Impacts of mainstream dams on fisheries andmitigation options Current status of knowledge

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Impacts of mainstream dams on fisheries
and mitigation options - Current status of
knowledge

• Chris Barlow
• Fisheries Programme
• Mekong River Commission

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Three parts to this presentation

• Mekong fisheries, migration, and dams
• Mitigation conclusions from existing knowledge
• Mitigation technologies in other countries

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The Mekong has the worlds largest inland
fishery1.5-3 million tonnes per annum
(calculation in 2000 was 2.6 million tonnes)
Lower Mekong 1-1.3million tonnes
Middle Mekong 0.9-1.2 million tonnes
Upper Mekong 60,000 tonnes
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Mekong fisheries are valuable

• Economic value
• Estimated at US 2-3,000 million per annum
• Employment and Income
• Tonle Sap - 80 of people fish
• Lao PDR gt 50 fish 80 in south (20 household
  income)
• Nutrition
• Fish main source of animal protein (49-82),
  Vit A and calcium
• Per capita consumption 29-39 kg fish flesh p.a.

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Migration is a key feature of the life history of
many Mekong species
Between 40-70 of total fish catch in the lower
Mekong basin is dependent on long distance
migrants (upper end, gt 1.3 million tonnes worth
gtUS2 billion)
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Mitigation conclusions from existing knowledge

• 1. Dams are a barrier to fish migration
• More fish downstream and in bigger rivers
• 3. Therefore dams located downstream have greater
  impact on fisheries production than dams located
  upstream

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Mitigation conclusions from existing knowledge

• Existing technology for fish passages cannot cope
  with high biomass and species biodiversity as
  found in the lower Mekong
• North America and Europe 5-8 species
  (Salmonids)strong upstream swimmers, defined
  seasonal migrations
• Mekong approx. 50 species and 100x
  biomassmigration of different species all year

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Mitigation conclusions from existing knowledge
Fish movement at Khone Falls from Baran 2006
Fish migration triggers in the LMB and other
tropical freshwater systems
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Mitigation learning from technologies in other
countries
Columbia River, USA
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Mitigation fish ladder low dams only
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Mitigation rock-ramp fishway low dams
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Mitigation fish lock low-medium dams
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Mitigation fish lift or elevator potentially
high dams
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Mitigation nature-like bypass
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Mitigation combination Itaipu dam in Sth
America
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Mitigation learning from technologies in other
countries

• Fish ladders, passage, upstream and downstream
• Upstream - Fish ladders for low dams (lt6-10 m)
  fish locks and lifts for higher dams but
  technology is in its infancy
• Downstream - Number of species high biological
  information low
• target species or
• multiple strategies high flow volumes
  by-passing turbines multiple routes
• Tailor to fish species, location, dam design and
  turbine typeUnderstand fish biology, especially
  behaviour
• Integrate mitigation and flexibility into dam
  design at start

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Mitigation learning from technologies in other
countries

• Reservoir fisheries
• Reservoir fisheries generally do not compensate
  for lost river fisheries
• Aquaculture
• Aquaculture not a full replacement for capture
  fishery (added costs, different beneficiaries)

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Mitigation learning from experience in other
countries

• Lessons from the Columbia River
• Dams now managed for fish 1st priority -
  electricity 2nd priority
• Williams 2008 review over last 30 years gtUS7
  billion on mitigation (200-300 million per
  year)- result stopped species becoming
  extinct, but not saved biomass, which is now lt25
  historical fishery
• Lessons from Fraser River
• Decision 1950-60s not to put dams on mainstream-
  result comparatively healthy fish stocks (gt50
  historical fishery)
• Lessons from Parana River fish elevators
• Passed 10,000 fish per day but this is only 2
  of migratory fish biomass(Tonle Sap peak
  migration 50,000 fish per minute!)

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Summary

• Mekong fisheries - critically important
  (nutrition economy)
• 40-70 of benefit (gtUS2 billion) - dependent on
  mainstream migration
• Dams - block migration ? reduce production ?
  economic loss social deprivation
• Current knowledge
• existing mitigation technologies cannot handle
  scale of Mekong migration (6-10x species and 100x
  biomass), nor high dams
• dams upstream and in tributaries have
  comparatively less impact than dams downstream
• Can use existing concepts but need to adapt for
  every dam
• If dams built incorporate mitigation and
  flexibility from start

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Some on-going MRC Fisheries Programme work

• Improving understanding- modelling impacts of
  dams on mainstream- defining important spawning
  sites on mainstream- reviewing reservoir
  fisheries- guidelines for impact assessment and
  forecasting- options for mitigation- assessing
  socio-economic impact of reduction of migratory
  fish yield
• Expert group for fish passage- available for
  advice on Mekong issues biologists and
  engineers
• Briefing governments, planners and developers

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Thank you