Interim report of the HELCOM CORESET project

56
Weighting
For Nordic Costal multimesh nets, the analyses are based on weighted means of data from all depth strata,
in order to account for the depth-stratifi ed sampling design.
Corrections
For all data sets, the relationship between of the indicators to local temperature and salinity was checked
prior to further analyses. If the correlation was signifi cant, further analyses were performed based on the
remaining variation (regression residuals).
Weaknesses/gaps
The current monitoring program does not provide full spatial coverage, and is mainly targeting areas with
relatively low levels of direct anthropogenic infl uence. Currently, methods for extrapolating the results to
areas without monitoring are under development. Given the current state of knowledge, it is suggested
that the status classifi cations achieved for monitored areas are extrapolated to areas without monitoring
by direct interpolation in combination with expert opinion. Alternatively, additional data sources such as
commercial catch statistics based on EU-data collection system, coastal echo sounding, etc. might serve
as a complement if the data proves to be of enough quality to assess the biodiversity of coastal fi sh communities.
Extended data collection with a focus on polluted areas is being performed in 2011 and will bring
further knowledge on natural environmental factors driving spatial variation in indicator values and the
relationship of indicators to anthropogenic pressure factors, such as eutrophication and fi shing pressure.
References
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Trends in coastal fi sh stocks in the Blaltic Sea. Boreal Environment Research, 11: 13-25.
Appelberg, M., Holmqvist, M. and Forsgren, G. 2003. An alternative strategy for coastal fi sh monitoring in
the Baltic Sea. ICES Annual Scicence Conferens, Sept. 2003, Tallinn, Estonia. 13 p.
Carstensen, J. 2007. Statistical principles for ecological status classifi cation of Water Framework Directive
monitoring data. Marien Pollution Bullentin, 55: 3-15
Eriksson, B. K., Sieben, S., Eklöf, J., Ljunggren, L., Olsson, J., Casini, M., and Bergström, U. 2011. Effects of
altered offshore food webs on coastal ecosystems emphasizes the need for cross-ecosystem management.
Ambio, DOI 10.1007/s13280-011-0158-0.
HELCOM. 2011. Assessment on conservation status of coastal fi sh in the Baltic Sea 2005-2009. Submitted
to HELCOM MONAS for approval, 2011-09-19.
HELCOM. 2008. Guidelines for HELCOM coastal fi sh monitoring sampling methods.
Olsson, J., Bergström, L. and Gårdmark, A. Abiotic drivers of coastal fi sh community change during the last
four decades in the Baltic Sea. Submitted manuscript.
Pauly, D., Christensen, V., Dalsgaard, J., Froese, R. and Torres Jr., F. 1998. Fishing down marine food webs.
Science, 279: 860-863.
Rice, J.C. and Rochet, M-J. 2005. A framework for selecting a suite of indicators for fi sheries management.
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Swedish Board of Fisheries. 2011. Resurs och Miljööversikt 2011. In Swedish.