Identify useful variables and assemble metadata

Subtask Description:
Economic and social component formulation.

Action points of the implementation:

The Limfjord, Denmark

Policy Issue:
Sustainable mussel production in the Limfjord

Human Activities:
Mussel fishery, mussel aqua culture, agriculture, urban and industrial activity, recreational finfish fishery, tourism.

General Information:
In the early 1990s a regime shift took place in the area, and there was a transition from a demersal fishery to a mussel fishery. Eutrophication, caused by nitrogen and phosphate loadings, is still causing periodical hypoxia. The hypoxia sometimes results in large-scale mussel death and in Harmful Algal Blooms which lead to periodic bans on the commercial sale of the product. In 2006 the mussel landings fell to exceptionally low level and there is high risk of a total collapse of the mussel production. Mussel culture in lines was introduced to the area to replace the fishing activity, but this new venture is not economically viable. The main stakeholder concerns are connected to the impacts of hypoxia, the mussel fishery and the lack of finfish, and an understanding of their ecosystem functioning.

Example of Implementation:
(Regarded as socio-economic)
The economic model components run at a time step of one week. This is to comply with the weekly based management of the mussel production (harvest and fishery). Feedback to the ecological model component, in the form of lost mussel biomass, will be adjusted to link to the time step of one month (< 1).

Mussel aquaculture.
Mathematical model:


Gross growth of line mussel stock [ug C m -2 month -1]:


This gross growth function G is a rough approximation of mussel growth and will be deleted once the ecological and economic sub models are linked.

Mortality rate [month -1]:


Note: The functional relationship between labour (L) and mortality (M) needs to be established empirically. This requires information about how the moving of lines etc. prevents the mussels from dying.

Net growth of mussel stock [ug C m -2 month -1]:

dS/dt = G – M*S

Production function/harvested amount of line mussels [kg C m -2 production cycle -1]:

Quality of harvested line mussels [no dim]:


Note: The functional relationship between labour (L) and quality (Q) needs to be established empirically

Aquaculture revenue [DKK production cycle -1]:

The functional relationship between quality (Q) and price (P) needs to be established empirically. It is temporarily assumed to be linear.

Aquaculture cost [DKK/growth season]:


C = w L + c o

Aquaculture profit [DKK/growth season]:

External costs due to HAB events (opportunity costs) [DKK production cycle-1]

n = HAB events pr. production cycle

Contact: Eva Roth,