Ecosystem Services

Denmark has a large fishing for mussels in the Limfjord; where up to 100,000 tons
are scraped up each year (Chapter 5.4.2). However, at the global level, shellfish farming
is developing rapidly, with China as the leading nation. Mussel production in Europe is
between 300,000 and 400,000 tons a year. In Europe, Spain has the largest production
of 200 000 tons. Figures from Gregersen (2007) show that about 1,300 tons were harvested
in Norway along the Skagerrak coast in 2005, and similarly between 1,000 and
1,500 tons on the Bohuslän coast in Sweden. Denmark produces some 20,000–30,000
tons of mussels each year in the Skagerrak and is a large producer of processed mussels.
The Scandinavian countries are assumed to be far below production capacity, and for
instance Norway are said to be able to increase to 100 000 tons within a few years.
In the 80’s, many mussel farmers failed due to insufficient professional commitment,
poor control of algal toxins and the lack of contact with the marked. In recent years, however,
these issues have become far better and many companies have much higher professionality
in their businesses today. This is not the least through the technique of so-called
controlled upwelling when nutrient-rich deep-water are directed up towards the brighter
part of the water column, profiting the algae and thereafter the mussels.
Mussels are farmed for various purposes (Figure 18). Mussels from the Skagerrak and
Kattegat are mostly sold for consumption, but investigations are in progress to ascertain
whether mussels can be used to filter out nutrients, e.g. at sewage works (Naturvårdsverket
2009). However, the sedimentation of organic material from faeces below a mussel
farm will also in many cases lead to bottom water hypoxia (Stadmark and Conley 2011).
70 Ecosystem Services