Projected changes to freshwater fish habitats and stocks
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Projected changes to freshwater fish habitats and stocks
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Based on.......
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Outline
•Importance of flow
•Connectivity of freshwater habitats
•Effects of climate change on:
habitats
fisheries production
•Importance of catchment management
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Freshwater fisheries in the region
•Catch 24,000 tonnes per year
•4% of GDP derived from fisheries
Photo Jacob Wani
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Diversity of freshwater habitats
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Flow – the Maestro
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Flow responses to rainfall
Daily flow, Nabukavesi Creek, Fiji
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Range of freshwater habitats
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Fish migration and habitat connectivity
Source: Gehrke et al 2011
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Climate change effects
Climate feature 2035 2050 2100
Air Temperature (˚C) +0.5 – 1.0 +1.0 – 1.5 +2.5 – 3.0
Rainfall (river flow)
+5% - 20% in equatorial
regions
+10% - 20% in equatorial
regions
5% - 20% decrease in subtropics
Extremes (wet years, dry years) become more extreme
Sea level (cm)(salinisation)
+8+20 – 30
+18 – 38 +70 – 110
+23 – 51 +90 – 140
Cyclones Increased intensity
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Effects on freshwater are different!
•Climate change will affect the quantity of freshwater habitat available to fisheries
•Changes in water quality and habitat quality will be secondary to changes in flow
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Effects of altered rainfall•C
limate change will affect the quantity of freshwater habitat available to fisheries
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Temperature and CO2
• Increasing CO2 will promote growth of aquatic and riparian vegetation
Photo: David Boseto
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Sea level
•Barriers (waterfalls, weirs, culverts) may block retreat of freshwater habitats
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Projected habitat changes
PICT 2035Lower Upper
2050Lower Upper
Melanesia
Fiji -5% 5% -5% 5%
PNG -5% 5-10% -5% 20%
Solomon Islands -5% 5-10% -5% 20%
Vanuatu -5% 5-10% -5% 5%
Polynesia
French Polynesia -5% 10% -5% 10%
Samoa -5% 10% -5% 10%
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Interactions in disturbed catchments
Source: Google Earth
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Effects on fisheries
Photo: Erin Michelle Smith
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Projected fisheries changes
PICT Production (tonnes)
Average projected change (%)2035 2050 2100
MelanesiaFiji 4,146 0 0 12.5Papua New Guinea 17,500 2.5 7.5 7.5Solomon Islands 2,000 2.5 7.5 7.5Vanuatu 80 2.5 0 7.5PolynesiaFrench Polynesia 100 2.5 2.5 7.5Samoa 10 2.5 2.5 7.5
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Adaptation recommendations
Photo: Joanna Ellison
•Maintain vegetation in catchments to avoid sediments and nutrients entering waterways
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Management recommendations•B
uild capacity of local communities to manage habitats and fisheries resources
Photo: Joanna Ellison
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Management recommendations
•Adopt more efficient fishing methods and limit fishing effort
Photo: Boga FigaPhoto: Boga Figa
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Adaptation recommendations
•Manage threats from invasive species
Photo: Boga Figa
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Adaptation recommendations
• Monitor catches and measure the success of management interventions
Photo: Jacob Wani
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Putting climate change in perspective‘
In tropical systems it is possible that the effects of global climate change will be overshadowed by other, larger disturbances such as deforestation and land-use changes.’ (Ficke et al. 2007)
Photo: Jacob Wani
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Summary
•Increased rainfall will increase freshwater habitats in tropical regions
•Freshwater fish production may increase by 5-10%
•Disturbed catchments restrict production
•Ridge to reef management is needed to maximise positive outcomes and minimise negative effects