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Projected changes to freshwater fish habitats and stocks Solomon Islands Government Based on....... Outline • Importance of flow • Connectivity of freshwater habitats • Effects of climate change on: habitats fisheries production • Importance of catchment management Freshwater fisheries in the region • Catch 24,000 tonnes per year • 4% of GDP derived from fisheries Photo Jacob Wani Diversity of freshwater habitats Flow – the Maestro Flow responses to rainfall Daily flow, Nabukavesi Creek, Fiji Range of freshwater habitats Fish migration and habitat connectivity Source: Gehrke et al 2011 Climate change effects Climate feature Air Temperature (˚C) Rainfall (river flow) 2035 2050 2100 +0.5 – 1.0 +1.0 – 1.5 +2.5 – 3.0 +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) Cyclones +8 +20 – 30 +18 – 38 +70 – 110 Increased intensity +23 – 51 +90 – 140 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 • Climate change will affect the quantity of freshwater habitat available to fisheries Temperature and CO2 Photo: David Boseto •Increasing CO2 will promote growth of aquatic and riparian vegetation Sea level •Barriers (waterfalls, weirs, culverts) may block retreat of freshwater habitats Projected habitat changes PICT 2035 Lower 2050 Upper Lower 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% French Polynesia -5% 10% -5% 10% Samoa -5% 10% -5% 10% Polynesia Interactions in disturbed catchments Source: Google Earth Effects on fisheries Photo: Erin Michelle Smith Projected fisheries changes PICT Melanesia Fiji Papua New Guinea Solomon Islands Vanuatu Polynesia French Polynesia Samoa Production (tonnes) Average projected change (%) 2035 2050 2100 4,146 17,500 2,000 80 0 2.5 2.5 2.5 0 7.5 7.5 0 12.5 7.5 7.5 7.5 100 10 2.5 2.5 2.5 2.5 7.5 7.5 Adaptation recommendations • Maintain vegetation in catchments to avoid sediments and nutrients entering waterways Photo: Joanna Ellison Management recommendations • Build capacity of local communities to manage habitats and fisheries resources Photo: Joanna Ellison Management recommendations • Adopt more efficient fishing methods and limit fishing effort Photo: Boga Figa Photo: 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 • 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