Fisheries and Global Warming: Impacts on Marine Ecosystems Daniel Pauly Sea Around Us Charles Darwin University Darwin, NT, Australia June 16, 2017
There are two basic modes for fisheries science to be conducted: 1) Tactically, i.e., to answer applied, short-term questions such as what next year s TAC should be; 2) Strategically, i.e., to explore scenarios how the fisheries of, e.g., a given country, should be. The first of these mode concerns over 90% of what fisheries science is (and fisheries scientists do). The second is less familiar; however, if fisheries scientists don t ask strategic questions, who will?
We know that the pressure on the world s fish stocks is increasing relentlessly, notably by the distant-water fleets of a few countries Effective effort (GW or watts x 10 9 ) 9 8 7 6 5 4 3 2 Europe North America 1 Africa, South America Oceania South America 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Asia Anticamara et al. 2011. (Fisheries Research)
The response of these countries to the depletion of their and neighboring waters was to expand the reach of their fisheries. This shows Spain in the 1950s... t/km 2 see www.seaaroundus.org
Now, Spain s fisheries cover the whole world (as do the fisheries of France, Japan, China, etc.) t/km 2 see www.seaaroundus.org
Let s look at the effect of this expansion, combined with the systematic underestimation of fisheries catches. Our example is West Africa, as defined on this map... These are 22 countries, from Morocco in the North to Namibia in the South; the western part of South Africa should also be included.
Total reconstructed catches for West Africa: domestic 4.5 Recreational 4.0 Discards Catch (t x 10 6 ) 3.5 3.0 2.5 2.0 1.5 Subsistence Reported to FAO Sparidae Artisanal 1.0 0.5 Industrial 1 / 2 0.0 1950 1960 1970 1980 1990 2000 2010 Year Belhabib et al. (2016, Environm. Develop.)
The major issue in West African marine fisheries is the pressure exerted by legal and illegal foreign fleets, which prevents the development of national fisheries 10 9 8 7 Discards Reported to FAO Foreign illegal Catch (t x 10 6 ) 6 5 4 Subsistence Foreign legal 1 / 2 3 2 Artisanal 1 Industrial 1 / 4 0 1950 1960 1970 1980 1990 2000 2010 Year Belhabib et al. (2016, Environm. Develop.)
see www.seaaroundus.org
see www.seaaroundus.org
Global catches Pauly and Zeller (2016) Nature Communications 7:10244
When added up, the country catch reconstructions confirm that the world catch has been declining for the last 2 decades. Important is also that the trend is more marked than in the officially reported catch. 1.2 mt/year 0.4 mt/year Pauly and Zeller (2016) Nature Communications 7:10244
Industrial Pauly and Zeller (2016, Nature Communications)
Now recall that ecosystem fluxes move up trophic pyramids 4 3 10% 2 10% 1 *.............. *... *.. *. *.. *... *.. *. *. 10% and each species tends to have its own trophic level
We can thus map the footprint (or seafoodprint ) of fisheries onto the world ocean, here in the 1950s
and in the 2000s. Note that Australia has a relatively small seafoodprint
Let s look at Australia again, which differed from New Zealand already in the 1950s.
and now differs from New Zealand even more, and from other countries in the North as well.
Evolution of the state of marine fishery resources from 1950 to 1994, based on the analysis of catch trends in 200 major stocks (redrawn from Grainger and Garcia 1996, FAO Fish. Tech. Pap.).
We can simplify this, by defining, for catch time series Fully exploited Developing Underdeveloped Over-exploited Crashed Froese and Kesner-Reyes (2002)
A stock-status plot, showing the % of stocks by status. This illustrates the typically increasing number of stocks that are Overfished or Collapsed. Note the new category called Rebuilding. The same, flipped over
Combining the original findings of Grainger and Garcia (1996; black lines) with a flipped-over stock-status plot for global catches (white lines). Note that the trends are very similar. The senescent category of Grainger and Garcia did not account for collapse or rebuilding, which shape the observed trend.
FAO s invention taken over by the Sea Around Us continues to be used by FAO (source: SOFIA 2016)
Do not read it vertically, as when we talk about the percentage of stocks in different categories
Read it semi-horizontally, because the important information is the trend.
Thus, the projection that was rejected by many when it was published in 2006 was very legitimate Stocks (%) 2048?
This rejection was based in part, on a global study fisheries status which was biased toward developed countries Based on an article by Worm, Hilborn et al. (Science, 2009)
And in fact, the critics have come around
This graph, illustrating a Canadian tragedy, leads to several questions. One of them is: why did the stock not rebuild itself since the moratorium declared nearly 25 years ago?
The biomass of cod in Eastern Canada was, in the 2000s, between 10 and 15 times lower than in the 1950s/1960s 5.0 4.5 Biomass (tˑ10 6 ) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 1950 1960 1970 1980 1990 2000 2010 Year
but the exploitation of cod in Eastern Canada continued to be very high, when account is taken of unreported catches. 50% 45% 40% Reconstructed Exploitation rate (%) 35% 30% 25% 20% 15% Reported 29.2% 23.2% 20.4% 10% 12.5% 5% Exploitation rate = ccccccccc bbbbbbbbbbbbbb 0% 1950 1960 1970 1980 1990 2000 2010 Year Average exploitation rate of reconstructed catch Average exploitation rate of reported catch
Lessons from the Northern cod collapse Northern cod did not seem to recover for a long time because overexploitation continued after the moratorium was declared, and even after the fishery was closed ; The mysterious non-recovery of the Northern cod was convenient myth covering for inadequate science and management (notably ignoring small-scale fishers and their catches); The cod is now recovering, and probably, it had been trying to do this all along; and
In the meantime, things are heating up.. Al Gore & IPCC: Nobel Prize 2007
Observed climate-induced shifts in distribution ranges Poleward shifts in distribution ranges of marine species, e.g., in the North Sea (Perry et al. Science, 2005). Cod Angler fish Snake blenny
Simulating poleward shifts using temperature-abundance profiles Small yellow croaker (Larimichthys polyactis) Probability of occurrence by water temperature Relative abundance Low Probability of occurrence 0.20 0.15 0.10 0.05 0.00 2 4 6 8 10 12 14 16 18 20 22 24 26 28 High Temperature (degree C)
Small yellow croaker Year 0
Small yellow croaker Year 2
Small yellow croaker Year 4
Small yellow croaker Year 6
Small yellow croaker Year 8
Small yellow croaker Year 10
Small yellow croaker Year 12
Small yellow croaker Year 14
Small yellow croaker Year 16
Small yellow croaker Year 18
Small yellow croaker Year 20
Small yellow croaker Year 22
Small yellow croaker Year 24
Small yellow croaker Year 26
Small yellow croaker Year 28
Small yellow croaker Year 30
Baldchin groper, Western Australia Year 2001 High abundance Relative abundance Low
Baldchin groper, Western Australia Year 2001 Low High
Baldchin groper, Western Australia Year 2001 Relative abundance Low High
Baldchin groper, Western Australia Year 2010 Relative abundance Low High
Baldchin groper, Western Australia Year 2020 Relative abundance Low High
Baldchin groper, Western Australia Year 2030 Relative abundance Low High
Baldchin groper, Western Australia Year 2040 Relative abundance Low High
Baldchin groper, Western Australia Year 2060 Relative abundance Low High
Cheung, Lam, Kearney, Sarmiento, Watson and Pauly (Fish and Fisheries, 2009)
Projected change in catch potential in 50 years Cheung, Lam, Kearney, Sarmiento, Watson, Zeller and Pauly (Global Change Biology, 2009)
Moreover, we shouldn t forget that global warming already began several decades ago Rate of changes in SST (oc year-1) -0.04-0.02 0 0.02 0.04 0.06 0.08 Ocean warming in the 4 decades from 1970 to 2009 (from Hadley Centre)
And thus we did now what we could have done years ago
We invented a new indicator: the Mean Temperature of Catch (MTC) Median preferred temperature = 8 o C Median preferred temperature = 12 o C Median preferred temperature = 10 o C Median preferred temperature = 6 o C MTC = Average preferred temperature weighted by the catch
Trends in the Mean Temperature of the Catch in two climate types.
Fig 1. Map of the percentage of tropical tuna in longliner catches changes from 1967 2011. Monllor-Hurtado A, Pennino MG, Sanchez-Lizaso JL (2017) Shift in tuna catches due to ocean warming. PLOS ONE 12(6): e0178196. https://doi.org/10.1371/journal.pone.0178196
Why fish shrink when the water gets warm and they can t leave
Predicted changes in assemblage-level maximum body weight by 2050 relative to 2000 Assemblage-averaged W is projected to decrease by 14 24% from 2001 to 2050 (20-year average); Changes in the tropics and temperate regions are predicted to be large, with an average reduction of around 20%. Source: Cheung, Sarmiento, Dunne, et al. (2012) Nature Climate Change
Or, seen from another angle: and there is more
In summary Present trends, if extrapolated, suggest that global fisheries catches will decline further, particularily in the tropics; Some of these trend could be reversed if more countries agreed that stock rebuilding (through restrictive quotas and large marine reserves) is crucial; New arrangements will have to emerge faster than previously, because things are deteriorating fast.
Acknowledgements Thanks to The Pew Charitable Trusts and the Paul G. Allen Family Foundation for support Thanks to other funding sources: FAO, US Western Pacific Fisheries Management Council, EU-Parliament, UNEP, BOBLME, MAVA Foundation, Rockefeller Foundation, WWF Thanks to all members of the Sea Around Us, past and present sorry, I ran out of pictures. and thanks to many other colleagues visit us at www.seaaroundus.org