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Projected changes to coastal fisheries

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Presentation on theme: "Projected changes to coastal fisheries"— Presentation transcript:

1 Projected changes to coastal fisheries

2 Based on......

3 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

4 Coastal fisheries catch – Cook Islands
Commercial Subsistence Source: Gillett (2006)

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

6 Demersal fish Solomons – spearing, netting, line fishing targeting snapper, groupers, coral trout

7 Nearshore pelagic fish
Solomons – YF and skipjack tuna, Spanish mackerel (king fish), rainbow runner, mahi mahi and bait fish for pole and line tuna fishery (small pelagics – booma and roma)

8 Invertebrates Solomons – beche de mer, trochus, spiney lobster, mud carb, giant clams (food), whelks, oysters

9 Coastal fisheries catches – Cook Islands
14 t/yr 146 t/yr 240 t/yr Pratchett et al. 2011

10 Demersal fish catch composition
Availability Catch Percentage Pratchett et al. 2011

11 Indirect effects of climate change
% Coral cover Area (km2)

12

13 65% decline in abundance and diversity of fishes

14 Effects of habitat degradation
0.5 -0.5 -1 Macroalgae Proportional change Habitat complexity Coral cover Time after extensive coral loss (years)

15 Effects of habitat degradation
50 -50 -100 Macroalgae Percentage change Habitat complexity Coral reef fishes Coral cover Time after extensive coral loss (years)

16 Catch composition Generalists Not vulnerable
Reef associated Vulnerable Coral associated Highly vulnerable

17 Importance of herbivorous fish

18 Herbivorous fish in Cook Islands
Availability Catch Percentage

19 Direct effects of climate change
Temperature pH

20 Effects of temperature
Growth (mg/week) Maximum growth 28-30oC Damsel fish (Acanthochromis polyacanthus) Projected increase 3oC by 2100 Temperature (oC) Zarco Perello and Pratchett 2012

21 Effects of temperature
Fewer & smaller fishes Declines in: growth lifespan reproduction Growth (mg/week) Maximum growth 28-30oC Projected increase 3oC by 2100 Temperature (oC) Zarco Perello and Pratchett 2012

22 Effects of temperature
Normal spawning temperature

23 Effects of ocean acidification
Abalone Byrne 2012

24 Effects of ocean acidification
Munday et al. 2012

25 Projected coastal fisheries production Cook Islands
% catch 2035 2050 2100 Main effects Demersal fish 36 -2 to -5% -20% -20 to -50% Degradation of coral reefs Nearshore pelagic fish* 60 +15 to +20% +20% +10% Changes in distribution of tuna Invertebrates 4 0 to -5 to -10% -10 to Ocean acidification *Based on initial preliminary modelling for skipjack tuna

26 Ciguatera fish poisoning

27 Factors affecting ciguatera
Dead coral & seaweed surfaces Nutrients Water temperature From land-based activities and sewage

28 Priority management measures
Protect structural complexity and biological diversity of coral reefs to sustain fisheries Maintain adequate spawning stocks to help overcome shocks of greater climate extremes Recognise ecological importance of herbivorous fish and ensure stocks are sufficient to maintain ecosystem functions

29 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


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