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Systematic Distortions in World Fisheries Catch Trends


Abstract and Figures

Over 75% of the world marine fisheries catch (over 80 million tonnes per year) is sold on international markets, in contrast to other food commodities (such as rice). At present, only one institution, the Food and Agriculture Organization of the United Nations (FAO) maintains global fisheries statistics. As an intergovernmental organization, however, FAO must generally rely on the statistics provided by member countries, even if it is doubtful that these correspond to reality. Here we show that misreporting by countries with large fisheries, combined with the large and widely fluctuating catch of species such as the Peruvian anchoveta, can cause globally spurious trends. Such trends influence unwise investment decisions by firms in the fishing sector and by banks, and prevent the effective management of international fisheries.
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We thank J. Watson and M. Murao for careful reading of the manuscript. This work was
partially supported by the Research for the Future program run by the Japan Society for
Promotion of Science (T.K.), the Special Coordination Funds (``Molecular Sensors for
Aero-Thermodynamic Research''; H.O.) and Scienti®c Research (H.O.) of the Ministry of
Education, Culture, Sports, Science and Technology.
Correspondence and requests for materials should be addressed to T.K.
letters to nature
VOL 414
29 NOVEMBER 2001
Systematic distortions in world
®sheries catch trends
Reg Watson* & Daniel Pauly*
* Fisheries Centre, 2204 Main Mall, University of British Columbia, Vancouver,
British Columbia V6T 1Z4, Canada
Over 75% of the world marine ®sheries catch (over 80 million
tonnes per year) is sold on international markets, in contrast to
other food commodities (such as rice)
. At present, only one
institution, the Food and Agriculture Organization of the United
Nations (FAO) maintains global ®sheries statistics. As an inter-
governmental organization, however, FAO must generally rely on
the statistics provided by member countries, even if it is doubtful
that these correspond to reality. Here we show that misreporting
by countries with large ®sheries, combined with the large and
widely ¯uctuating catch of species such as the Peruvian anchoveta,
can cause globally spurious trends. Such trends in¯uence unwise
investment decisions by ®rms in the ®shing sector and by
banks, and prevent the effective management of international
World ®sheries catches have greatly increased since 1950, when
the FAO of the United Nations began reporting global ®gures
. The
reported catch increases were greatest in the 1960s, when the
traditional ®shing grounds of the North Atlantic and North Paci®c
became fully exploited, and new ®sheries opened at lower latitudes
and in the Southern Hemisphere. Global catches increased more
slowly after the 1972 collapse of the Peruvian anchoveta ®shery
, the
®rst ®shery collapse that had repercussions on global supply and
prices of ®shmeal (Fig. 1a). Even taking into account the variability
of the anchoveta, global catches were therefore widely expected to
plateau in the 1990s at values of around 80 million tonnes, especially
as this ®gure, combined with estimated discards of 16±40 million
, matched the global potential estimates published since the
1960s (ref. 6). Yet the global catches reported by the FAO generally
increased through the 1990s, driven largely by catch reports from
These reports appear suspicious for the following three reasons:
(1) The major ®sh populations along the Chinese coast for which
assessments were available had been classi®ed as overexploited
decades ago, and ®shing effort has since continued to climb
; (2)
Estimates of catch per unit of effort based on of®cial catch and effort
statistics were constant in the Yellow, East China and South China
seas from 1980 to 1995 (ref. 9), that is, during a period of
continually increasing ®shing effort and reported catches, and in
contrast to declining abundance estimates based on survey data
; (3)
Re-expressing the of®cially reported catches from Chinese waters on
1970 1975 1980 1985 1990 1995
Global catch (× 10
Corrected, no anchoveta
El Nino
1970 1975 1980 1985 1990 1995
Chinese catch (× 10
Overall marine
EEZ uncorrected
EEZ corrected
Constant catch
El Nino
Figure 1 Time series of global and Chinese marine ®sheries catches (1950 to present).
a, Global reported catch, with and without the highly variable Peruvian anchoveta.
Uncorrected ®gures are from FAO (ref. 3); corrected values were obtained by replacing
FAO ®gures by estimates from b. The response to the 1982±83 El Nin
Oscillation (ENSO) is not visible as anchoveta biomass levels, and hence catches were still
very low from the effect of the previous ENSO in 1972 (ref. 4). b, Reported Chinese
catches (from China's exclusive economic zone (EEZ) and distant water ®sheries)
increased exponentially from the mid-1980s to 1998, when the `zero-growth policy' was
introduced. The corrected values for the Chinese EEZ were estimated from the general
linear model described in the Methods section.
© 2001 Macmillan Magazines Ltd
letters to nature
VOL 414
29 NOVEMBER 2001
| 535
a per-area basis leads to catches far higher than would be expected
by comparison with similar areas (in terms of latitude, depth,
primary production) in other parts of the world.
We investigated the third reason in some detail by generating
world ®sheries catch maps on the basis of FAO ®sheries catch
statistics for every year since 1950 (see Fig. 2a for a 1998 example).
A statistical model was used to describe relationships between
oceanographic and other factors, and the mapped catch. Most
high-catch areas of the world were correctly predicted by the
model. These areas typically had very high primary productivity
rates driven by coastal upwellings, like those off Peru, supporting a
large reduction ®shery for the planktivorous anchoveta Engraulis
. The exception was the waters along the Chinese coast.
Here, the high catches could not be explained by the model using
oceanographic or other factors. Yet the catch statistics provided to
FAO by China have continued to increase from the mid-1980s
until 1998 when, under domestic and international criticism, the
government proclaimed a `zero-growth policy' explicitly stating
that reported catches would remain frozen at their 1998 value
(Fig. 1b)
Mapping the difference between expected (that is, modelled)
catches and those mapped from reported statistics showed large
areas along the Chinese coast that had differences greater than
5 tonnes km
. Overall, the statistical model for 1999 pre-
dicted a catch of 5.5 million tonnes, against an of®cial report of
10.1 million tonnes (see Fig. 1b for earlier years). Although
China was not the only FAO member country reporting relatively
high catches, their large absolute value strongly affects the global
For a number of obvious reasons, ®shers usually tend to under-
report their catches, and consequently, most countries can be
presumed to under-report their catches to FAO. Thus we wondered
why China should differ from most other countries in this way. We
believe that explanation lies in China's socialist economy, in which
the state entities that monitor the economy are also given the task of
increasing its output
. Until recently, Chinese of®cials, at all levels,
have tended to be promoted on the basis of production increases
from their areas or production units
. This practice, which origi-
nated with the founding of the People's Republic of China in 1949,
became more widespread since the onset of agricultural reforms
(tonnes km
< 1
(tonnes km
< 1
Figure 2 Maps used to correct Chinese marine ®sheries catch in Fig. 1b. a, Map of
global catches reported by FAO for 1998, generated by the rule-based algorithm
described in the Methods section. We note the anomalously high values along the
Chinese coast, comparable in intensity (not area covered) to the extremely productive
Peruvian upwelling system. b, Map of differences in southeast and northeast Asia
between the catches reported in a and those predicted by the model described in the
Methods section.
© 2001 Macmillan Magazines Ltd
letters to nature
VOL 414
29 NOVEMBER 2001
that freed the agricultural sector from state directives in the late
1970s (refs 10, 11).
The Chinese central government appears to be well aware of this
problem, and its 1998 `zero-growth policy' was partly intended to
prevent over-reporting. Thus, the of®cial ®sheries catches for 1999±
2000 are precisely the same as in 1998 (Fig. 1b), and will be for the
next few years. Such measures, although well motivated, do not
inspire con®dence in of®cial statistics, past or present.
The substitution of the more realistic estimated series of Chinese
catches into the FAO ®sheries statistics led to global catch estimates
which, although ¯uctuating, have tended to decline by 0.36 million
tonnes year
since 1988 (rather than increase by 0.33 million
tonnes year
, as suggested by the uncorrected data). The global
downward trend becomes clearer when the catches of a single
species, the Peruvian anchoveta, which is known to be affected by
El Nin
o/Southern Oscillation events, is subtracted (see Fig. 1a). In
this case, a signi®cant (P , 0:01), and so far undocumented down-
ward trend of 0.66 million tonnes year
becomes apparent for all
other species and ®sheries. This is consistent with other accounts of
worldwide declines of ®sheries
Ironically, it is likely that, at the lowest levels (individual ®shers),
catches are under-reported in China as elsewhere in the world. The
production targets caused these reports to be exaggerated. At some
times these two distortions may perhaps have cancelled each other
out, and an accurate report of catches may have been submitted to
FAO. Since the early 1990s, however, the exaggerations have appar-
ently far exceeded any initial under-reporting.
The greatest impact of in¯ated global catch statistics is the
complacency that it engenders. There seems little need for public
concern, or intervention by international agencies, if the world's
®sheries are keeping pace with people's needs. If, however, as the
adjusted ®gures demonstrate, the catches of world ®sheries are in
general decline, then there is a clear need to act. The oceans should
continue to provide for a substantial portion of the world's protein
needs. The present trends of over®shing, wide-scale disruption of
coastal habitats and the rapid expansion of non-sustainable
aquaculture enterprises
, however, threaten the world's food
Data processing involved a disaggregation of global ®sheries catch statistics ®rstly into
detailed taxonomic groups, and then into ®ne-scale spatial cells (a half-degree of latitude
by a half-degree of longitude), using a variety of databases and systematic rules
. The
spatially disaggregated catches provided the basis for a general linear model of ®sheries
catches (see below). The model predicted the likely catches in the spatial cells in the
Chinese exclusive economic zone (EEZ), thus providing an estimate of Chinese catches
(including Hong Kong and Macau, but excluding Taiwan).
Data sources
Fisheries catch statistics were provided by the FAO (FishStat
and `Atlas of Tuna and
Bill®sh Catches',®/atlas/tunabill/english/home/htm). The spatial cells
were described by depth (US National Geophysical Data Center), primary productivity
(Joint Research Centre of the European Commission Space Applications InstituteÐ
Marine Environment Unit,,
biogeochemical provinces
, the presence of ice (US National Snow and Ice Data Center,, surface temperature (NOAA's Marine Atlas, http://www.nodc.noaa.
gov/OC5/data_woa.html), and an upwelling index calculated for each cell by multiplying
negative deviations in surface temperature (from the average for that latitude and ocean) by
the primary productivity in that cell. Fishing access rights were determined using maps of
the exclusive economic zones (EEZ) of coastal states
and a database of ®shing access
Taxonomic disaggregation
The ®sheries statistics of several nations commonly include a large fraction of catches in
`miscellaneous' categories. Chinese catches so reported were disaggregated on the basis of
the breakdown provided by its two nearest maritime neighbours with detailed marine
®sheries statistics (Taiwan and South Korea)
. Assigning catches to lower taxa allowed the
use of biological information in the spatial disaggregation process.
Spatial disaggregation
A database of the global distribution of commercial ®sheries species was developed using
information from a variety of sources including the FAO, FishBase
and experts on various
resource species or groups. Some distributions were speci®c; others provided depth or
latitudinal limits, or simple presence/absence data. The spatial disaggregation process
determined the intersection set of spatial cells within the broad statistical area for which
the statistics were provided to FAO, the global distribution of the reported species, and the
cells to which the reporting nation had access through ®shing agreements
. The reported
catch tonnage was then proportioned within this set of cells.
Catch predictions
A general linear model was developed in the software package S-Plus
. The model relates
log ®sheries catch (in tonnes km
) for each cell (the dependent variable) to depth,
primary productivity, ice cover, surface temperature, latitude, distance from shore,
upwelling index (the continuous predictor variables), 33 oceanic biogeochemical
provinces and one global coastal `biome'
including most of the area covered by the
world's EEZs, including China's (the categorical predictor variables). Fishing effort was
not used in the prediction and catches were assumed to be generally close to their
maximum biologically sustainable limits. The additive and variance stabilizing transfor-
mation (AVAS) routine of S-Plus
was used to identify transformations ensuring linearity
between the dependent and explanatory variables, and the model was then used to predict
the catch from each spatial cell. Those from Chinese waters were combined, then
compared with the catches obtained from the rule-based spatial disaggregation described
Trend analyses
The estimates of recent trends of global catch were estimated by linear regression of catch
versus year, for the period from 1988 (highest catches, anchoveta excluded) to 1999 (last
year with FAO data), for uncorrected global marine catches, global marine catches
adjusted for Chinese over-reporting, and adjusted catches minus the catch of Peruvian
Received 30 July; accepted 28 September 2001.
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We thank V. Christensen for the upwelling index, and A. Gelchu for the species
distribution shape ®les used here. We also thank our colleagues in the `Sea Around Us'
Project. This work was supported by the Pew Charitable Trusts through the `Sea Around
Us' Project, Fisheries Centre, University of British Columbia. D.P. also acknowledges
support from the National Science and Engineering Council of Canada.
Correspondence and requests for materials should be addressed to R.W.
(e-mail: r.watson@®
© 2001 Macmillan Magazines Ltd
環團找碴 ±2錯誤一籮筐?
2010.03.03 06:05 am
09年中人口密度排名在台灣前面的依序為: 摩納哥、澳門、新加坡、香港、巴林、馬爾他、孟
加拉、馬爾地夫、Channel Islands、巴貝多、巴勒斯坦等11地。她也對片中所指「台灣土地
該片所述「台灣氣溫上升攝氏一, 降雨增加100%」,徐光蓉認為過於武斷,她也抨擊該片
不當的誇耀「學術性」。該片學者顧問Stephen Schneider,擔任IPCC三個工作小組中第二
平獎由高爾與IPCC這單位共同獲得,由印度籍主席Rajendra Pachauri代表IPCC領獎。Sch
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Data-limited methods are being developed rapidly to cater to a range of data types and stock characteristics. One class of these methods is catch-only methods (COMs), which seek to determine stock status based largely, or exclusively, on catch histories. Although catch data are the most common information for a fishery, they are susceptible to large errors. Understanding the performance of COMs when catch is mis-specified is necessary before they can be used in fisheries management. This study constructed a simulation-estimation framework to evaluate the performance of two types of COMs, Catch-MSY (CMSY) and catch-only boosted regression trees (zBRT), in inferring stock biomass status (B/BMSY) with consideration of different forms of catch errors, fishing patterns, and prior information. The results showed both COMs tended to bias the estimates of B/BMSY regardless of types of catch errors. The estimation performance of COMs was robust to the constant reporting rate across all fishing patterns, which means constant catch over- or under-reporting would not affect the COM assessment. zBRT showed high sensitivity to fishing patterns and performed best when fishing mortality was constant. CMSY yielded underestimation in most cases, but use of a narrow and informative prior on final depletion improved accuracy in recent years. Neither COM performed well in correctly identifying categorical biomass status (overfished vs. not overfished) across assessment years. We caution that improving catch quality would not improve the estimation of COMs and do not advocate for the application of COMs due to their poor performance.
The sustainable exploitation of the marine environment depends upon our capacity to develop systems of management with predictable outcomes. Unfortunately, marine ecosystems are highly dynamic and this property could conflict with the objective of sustainable exploitation. This book investigates the theory that the population and behavioural dynamics of predators at the upper end of marine food chains can be used to assist with management. Since these species integrate the dynamics of marine ecosystems across a wide range of spatial and temporal scales, they offer new sources of information that can be formally used in setting management objectives. This book examines the current advances in the understanding of the ecology of marine predators and will investigate how information from these species could be used in management.
Inspired by the work of the renowned fisheries scientist Daniel Pauly, this book provides a detailed overview of ecosystem-based management of fisheries. It explores the complex and interdisciplinary nature of the subject by bringing together contributions from some of the world's leading fisheries scientists, managers and conservationists. Combining both research reviews and opinion pieces, and reflecting the breadth of Pauly's influence within the field, the book illustrates the range of issues associated with the implementation of the ecosystem approach and the challenge of long-term sustainability. Topics covered include global biodiversity, the impact of human actions on marine life, the implications for economic and social systems and the role of science in communicating and shaping ocean policy to preserve resources for the future. This book provides a complete and essential overview for advanced researchers and those just entering the field.
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Global production of farmed fish and shellfish has more than doubled in the past 15 years. Many people believe that such growth relieves pressure on ocean fisheries, but the opposite is true for some types of aquaculture. Farming carnivorous species requires large inputs of wild fish for feed. Some aquaculture systems also reduce wild fish supplies through habitat modification, wild seedstock collection and other ecological impacts. On balance, global aquaculture production still adds to world fish supplies; however, if the growing aquaculture industry is to sustain its contribution to world fish supplies, it must reduce wild fish inputs in feed and adopt more ecologically sound management practices.
Cohort analysis is used to reconstruct the population dynamics of the large yellow croaker (Pseudosciaena crocea (Richardson)) in the China Sea, using age-composition and catch data from 1957 to 1979. A precondition for cohort analysis is that natural mortality M and terminal catch- ability coefficient q be known. These are estimated from age-composition data for two relatively stable periods with widely different exploitation rates. Cohort analysis suggested the virginal stock size of large yellow croaker was about 730,000 t. The biomass remained at a high stable level (about 480,000 t) until the middle 1960’s; the stock then decreased rapidly because of increasing fishing effort. Recruitment apparently increased at first as the stock declined, but there are signs of decreased recruitment at the current low stock size. The present stock is about 200,000 t, the lowest on record. Different recovery and management strategies were evaluated by computer simulation. The maximum equilibrium yield is probably 95,000-100,000 t, associated with an equilibrium biomass of 390,000 t. considering environmental effects on recruitment, the yield is likely to fluctuate between 70,000 and 130,000 t. To maintain the maximum average yield, the fishing effort should be equivalent to approximately the present annual fishing capacity of 1,000 pairs of 60- horsepower, paired trawlers in the Zhowshon district. About 15 years will be needed for the stock to recover to optimum equilibrium biomass if the optimum long-term effort is maintained.
Exceptionally clear and well-written chapters provide engaging discussions of the methods of accessing, generating, and analyzing social science data, using methods ranging from reflexive historical analysis to critical ethnography. Reflecting on their own research experiences, the contributors offer an inside, applied perspective on how research topics, evidence, and methods intertwine to produce knowledge in the social sciences.
Conference Paper
Picosecond resonance Raman spectroscopy has been used to obtain structural information on the primary photointermediates of bacteriorhodopsin. A synchronously pumped dye laser was amplified at 50 Hz to produce a probe pulse at 589 nm. A second, spectrally distinct, pump pulse at 550 nm was generated by amplification of a 10 nm portion of a continuum produced from the probe pulse. This apparatus was used to record spectra of the J, K, and KL intermediates. The J spectrum exhibits strong hydrogen out-of-plane (HOOP) intensity and the fingerprint region consists of a broad series of lines centered at 1180 cm-1. By 3 ps, K has formed and the relative HOOP intensity decreases while the fingerprint collapses to a single mode at 1190 cm-1, characteristic of a 13-cis chromophore. These results argue that J contains a highly twisted chromophore which relaxes upon conversion to K and that isomerization is complete within 3 ps. Between 3 ps and 3.7 ns there is a resurgence in HOOP intensity and the ethylenic frequency rises from 1518 to 1521 cm-1 indicating the conversion of K to KL.
The resonance Raman (RR) spectra in the fingerprint region (1100–1300 cm−1) are reported for the initial, picosecond interval of the bacteriorhodopsin (BR) photocycle during which the J-625 and K-590 intermediates are formed. These are the first RR features assigned to J-625 while the RR bands assignable to K-590 alone are clarified with respect to previous studies. The assignment of RR features to J-625 and K-590 is based on the results of two-laser, picosecond time-resolved resonance Raman (PTR3) experiments designed to separate RR bands of K-590 from other species. The instrumental design underlying PTR3 experiments and the associated advantages for analyzing time-resolved data are described. The PTR3 data in the fingerprint region suggest that neither J-625 nor K-590 contain all-trans retinal and therefore, establish that the primary BR photocycle event involves a configurational change in the retinal chromophore. The RR fingerprint bands assignable to J-625 and K-590, however, differ from one another indicating that the two intermediates do not contain retinal in the same configurational or conformational form and that a second change in retinal structure occurs over the initial 10 ps of the photocycle. The identification of either intermediate in terms of an absolute configuration (e.g., 13-cis retinal) or conformation remains unresolved.
Resonance Raman spectroscopy has been used to obtain structural and kinetic information on the primary photointermediates of bacteriorhodopsin with 3-ps time resolution. A synchronously pumped dye laser was amplified at 50 Hz to produce a probe pulse at 589 nm while a second, spectrally distinct, pump pulse at 550 nm was generated by amplification of a 10-nm portion of a continuum produced from the probe pulse. This apparatus was used to record Stokes Raman spectra of the photoproduct from 0 ps to 13 ns as well as anti-Stokes spectra from 0 to 10 ps. At 0 ps, the Stokes spectrum, assigned to J, has strong hydrogen out-of-plane (HOOP) intensity at 1,000 and 956 cm{sup {minus}1}, the fingerprint region consists of a broad band of lines from 1,155 to 1,200 cm{sup {minus}1}, and the ethylenic line is found at 1,518 cm{sup {minus}1}. By 3 ps the relative HOOP intensity drops to its lowest value and the fingerprint collapses to a single strong mode at 1,189 cm{sup {minus}1}, while the ethylenic remains at 1,518 cm{sup {minus}1}. The lifetime of the initially strong anti-Stokes scattering is {approximately}2.5 ps, indicating that the J {yields} K transition is due, in large part, to vibrational cooling of the chromophore. The authors conclude that the chromophore in J is highly twisted and thermally excited but that it cools and conformationally relaxes to a more planar 13-cis chromophore within 3 ps to form K. Between 3 and 40 ps there is a resurgence in Stokes HOOP intensity which remains large and nearly constant thereafter and the ethylenic frequency shifts from 1,518 to 1,521 cm{sup {minus}1} within 200 ps. These changes are assigned to the conversion of K to a more twisted and bluer-absorbing KL species between 20 and 100 ps which must be caused by an isomerization-induced protein conformational change.