The ICES/HELCOM Working Group on Integrated Assessments of the Baltic Sea
(WGIAB) was set up as a forum for developing and combining ecosystem‐based
management efforts for the Baltic Sea, and is intended to serve as a counterpart and
support for the ICES Baltic Fisheries Assessment Working Group (WGBFAS) as well
as related HELCOM assessment efforts and projects, such as HELCOM CORESET
and HELCOM FISH PRO.
Three main tasks
To this end, WGIAB has given itself three main tasks:
1) to conduct holistic ecosystem assessments based on large multivariate
2) to consider the use of ecosystem modelling in the assessment framework;
3) to develop adaptive management strategies for the different Baltic Sea ecosystems.
WGIAB has focused most of its previous work on the first two tasks, by
(i) performing multivariate analyses of ecosystem status and trends
in, until now, eight Baltic Sea subsystems, demonstrating large‐scale shifts in ecosystem
structure and functioning, and by (ii) developing
Biological Ensemble Modelling to further long‐term management advice.
During the 2011 meeting, the major activities undertaken
therefore related to Task 3. The meeting was held 4—8 April at IMEDEA in Esporles,
Spain, with 25 participants from 11 countries.
Integrated Ecosystem Assessments (IEA)
To develop adaptive management strategies for the Baltic Sea subsystems, WGIAB
has decided to follow the broader understanding of Integrated Ecosystem Assessments
(IEAs) as a full assessment‐ and management cycle.
Last year WGIAB identified indicator systems for ecosystem‐based management
as an aspect of the IEA‐cycle that was not already covered by WGIAB activities
under tasks 1 and 2. While WGIAB 2010 started working on indicator systems by
e.g. evaluating indicators proposed in relation to the EC Marine Strategy Framework
Directive and HELCOM Baltic Sea Action Plan, this meeting took a more process based
approach to development of ecosystem indicator systems.
In the IEA cycle, the
purpose of indicators is to signal when management objectives regarding ecosystem
attributes are not met. To develop such indicators,
a thorough understanding of ecosystem processes and responses to human pressures
is needed. A major goal of this meeting was therefore to start analyses towards a better
understanding of processes leading to the shifts in ecosystem structure, with the
aim to use this for future developments of indicators for an IEA cycle.
(i) Are there any discontinuous food web interactions in the Central
Baltic Sea pelagic ecosystem?
(ii) How does climate affect different trophic levels and
does it differ across basins? and
(iii) How does trophic control (bottom‐up vs. top down)
regulate different trophic levels and does it differ across basins?
In parallel, the meeting also assessed the potential to derive indicators to forewarn of
large ecosystem restructurings, by evaluating a set of proposed “early‐warning indicator"
methods on real monitoring data assembled by WGIAB. Application of six
different types of early‐warning indicators to spatio‐temporally resolved data on a
key ecosystem component in the central Baltic Sea, Pseudocalanus acuspes, showed that
no single method provided sufficient early warning in real monitoring data. Instead,
multiple methods should be applied to derive system‐specific detections of ecosystem
WGIAB also continued to develop ecosystem‐based fisheries advice. Due to large
uncertainty in recent stock assessment estimates for the Eastern Baltic (EB) cod
, WGBFAS had asked for information on environmental conditions
relevant for recruitment of Eastern Baltic cod. Based on tests of potential indicators,
WGIAB developed and assessed two indicators of abiotic conditions for cod
recruitment and growth (i.e. food levels). This showed favourable salinity conditions
for recent cod year‐classes, but poor conditions in terms of both reproductive volume
and food abundance. The assessment of the cod recruitment environment was provided
to the WGBFAS meeting to support the stock assessment. Detailed
analyses of environmentally sensitive stock‐recruitment functions were also
made for Eastern Baltic cod and some coastal fish stocks.
The meeting further pursued a WGIAB core activity, the multivariate analyses of ecosystem
status and trends, which were updated and further developed. The primary
goal of this activity during WGIAB 2011 was to advance ecosystem status and trend
analyses of coastal ecosystems across the Baltic Sea. A first review of data availability
and quality was made for nine coastal and small‐scale subsystems. Initial ecosystem
status and trend analyses were made for six of these subsystems, demonstrating
shifts in ecosystem structure in at least four systems. The databases and analyses will
be further refined by WGIAB and used in comparative analyses across systems. In
addition, the Central Baltic Sea (CBS) biotic dataset was updated to 2009. The analyses
still demonstrated the major shift to be in the end of the 1980s, with no significant
changes in food web composition in the most recent years. This suggests that the CBS
food web currently remains in an ecosystem “regime" which has been characterized
by e.g. low levels of cod and Pseudocalanus acuspes, and high sprat abundances, for
which important changes in food web function in relation to in previous “regimes"
has been shown.
In 2012 WGIAB will continue developing Integrated Ecosystem Assessment cycles for
the Baltic Sea subsystems, by (i) improving knowledge of the processes causing shifts
in ecosystem structure to further develop IEA indicators and modelling, and (ii) further
developing the multivariate ecosystem trend and status analyses and their application
to Baltic Sea subsystems.