Fisheries Myths. Ray Hilborn School of Aquatic and Fishery Sciences University of Washington

Transcription

1 Fisheries Myths Ray Hilborn School of Aquatic and Fishery Sciences University of Washington

2 Thanks to collaborators

3 Full disclosure of funding

4 Myths to be addressed Stocks worldwide are declining Eating fish is bad for the environment The act of fishing destroys the environment

5 Take away message The status of fish stocks and the sustainability of fisheries is variable some places good, some places bad Fish are generally produced at a much lower environmental cost than alternative forms of protein Bottom trawling impacts are highly concentrated most benthic biota are not particularly impacted some benthic species are very sensitive and those need to be identified and managed

6 The history of Gloom and Doom Science Magazine 1993 Fish stocks are inevitably overexploited before effective management is initiated

7 Global catch MTL Pauly s 1998 Fishing down food webs Pauly et al. (1998)

8 Nature 2003

9 All fish gone by 2048 Science 2006

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11 Source: Time magazine, November 2006

12 What the public believes Stocks worldwide are declining Eating fish is bad for the environment The act of fishing destroys the environment

13 A new consensus on stock status

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15 Most assessed stocks in North America, South America, Europe and Oceania Source: Global Assessment Database (ramlegacy.org)

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17 Are there plenty of fish in the sea? By country Particularly good: US, Iceland, Norway, New Zealand Improving rapidly: European Atlantic Of concern: Japan, Latin America Particularly bad: Mediterranean, NW Africa Unknown but probably bad: Most of S and SE Asia

18 Looking at 75% of the stocks

19 Abundance of harvested species

20 All stocks

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22 Were the Prophets of Doom correct? Ludwig Hilborn and Walters 1993 For much of the world yes, overexploitation was the norm before management was imposed BUT there were exceptions, New Zealand and Alaska stand out as regions that absorbed the lessons of the rest of the world, and because they developed industrial fishing much later avoided any systematic overfishing

23 Global catch MTL Fishing down food webs Current data Pauly et al. (1998) Branch et al. (2010) Nature 468:

24 Demise of world tuna stocks From Juan-Jorda et al PNAS.

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26 Past icons of fisheries failure that are now success stories Patagonia toothfish MSC certified Orange rough in New Zealand recommended for MSC certification Atlantic bluefin tuna - rapidly rebuilding

27 What the public believes At least Daily Star readers Experts have warned that cod are all but extinct

28 North Atlantic Cod abundance 9,000,000 8,000,000 7,000,000 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000,

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31 Should you eat fish? What is the environmental cost of the alternative?

32 CO 2 per 40 g protein

33 Nutrient release per 40 g protein

34 Imagine you could produce high quality protein Without draining our rivers and aquifers Without polluting rivers with fertilizers Without antibiotics Without causing soil erosion Without chopping down rain forests

35 Organic vegetable field my wife farmed

36 Total loss of native biodiversity in this organic vegetable field

37 My son modifying biodiversity

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39 Trawling footprint is growing

40 Motivation and funding Walton Foundation and Packard Foundation proposed the study in consultation with National Fisheries Institute We assembled the international team Funding for 4 meetings, and 2 post-docs Additional funding from CSIRO (3 year post-doc), NOAA, FAO, ICES and 10 fishing companies.

41 20 million tons of fish caught by trawling An important element in food security, and employment in many countries

42 Phase I Trawl Footprints

43 Collecting the data - Vessel Monitoring System - Logbook data - Effort timeseries

44 High resolution mapping of trawling global footprint

45 High resolution mapping of trawling global footprint

46 High resolution mapping of trawling global footprint

47 High resolution mapping of trawling global footprint

48 Global footprint of trawling

49 Trends in effort

50 What have we learned so far? Trawl effort is highly concentrated with many areas untrawled, some areas have high trawl pressure 90% of effort takes place on small portion of the bottom In fisheries where we have data, trawl effort is declining Scale distorts estimate, fine scale best Footprint is variable among regions

51 Phase II

52 Global distribution of comparative studies Control-Impact Gradient Single commercial trawl event Figure by Jan Hiddink

53 Aggregated effects of different fishing gears across all habitat types. A rank order of impact emerges: 1. Scallop dredging 2. Beam trawling 3. Otter trawling Figure by Jan Hiddink sqrt Relative abundance or biomass Sqrt relative abundance or biomass sqrt Trawling frequency ( y 1 ) Otter trawling OT Beam trawling BT Biogenic Gravel TD Sand Sandy mud & Muddy sand Mud Scallop dredging Sqrt trawling frequency per year

54 Phase III. Net impacts on biota Data sources Trawl Footprint Phase I Mortality from net passage Phase II Recovery time Phase II Habitat maps from DBSeabed Result Depletion of each taxa relative to a no-trawl case

55 Phase III: Net impact on biota

56 Phase IV: ecosystem impacts on target species Evidence that epibenthos is important for some species thus theory that reducing epibenthos reduces production of some species Some experimental evidence that trawling improves productivity of flatfish Areas of most concern are places with lots of epibenthos how much of the bottom has this, what is the strength of impact? No real empirical evidence for population level impact heavily trawled areas continue to produce strong year classes of dependent species

57 Phase V Best Practices Evaluate but not recommend Freeze trawl footprint Prohibition by gear type (e.g. rockhopper gear) Gear modifications Benthic biota by-catch quotas Habitat impact quotas Broad scale habitat management Small scale sensitive habitat protection Rolling hotspots Effort reduction

58 Trawl Conclusions Trawling footprint is highly concentrated with some places intensively fished, many places not fished Most benthic species are not sensitive to occasional trawl contact -- but some are Overall most benthos largely unchanged by trawling Most concern is about the relatively small amount of sensitive species and their habitat

59 Myths Conclusions The status of fish stocks and the sustainability of fisheries is variable some places good, some places bad Most developed countries are stable or increasing Developing countries without effective management systems are where most problems occur Fish are generally produced at a much lower environmental cost than alternative forms of protein Bottom trawling impacts are highly concentrated most benthic biota are not particularly impacted some benthic species are very sensitive and those need to be identified and managed

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