Project on sustainable aquaculture and fishery management
Mussel (Mytilus
edulis) is a very important commercial seafood and one of the most
cultivated and fished bivalves in Europe. At the same time, mussels are a
keystone species in our ecosystems providing regulating services by filtrating
the water, providing habitat that sustains biodiversity, and contributing to
nutrient cycling. In Denmark, mussels constitute an important ecosystem
component as well as source of income in rural areas. More than 96% of the
fished mussel in Europe come from Denmark and 90% of Danish mussels comes from
wild stocks, where they are fished by dredging, otherwiseare cultivated in suspended
or on-bottom plots in coastal areas.
On-bottom
culture consists of transferring small mussels (mussel seeds) from a wild
source and to a licenced area for on growth. Alternatively, mussel seeds can be
captured on spat collectors, which can also be relayed to licenced areas. In
Denmark, on-bottom culture began less than 20 years ago and is principally
located in the Limfjorden. The Limfjorden is the largest estuary in Denmark, hosting
different commercial and leisure activities, as well as protected areas and
nature reserves. The main aims of bottom culture are to secure a stable source
of mussels for the fishery by by transplanting mussels from oxygen-depleted
areas to more favourable areas in order to prevent mortality, and reduce the dredging
impact from fished areas.
Mussel on-bottom
culture is facing several challenges, ranging from site selection, licencing,
seed supply, oxygen depletion, predation (mainly starfish) and relative biomass
production. The relative biomass production (RBP) is the ratio between the quantity
of harvested mussels mussels seeded. In the Dutch Wadden Sea, RBP is for
instance ranging between 1.5 to 2.5 and can reach a maximum of 6, while in
other places such as Ireland, it has been up to 7. Preliminary study of the
historical data of on-bottom culture in Denmark estimated that the RBP was
below 1, indicating a loss for the industry. In a currently running project, KulturMus (Development of new sustainable
methods in the mussel fishery), involving the fishery industry, special
emphasis on strategies to improve RBP are studied. They include site selection,
substratum, optimisation of relay density and direction, interaction with
environmental factors, biodiversity, and predation prevention. This project
will provide the student the opportunity to interact with scientist at DTU Aqua
and the fishery industry based in Nykøbing Mors to evaluate historical and
current RBP data of on-bottom culture in the Limfjorden and compare RPB trends
with environmental factors, culture practice, and seed origin. The outputs from
this project will contribute to the sustainable development of the mussel
industry.
