Medidas de Gestao das Pescarias Marinhas e Aquicultura 2019 The State of World Fisheries and Aquaculture 2018 | Page 109

THE STATE OF WORLD FISHERIES AND AQUACULTURE 2018
BOX 5
ESTIMATING TOTAL FISH CATCHES AND THEIR MEANING
FAO recognizes the potential value of catch
reconstructions, especially for drawing attention to
problematic statistics. Such exercises may provide
additional information on fisheries’ contributions to
food security and nutrition as well as discarded
catches, help identify fishery subsectors that are not
well covered in national data collection systems and so
help countries refine their data collection
methodologies and, if necessary, revise their statistics.
However, the large uncertainty involved must be
recognized, especially in interpreting contrasting trends
derived from differing and highly debated
methodological approaches (see Ye et al., 2017). FAO
recommends that statistics from primary sources (i.e.
countries’ and RFBs’ submissions) be clearly separated
from data derived from secondary studies to avoid
confusion in their interpretation by the user community.
Interpreting trends in global capture fisheries
production requires caution, primarily because they are
the sum of thousands of combinations of species,
fishing areas, fleets and countries and influenced by
management measures that may or may not be in
operation over time. It is well known that catches do
not necessarily reflect abundance and thus stock status.
It would be misleading to associate catch trends with
stock sustainability without considering changes in
fishing effort, including those caused by management
regulations (and their implementation over time), as
overfishing and efficient management systems designed
to rebuild stocks can both result in a decline in catch. It
is for this reason that the FAO (2016c) interpretation
that global marine capture fisheries have been stable
over the past 30 years (especially if the highly variable
and abundant anchoveta, Engraulis ringens, is
excluded) does not imply that the state of the resources
is also stable (Ye et al., 2017). It is recognized that
well-assessed fisheries have been moving towards
sustainability in recent decades (Costello et al., 2012;
Worm et al., 2009). However, over 30 percent of
global stocks are overfished, a share that has been
increasing over time. A change in direction is crucial to
reach the targets of SDG 14.
FAO maintains the only global capture production
database available. The database is a collection of
nominal catches, which are defined as the net weight
of the quantities landed, as recorded at the time of
landing, converted to their live-weight equivalents. The
database is primarily based on the official statistics
submitted by member countries, but these may be
complemented or replaced with data from other
sources (e.g. “best scientific data” from RFBs). The
concepts and standards for the collection and
processing of FAO fishery statistics are set by the FAO
Coordinating Working Party on Fishery Statistics
(CWP) (Garibaldi, 2012).
FAO capture statistics were established primarily
to determine the contribution of fisheries to food
supply. It is recognized that the FAO capture
database does not include all fish caught in the
wild, as it omits the portion of the catch that is
discarded at sea and catches from illegal,
unreported or unregulated (IUU) fisheries, which are
both inherently difficult to estimate. In this regard,
FAO has commissioned several evaluations of global
discards in which the total volumes differed
significantly, a reflection of the methodological
difficulties associated with their estimation (Kelleher,
2005). FAO also convened a workshop in 2015
aimed at updating global IUU estimates, which
concluded that the lack of robust and consistent
methodology and the intrinsic lack of transparency
in IUU fishing result in highly uncertain estimates
(FAO, 2015c).
In recent years a number of studies have attempted
to estimate the volume of total removals (e.g. Pauly and
Zeller, 2016; Watson and Tidd, 2018), which
fundamentally requires estimation of discards at sea
and IUU fishing with geographical and temporal
precision. These exercises conclude that the amount of
fish entering food networks may be much larger than
the reported statistics indicate, but diverge on the
temporal trends in total removals, largely as a result of
differing methodological assumptions for IUU
estimation (discussed in detail in Ye et al., 2017).
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