Denmark Request on methodologies relevant to interactions between eiders and blue mussels

ICES has been requested to advise on methodologies aimed at evaluating the interaction between the blue mussel fishery and the mussel eating bird populations in Natura 2000 sites in the Danish waters thus:

estimation of the energetic requirements of Eiders and other mussel eating bird species in the Danish part of the Wadden Sea, including assessment of the amount of blue mussel necessary for the eiders;

estimation of the energetic requirements of Eiders and other blue mussel eating bird species, in the NATURA 2000 sites outside the Wadden Sea; and

estimation of the blue mussel stock and annual blue mussel production in the Danish part of Wadden Sea and in other relevant Danish NATURA 2000 sites.

The following answer is a technical service to Denmark and is developed by the relevant expert groups. The Advisory Committee is satisfied that these groups are the competent bodies to provide the answer.

The Working Group of Sea Bird Ecology (WGSE) addressed the first two parts of thse term of reference. The recommendations provided by WGSE follow the requests closely, and are therefore limited to a description of suggested methodologies for estimating energy requirements of mussel-feeding waterbirds, see Section 11.2.1.

While WGSE has not attempted to estimate these quantities for the Danish Wadden Sea and Natura 2000 sites, such estimations have already been attempted for common eiders in the Dutch Wadden Sea (Brinkman, 2003).

The ICES Benthic Ecology Working Group (BEWG) has addressed the third part of the term of reference – appropriate methodology for the assessment of quantities of mussels consumed, see section 11.2.2.