Major Trends in Global Marine Fisheries

1
Major Trends in Global Marine Fisheries

• by
• Daniel Pauly
• Sea Around Us Project
• Fisheries Centre,
• University of British Columbia
• Vancouver, Canada
• Third IGBP Congress
• Connectivities in the Earth Systems Banff, 25
  June 2003

2
Fisheries, globally, are not doing too well. For
example, virtually all species at or near the top
of North Atlantic food webs have been depleted by
excess fishing, as illustrated here by trends in
biomass (blue) and fishing mortality (red) from
single-species assessments.
Trends based on data from R.A. Myer, Dalhousie
University, Halifax.
3
We can generalize this by using the FAO catch
time series in FishBase 2000 and some simple
definitions
Definitions by R. Froese, IfM, Kiel, Germany
4
This shows a steady erosion of fisheries
worldwide. Thus, global fisheries are in a major
crisis, and the problem is growing rapidly.
Analysis by R. Froese, IfM, Kiel, Germany
5
And yet, the global catch statistics assembled by
FAO so far did not seem to add up to a globally
declining catch
Indeed, global catches appeared to increase in
the 1990s.
Based on the FAO data for 2000, with
approximations for discards and unreported
catches.
6
We can address this using the global FAO dataset.
However, it must be transformed in its original
version, the catches are presented in a grid too
coarse for ecological analyses.
7
First, we defined small spatial cells, which can
be mixed and matched as needed. We chose ½
lat./long cells (of which there are over 150,000
in the world ocean).
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Then, we considered that most catches come from
within the Exclusive Economic Zones of maritime
countries. We have a global database of fishing
access agreements.
Now, fish can be caught only where they occur
9
For each of over 1200 taxa in the FAO database,
we created a distribution area (mapped as a GIS
object). Combining all this we can

• Assess where the catch of a given taxon can
  possibly have come from
• Identify the overlap area between this
  distribution and the EEZs to which the a given
  countrys fleet have access
• Assign the catch to the ½ degree Lat./Long. cells
  from which the catch can have originated.

Or put differently
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Taxon (what)
FAO Area (where)
Country (who)
Taxon distribution database
Spatial reference database
Fishing access database
This routine now assigns over 99 of FAO global
marine catches to ½ degree spatial cells, and we
are still improving the underlying databases
Common spatial cells?
NO
Improve databases
YES
Assign catch rate to common cells
11
Then, we used a multivariate statistical model to
try to reproduce our rule-based catch map, using
depth, primary production, etc, to predict
catches...
It worked everywhere, except for East Asian
waters, where the discrepancies were huge.
12
Correcting for this showed that global fisheries
catches have been declining since the late 1980s
..which contradicted the official reports used in
global assessments, notably those generated by
the Food and Agriculture Organization of
the United Nations (Watson and Pauly, Nature,
2001).
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Now, turning to the ecosystems underlying
fisheries they can be represented as pyramids,
where the volume at each level indicates the
amount of biological production, here for the
North Sea.
Note change in number of levels, etc...
Also note that the corresponding pyramid for the
North Sea in 2001 would be about half the size
of that for 1981. Generalizing this.
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(t/km2)
Biomass of table fish in 1900 (Christensen et
al. 2003 Fish and Fisheries)
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and in 2000.
So the fisheries moved on
16
The fish wealth of West Africa has long attracted
distant water fleets from other continents
Number of country access years by area,
1960-1969
17
and these have increased tremendously over the
years
Number of country access years by area,
1980-1989
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finally reaching the present, staggering levels.
Number of country access years by area,
1990-1999
19
The result was predicable strong biomass
declines.
Christensen et al. (2002). Dakar Conf.
Proceedings (in press)
20
As an aside here is an example of the
distribution of gross returns between a small
West African country and the European Union
(Spain, France).
21
As for Southeast Asia
1960
2000
Christensen et al. (in press)
22
Thus, consumers in the North have not noticed
much any fisheries crisis while most seafood is
traded between the EU, the USA and Japan, the
South has so far met the shortfall in the
North.
23
Fisheries catches would be declining faster, were
it not for the expansion of fishing into deeper
areas and further offshore, especially in the
Southern Hemisphere
24
Mean depth of catch (m)
Here is an illustration of this expansion toward
greater depth, especially in the Southern
Hemisphere
25
And here is another representation of the same
trend, extrapolated to 2050. Clearly, we dont
want to go there. However, turning that around
will be extremely difficult.
Depth (m)
Percentage fished
Year
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Now consider that ecosystem fluxes move up
trophic pyramids
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Thus, we we can estimate (from the catch series
of FAO) and trophic levels in FishBase
(www.fishbase.org)) the mean trophic level of
global fisheries landings. This is declining
globally
Pauly et al. Science, 1998
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Moreover, this process, wherein fisheries catches
are increasingly based on organisms low in the
food web, now known as fishing down marine food
webs, has been recently shown to be stronger and
more widespread than originally estimated
Northwest Atlantic
Northeast Atlantic
Pauly et al. Science, 1998
29
Indeed, the trend toward fishing down is
everywhere
30
Now to aquaculture, especially mariculture, which
has grown tremendously in the last decades and
which therefore may be seen as the solution to
our fish supply problem
Production (106 t)
31
There are two problems with this

• The overwhelming bulk of reported increase in
  global aquaculture production is due to reports
  from China (and there are good reasons to assume
  that over-reporting may also affect these
  statistics) and
• In most other parts of the world, aquaculture
  growth is driven by increasing production of
  carnivorous fishes (e.g., salmon, bass), i.e., by
  fish, which to reach market size, must consume
  more fish products than they themselves
  contribute.

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The latter trend, which may be called farming up
the food web, is documented here for a selection
of major producing countries
Note absence of an increasing trend for the USA,
due to a high production of (low trophic level)
catfishes (Pauly et al. 2001. Conservation
Biology in Practice 2(4) 25).
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Thus, with business as usual, the global annual
supply of seafood per person may well decline as
shown here...
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There are no techno-fixes to the global fisheries
crisis. We must deal with its root cause,
illustrated by this map, where areas where no
fishing whatsoever is permitted are shown in
green
..and visit us at www.saup. fisheries.ubc.ca for
more information
Thank you.