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Projected changes to freshwater fish habitats and stocks. Based on. Outline. Importance of flow Connectivity of freshwater habitats Effects of climate change Habitats Fisheries production Importance of catchment management. Freshwater fisheries in the region. Catch 24,000 tonnes per year - PowerPoint PPT Presentation
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Projected changes to freshwater fish habitats and stocks
Based on.......
Outline
• Importance of flow• Connectivity of freshwater habitats• Effects of climate change• Habitats• Fisheries production• Importance of catchment management
Freshwater fisheries in the region
• Catch 24,000 tonnes per year
• 4% of GDP derived from fisheries
• Consumption up to 100 kg per year
Photo Jacob Wani
Diversity of freshwater habitats
Flow – the Maestro
Flow responses to rainfallDaily flow, Nabukavesi Creek, Fiji
Seasonal flow, Ba River, Fiji
Episodic flow, Tontouta River, New Caledonia
Range of freshwater habitats
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
El Niño Continuing feature but frequency & intensity uncertain
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
Effects of altered rainfall
Temperature and CO2
• Increasing CO2 will promote growth of aquatic and riparian vegetation
Photo: David Boseto
Sea level
•Barriers (waterfalls, weirs, culverts) may block retreat of freshwater habitats
Projected habitat changes
PICT 2035Lower Upper
2050Lower Upper
2100Lower Upper
Melanesia
Fiji -5% 5% -5% 5% 5% 20%
PNG -5% 5-10% -5% 20% -5% 20%
Solomon Islands -5% 5-10% -5% 20% 5% 10%
Vanuatu -5% 5-10% -5% 5% 5% 10%
Polynesia
French Polynesia -5% 10% -5% 10% -10% >20%
Samoa -5% 10% -5% 10% -10% >20%
Interactions in disturbed catchments
Source: Google Earth
Effects on fisheries
Photo: Erin Michelle Smith
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
Adaptation recommendations
Photo: Joanna Ellison
• Maintain vegetation in catchments to avoid sediments and nutrients entering waterways
Adaptation recommendations• Build capacity of local communities to manage
habitats and fisheries resources
Photo: Joanna Ellison
Adaptation recommendations
• Adopt more efficient fishing methods and limit fishing effort
Photo: Boga FigaPhoto: Boga Figa
Adaptation recommendations
• Manage threats from invasive species
Photo: Boga Figa
Adaptation recommendations
• Monitor catches and measure the success of management interventions
Photo: Jacob Wani
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
Summary
• Increased rainfall will increase freshwater habitats in tropical regions, less in subtropics
• 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