Projected changes to freshwater fish stocks Presented by

Projected changes to freshwater fish stocks Presented by Peter Gehrke

Key messages • Freshwater fisheries are important in Fiji!!! • Increased rainfall will increase freshwater habitats in tropical regions, less in subtropics • Freshwater fish production increase by 5 – 20% • Disturbed catchments restrict production • Five adaptations to maximise positive outcomes and minimise negative effects

Freshwater fisheries in Fiji • Fijian catch > 4, 000 t/y, total 24, 000 t/y • 3% of wild catch value • Dominated by invertebrates • Subsistence and commercial value • Part of culture and language

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 El Niño +8 +20 – 30 +18 – 38 +70 – 110 +23 – 51 +90 – 140 Increased intensity Continuing feature but frequency & intensity uncertain

Flow – the Maestro

Effects of altered rainfall Freshwater fish catches typically correlated to river flows

Temperature • Sex ratios • Growth rates • Larvae feed earlier (starvation? ) • Muscle development • Pollutants increase sensitivity (lower temp tolerance)

Sea level Barriers (waterfalls, weirs, culverts) may block retreat of freshwater fish and clams

Projected habitat changes PICT Lower 2035 Upper Lower 2050 Upper Lower 2100 Upper Melanesia Fiji -5% 5% 5% 20% PNG -5% 5 -10% -5% 20% Solomon Islands -5% 5 -10% -5% 20% 5% 10% Vanuatu -5% 5 -10% -5% 5% 5% 10% -5% 10% -10% >20% Polynesia French Polynesia Likelihood Confidence

Effects on fisheries

Projected fisheries changes PICT Production (tonnes) Average projected change (%) 2035 2050 2100 Melanesia Fiji 4, 146 0 0 Papua New Guinea Solomon Islands Vanuatu Polynesia French Polynesia 17, 500 2, 000 80 2. 5 7. 5 0 12. 5 (5 – 20) 7. 5 100 2. 5 7. 5

Adaptation recommendations 1. Improve habitat management to reduce exposure and sensitivity to climate change

Adaptation recommendations 2. Build capacity of local communities to manage habitats and fisheries resources

Adaptation recommendations 3. Adopt more efficient fishing methods and limit fishing effort

Adaptation recommendations 4. Manage threats from invasive species

Adaptation recommendations 5. Monitor catches and measure the success of management interventions

In summary … The outcomes of climate change for Fiji’s freshwater fisheries will be determined by the effectiveness of strategies to minimise human impacts at the catchment scale.