Medidas de Gestao das Pescarias Marinhas e Aquicultura 2019 The State of World Fisheries and Aquaculture 2018 | Page 113

THE STATE OF WORLD FISHERIES AND AQUACULTURE 2018
approach to the assessment, which means
including multi-species considerations as well as
social, economic and environmental factors, is
also a challenge.
builds on assessments from various sources,
including those of national institutions and RFBs.
However, many species and large ocean areas are
not covered by any form of assessment; these are
assessed with simple, non-model-based
approaches mostly using catch trends from the
FAO global capture database. The results are
published ever y two years in The State of World
Fisheries and Aquaculture (see Part 1). The global
assessment was used, for example, as a data
source for one of the indicators of the United
Nations Millennium Development Goals (UN,
2015b) and provides main inputs to the United
Nations World Ocean Assessment (UN, 2018b).
Collecting minimal data. Stock status cannot be
accurately assessed without sufficient data. High-
qualit y fisheries data are often not available,
particularly in developing countries. In some
situations, minimal data such as total catch and
number of vessels involved in a fisher y are not
even recorded. Stock assessment reliabilit y can
improve if basic catch data are augmented by
other data such as catch per unit of effort (CPUE)
for at least one involved f leet, length or age
frequency distribution of species caught, and
fisher y-independent sur vey data, although the
last are usually expensive to collect.
Challenges
Stock assessment is not properly carried out in
many developing countries, and assessed stocks
represent only about 25 percent of world catches
(Branch et al., 2011). Indeed, assessing the status
of fish stocks is not easy, as it is not only data
demanding, but also technically intensive and
financially costly. To increase the coverage of
stock assessment and monitoring, the following
multifaceted challenges need to be addressed.
Institutional and human capacity building. The numerical
modelling skills required for stock assessment are
often in short supply and cannot be instilled
through brief training. Many developing
countries lack modelling professionals, and this
shortage can only be addressed through long-
term planning at the institutional level. A root
cause of poor institutional capacit y is the lack of
understanding of modelling work and/or
appreciation of the utilit y of its results by policy-
makers and even other fisher y scientists, and the
consequent failure to use it for management
purposes or to regard it as a priorit y.
Strengthened institutional capacit y along the
entire intellectual chain from assessment to
policy implementation is needed to facilitate
effective fisheries management.
Overcoming technical limitations. Stock status assessment
and monitoring largely rely on classical
assessment methods. Describing population
dynamics and estimating stock status require
refined numerical skills for the use of
mathematical and statistical models, together
with comprehensive fisher y-dependent data, such
as catch and fishing effort derived from reg ular
fisher y monitoring, as well as fisher y-
independent data on biomass trends, natural
mortalit y, growth, gear selectivit y and
recruitment. Increasing attention is being given
to improving fisher y-dependent data, for example
through the use of the latest technolog y,
including satellites and smartphones, in data
collection and transmission. Traditional
assessment methods nevertheless continue to be
demanding of expertise and of data which are
expensive to collect. Recent advances have
focused on methods that can be applied to data-
limited fisheries (Rosenberg et al., 2014),
including the development of empirical indicators
to inform management. A technical breakthrough
is needed, however, to make data-limited
methods as reliable as classical methods in
determining stock status. Taking an ecosystem
Complexity of shared stocks and migratory species. Many fish
species migrate and straddle national EEZs and
areas beyond national jurisdiction (high seas). For
these species, the challenges of assessment,
monitoring and management are different from
those for species occurring only within EEZs.
Migratory species occur in different areas at
different life stages. However, because they are
considered a single biological unit, fishing in any
area will affect the whole stock, and integrated
management among all areas is thus required. To
achieve this goal, political agreements for joint
management among the concerned countries must
be strengthened or established. Mechanisms are
then required for cooperation in data collection
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