Coastal Fisheries: Impacts, Changes, and Management
Explore the dynamics of coastal fisheries, from demersal fish to invertebrates, and learn about the projected changes, direct and indirect effects of climate change, and priority management measures. Discover the catch data from Cook Islands and the implications for sustainable fishing practices.
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Presentation Transcript
Projected changes to coastal fisheries
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 Commercial Subsistence 231 t/yr per year 1 220 t/yr 267 tonnes per year 2 Source: Gillett (2006)
What are coastal fisheries? Demersal fish Nearshore pelagics Invertebrates Species not considered Deepwater snapper Sharks http://www.sciencewithoutborders.org/wp-content/uploads/2012/10/Fig3-trochus-raiatea2_sm-trochus-snail-sm.jpg
Coastal fisheries catches Cook Islands 14 t/yr http://www.sciencewithoutborders.org/wp-content/uploads/2012/10/Fig3-trochus-raiatea2_sm-trochus-snail-sm.jpg 146 t/yr 240 t/yr Total catch = 400 tonnes per year Pratchett et al. 2011
Demersal fish catch composition 70.0 60.0 Availability 50.0 Catch 40.0 Percentage Series1 30.0 Series2 20.0 10.0 0.0 Pratchett et al. 2011
Indirect effects of climate change 60 1.2 50 1 % Coral cover 40 0.8 Area (km2) 30 0.6 20 0.4 10 0.2 0 0 now 2035 2050 2100
Effects of habitat degradation Macroalgae 0.5 Proportional change 0 Habitat complexity -0.5 Coral cover -1 0 1 2 3 4 5 6 7 8 9 10 Time after extensive coral loss (years)
Effects of habitat degradation Macroalgae 50 Percentage change 0 Habitat complexity Coral reef fishes -50 Coral cover -100 0 1 2 3 4 5 6 7 8 9 10 Time after extensive coral loss (years)
Catch composition 60000 50000 Average annual catch (kg/ year) Generalists Not vulnerable 40000 30000 20000 Reef associated Vulnerable 10000 0 Holocentridae Acanthuridae Scaridae Others Mugilidae Lethrinidae Lutjanidae Kyphosidae Labridae Chanidae Siganidae Balistidae Serranidae Carangidae Mullidae Caesionidae Coral associated Highly vulnerable
Herbivorous fish in Cook Islands 70.0 60.0 Availability 50.0 Catch 40.0 Percentage Series1 30.0 Series2 20.0 10.0 0.0
Direct effects of climate change 4 8.15 3.5 8.1 Temperature change 3 8.05 Ocean pH 2.5 8 2 7.95 1.5 pH Temperature 7.9 1 7.85 0.5 0 7.8 now 2035 2050 2100
Effects of temperature 100 90 80 70 Growth (mg/week) Damsel fish (Acanthochromis polyacanthus) Maximum growth 28-30oC 60 50 40 Projected increase 3oC by 2100 30 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 Fewer & smaller fishes 90 80 70 Growth (mg/week) Maximum growth 28-30oC 60 50 40 Projected increase 3oC by 2100 30 20 10 0 22 24 26 28 30 32 34 36 38 Temperature (oC) Zarco Perello and Pratchett 2012
Effects of temperature Normal spawning temperature 100 90 80 % Dead fish eggs 70 60 50 40 30 20 10 0 27.9 29.5 32.0 32.8 33.9 34.7 Temperature (oC)
Effects of ocean acidification Abalone 80 20 deg C 22 deg C 24 deg C 70 60 % Larval survival 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 2035 2050 2100 Main effects catch -2 to -5% -20 to -50% Degradation of coral reefs Demersal fish 36 -20% Changes in distribution of tuna Nearshore pelagic fish* +15 to +20% 60 +20% +10% 0 to -5% -5 to -10% -10 to -20% Ocean acidification Invertebrates 4 *Based on initial preliminary modelling for skipjack tuna
Factors affecting ciguatera Dead coral & seaweed surfaces Nutrients From land-based activities and sewage Water temperature
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
