flows similar to current situation =

marginal loss of fish production

• Possible impact of onset and offset and duration of flood pulse on fisheries

• No significant changes in wetted areas of different habitat types

• Biggest impact barrier effect of dams disrupting migration pathways

• 70% reduction is sediment delivery to delta

Impact on Fisheries - hydropower

Indicator/Sub-indicator Vietnam CambodiaBaseline Fisheries yield1 (t) 692,118 481,537Baseline OAA yield1 (t) 160,705 105,467Loss of fish due to reduced habitat flooding (t) 1172 52

Loss of OAAs due to reduced habitat flooding (t) 272 11Loss due barrier effects of dams (t) [primarily white fish] 221,478-

276,847142,535,-

178,169Loss of fish due to reduction in sediment loading andnutrients

96,095-121,393

80,240-97,031

Loss of OAAs due to reduction in sediment loading andnutrients

222,747 21,012

Cumulative loss of fish adjusting for 100% whitefish lossdue to barrier effects (t)

344,043-374,114

236,618-258,460

Cumulative loss of OAAs (t) 23,019 21,023Total loss of capture fishery and OAA yield 367,062-

397,133260,642-279,483

Bottom line: 49.7 and 54% of fish will be lost in the Cambodian

floodplain and Vietnamese delta

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Isolation of floodplain by dykes to intensify rice production –3 crops per year

Impact on fisheries - rice production

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4,50019

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Ric

e fa

rmin

g ar

ea (

thou

sand

Ha) 1.785 million ha

Rice farming areas (more crops): --> habitat degradation

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Ric

e p

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(th

. to

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Inla

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ctio

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ton

s)

Inland capture production (ton) Rice production (thousand tons)

Based on household surveys following hydropower development:

• Shift in livelihoods of fishing communities towards employment such as construction [but not agriculture]

•Shift is diets: Fish and OAAs contribute about 70% of animal protein intake but drops to 54% and replaced by beef

• Fish farming not adopted because of high capital and operating costs

Adaptation strategies

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• Overriding influence on the capture fisheries of the Lower Mekong Basin will be the development of dams for hydropower

• Better understand links between hydrological and nutrient dynamics and fisheries production to improve Climate change impact assessment

• Better understand adaptation strategies of local fishing communities to climate change and other environmental degradation.

• Fisheries overlooked in policy framework: need to improve mechanisms to communicate importance of fisheries to livelihoods, local economies and food security and influence decision making – use ecosystem services approach

CONCLUSIONS