Objectives
- To optimize the production of a mussel mitigation farm.
- To estimate the growth potential of mussels at low salinities.
- To minimize risk of failure due to ice cover, predation and exposure.
- To evaluate the feasibility of using multi-trophic aquaculture for mitigation.
Tasks
Optimize production of the blue mussels
In order to increase biomass on long-line farms in the Limfjorden (Denmark) and Tjärnö (Sweden), different configurations of e.g. density, total length of droppers, buoys of different sizes will be tested together with different settling material, e.g. the X-plora system, vs. settling bands in either one or several of the study sites. In Horsens Fjord (Denmark), different configurations of tube and net systems (Smart Farm) will be tested with focus on net type. Production volume and labour effort will be monitored continuously as a function of treatments.
Estimation of mussel growth at low salinities
The production potential of mussels in Greifswald Bay with low salinities will be estimated in a new farm of 1 ha using long-lines. The prevailing Mytilus subspecies will be identified on different stations in order to identify the subspecies with the highest growth potential for mussel farming. Environmental data (salinity, temperature, Chl. a, nutrients, bottom oxygen) and mussel data (biomass, shell lengths, spawning, NP content) will be collected regularly near the farm and used to estimate the production capacity and the best time for harvest.
The new information will also be used to re-calibrate the DEB model and provide necessary background-data for locating potential new regions for mussel farming along the south-Baltic coast in WP5.
The perspectives of using mussel mitigation cultures in this area with low salinity will be evaluated based on the new data.
Reduce impact of ice cover and predation on blue mussel production
In order to reduce the damage from ice cover, different techniques like deepen the ropes (long-line farms) below the ice and use of different buoys will be analysed, optimized and implemented in local farms.
Different systems to prevent predation by eiders will be tested in Horsens fjord and Tjärnö with focus on blocking the entrance to the production units using nets but also use of laser-lights, live falcons to scare the birds away as well as “bird of prey kites” will be tested and demonstrated on a training course for mussel farmers.
Evaluation of the potential for using multi-trophic aquacultures (MTA)
MTA are suggested to reduce costs and to increase the compensation of nutrients released by fish cultures. However, a close integration of the MTA is often not possible due to high current velocities transporting nutrients to other parts of the water basin and because mussel- and algae farms are less suited to off-shore conditions. Thus, site-selections of the mussel and macro-algae farms are important to obtain an efficient mitigation effect on basin scale. The potential of MTA in each study sites will be evaluated using existing knowledge and modelling, and recommendations of farm layout will be provided.
Partners involved
- Leibniz Institute for Baltic Sea Research
- Technical University of Denmark
- Aarhus University
- University of Gothenburg
- Hjarnøe Havbrug A/S