Projected changes to coastal fisheries Solomon Islands Government

Projected changes to coastal fisheries Solomon Islands Government

Based on. . .

Outline Main components of coastal fisheries Indirect effects of climate change Direct effects of climate change Projected changes to coastal fisheries production • Priority management measures • •

Coastal fisheries – Solomon Islands 3, 250 t/yr Subsistence Commercial 15, 000 t/yr

What are coastal fisheries? • Demersal fish • Nearshore pelagics • Invertebrates Species not considered • Deepwater snapper • Sharks

Demersal fish

Nearshore pelagic fish

Invertebrates

Coastal fisheries – Solomon Islands 3, 575 t/yr 8, 925 t/yr 5, 750 t/yr Total catch = 18, 250 t/yr Gillett 2009

60 600 50 500 40 400 30 300 20 200 Area (km 2) % coral cover Indirect effects of climate change coral cover (%) 10 100 0 now 2035 2050 0 2100 mangrove area (km 2) seagrass area (km 2)

65 % an de d cli di ne ve i rs n a ity b of und fis an he c s e

Effects of habitat degradation Macroalgae Proportional change 0. 5 0 Habitat complexity -0. 5 Coral cover -1 0 1 2 3 4 5 6 7 8 Time after extensive coral loss (years) 9 10

Effects of habitat degradation Macroalgae Proportional change 0. 5 0 Habitat complexity -0. 5 Coral reef fishes Coral cover -1 0 1 2 3 4 5 6 7 8 Time after extensive coral loss (years) 9 10

Others Caesionidae Balistidae Chanidae Labridae Kyphosidae Siganidae Mullidae Holocentridae Scaridae Mugilidae Lutjanidae Carangidae Acanthuridae Serranidae Lethrinidae Average annual catch (kg/ year) 60000 Catch composition 50000 40000 Generalists Not vulnerable 30000 20000 10000 Reef associated Vulnerable 0 Coral associated Highly vulnerable

Percent Catch composition – Solomon Islands Catch Availability

Importance of herbivorous fish

4 3, 5 3 2, 5 2 1, 5 1 0, 5 0 8, 15 8, 1 p. H 8, 05 8 7, 95 7, 9 Temperature now 2035 2050 7, 85 7, 8 2100 Ocean p. H Temperature change Direct effects of climate change

Effects of temperature 100 90 80 Growth (mg/week) 70 60 Acanthochromis polyacanthus Maximum growth 28 -30 o. C 50 40 30 Projected increase 3 o. C by 2100 20 10 0 22 24 26 28 30 32 34 36 38 Temperature (o. C) Zarco Perello and Pratchett 2012

Effects of temperature 100 Declines in: growth lifespan reproduction 90 80 Growth (mg/week) 70 60 Maximum growth 28 -30 o. C 50 Fewer & smaller fishes 40 30 Projected increase 3 o. C by 2100 20 10 0 22 24 26 28 30 32 34 36 38 Temperature (o. C) Zarco Perello and Pratchett 2012

Effects of temperature Normal spawning temperature 100 % Dead fish eggs 90 80 70 60 50 40 30 20 10 0 27, 9 29, 5 32, 0 32, 8 33, 9 Temperature (o. C) 34, 7

Effects of ocean acidification Abalone 80 20 deg C 22 deg C 24 deg C % larval survival 70 60 50 40 30 20 10 0 p. H 8. 2 p. H 7. 8 p. H 7. 6 Byrne 2012

Effects of ocean acidification Munday et al 2012

Projected coastal fisheries production Solomon Islands Fisheries Demersal fish % catch 2035 50 -2 to -5% 2050 2100 Main effects -20% -20 to -50% Habitat loss and degradation Nearshore pelagic fish 31 0% -15 to -20% Changes in distribution of tuna Invertebrates 19 0 to -5% -5 to 10% -10 to -20% Ocean acidification

Priority management measures 1. Protect structural complexity and biological diversity of coral reefs, mangroves and seagrass to sustain fisheries and maximise adaptation potential 2. Recognise ecological importance of herbivorous fish and ensure stocks are sufficient to maintain ecosystem functions 3. Maintain adequate spawning stocks of all species to help overcome the shocks of greater climate extremes

Conclusions • Coastal fisheries are critically important for both food security and livelihoods • Effects of climate change will add to existing pressures (e. g. overfishing) • Improved catch data are needed for monitoring effects of climate change on coastal fisheries: Ø separate data for each main category of coastal fisheries Ø subsistence fisheries catches

Thank you j. johnson@c 2 o. net. au