Projected changes to coastal fisheries 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 catch – Cook Islands 133 tonnes per 231year t/yr 220 t/yr 267 tonnes per year 1 2 Commercial Subsistence Source: Gillett (2006) What are coastal fisheries? • Demersal fish • Nearshore pelagics • Invertebrates Species not considered • Deepwater snapper • Sharks Demersal fish Nearshore pelagic fish Invertebrates Coastal fisheries catches – Cook Islands 14 t/yr 146 t/yr 240 t/yr Total catch = 400 tonnes per year Pratchett et al. 2011 Demersal fish catch composition 70.0 60.0 50.0 Availability Catch Percentage 40.0 30.0 Series1 Series2 20.0 10.0 0.0 Pratchett et al. 2011 60 1.2 50 1 40 0.8 30 0.6 20 0.4 10 0.2 0 now 2035 2050 0 2100 Area (km2) % Coral cover Indirect effects of climate change 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 Percentage change 50 0 Habitat complexity -50 Coral reef fishes Coral cover -100 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 Importance of herbivorous fish Herbivorous fish in Cook Islands 70.0 60.0 50.0 Availability Catch Percentage 40.0 30.0 Series1 Series2 20.0 10.0 0.0 4 3.5 3 2.5 2 1.5 Temperature 1 0.5 0 now 2035 8.15 8.1 8.05 8 7.95 pH 7.9 7.85 7.8 2050 2100 Ocean pH Temperature change Direct effects of climate change Effects of temperature 100 90 Growth (mg/week) 80 70 60 Damsel fish Maximum growth 28-30oC 50 (Acanthochromis polyacanthus) 40 30 Projected increase 3oC by 2100 20 10 0 22 24 26 28 30 32 34 36 38 Temperature (oC) Zarco Perello and Pratchett 2012 Effects of temperature 100 Declines in: • growth • lifespan • reproduction 90 Growth (mg/week) 80 70 60 Maximum growth 28-30oC 50 Fewer & smaller fishes 40 30 Projected increase 3oC by 2100 20 10 0 22 24 26 28 30 32 34 36 38 Temperature (oC) Zarco Perello and Pratchett 2012 Normal spawning temperature Effects of temperature 100 90 % Dead fish eggs 80 70 60 50 40 30 20 10 0 27.9 29.5 32.0 32.8 33.9 Temperature (oC) 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 pH 8.2 pH 7.8 pH 7.6 Byrne 2012 Effects of ocean acidification Munday et al. 2012 Projected coastal fisheries production Cook Islands Fisheries Demersal fish % catch 2035 36 -2 to -5% Nearshore pelagic fish* 60 Invertebrates 4 2050 2100 Main effects -20% -20 to -50% Degradation of coral reefs +10% Changes in distribution of tuna -10 to -20% Ocean acidification +15 to +20% +20% 0 to -5% -5 to -10% *Based on initial preliminary modelling for skipjack tuna Ciguatera fish poisoning Factors affecting ciguatera • Dead coral & seaweed surfaces • Nutrients • Water temperature From land-based activities and sewage Priority management measures 1. Protect structural complexity and biological diversity of coral reefs to sustain fisheries 2. Maintain adequate spawning stocks to help overcome shocks of greater climate extremes 3. Recognise ecological importance of herbivorous fish and ensure stocks are sufficient to maintain ecosystem functions Conclusions • Coastal fisheries are important for 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: separate data for each main category of coastal fisheries subsistence fisheries catches