Presented byPeter Gehrke

Projected changes to freshwater fish stocks

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 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

Flow – the Maestro

Effects of altered rainfallFreshwater 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 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%

Likelihood

Confidence

Effects on fisheries

Projected fisheries changes

PICT Production (tonnes)

Average projected change (%)

2035 2050 2100Melanesia

Fiji 4,146 0 0 12.5(5 – 20)

Papua New Guinea 17,500 2.5 7.5 7.5Solomon Islands 2,000 2.5 7.5 7.5

Vanuatu 80 2.5 0 7.5Polynesia

French Polynesia 100 2.5 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.