WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2024 23 (CONTINUED ON PAGE 24) farms based on the Model Trout Farm concept — and often achieved by merging smaller farms. By reducing/eliminating the use of water from streams and applying cost-efficient recirculation technology (sludge cones, drum filters, biofilters, and constructed wetlands) the farms managed to substantially reduce nutrient discharge and environmental impact15. Monitoring of eight farms over a two-year period demonstrated that increased production as well as reduced environmental impact could be achieved simultaneously. Through that, farmers succeeded in getting the law that de facto had stopped all development and innovation, rewritten. At present, such farms are regulated based on their discharge of nutrients rather than their production, making innovation and technology investments feasible and financially viable. By 2021, more than 60% of the rainbow trout production in fresh water was based on the concept of Model Trout Farms and recirculation technology. Most of the larger flow-through farms have now been converted to recirculating systems and the remaining farms may be too small for rebuilding or their niche production may not be compatible with recirculation technology. In recent years, the Danish state has bought up and closed many flow-through farms as a measure to comply with the requirements in the EU Water Framework Directive. Marine Fish Farming in Net Pens Four vertically integrated companies dominate the Danish net pen farming sub-sector. Their production of large rainbow trout starts from eggs taken from hatcheries. When the fry reach 10 grams, they are transported to land-based, recirculating smolt farms and grown for 12 to 18 months. In the early spring the smolts are transported to large net cages in the sea and harvested before winter. The fish is mainly exported as raw material to produce a wide range of value-added products, e.g. fillets, steaks, portions, grilled, marinated, hot smoked or ready dishes. In the case of mature trout, the roe is extracted and used for making salted roe (‘sujiko’) or various caviar products. The production of fish and roe at the 19 farms has been quite static in the period 2017 – 2022, with annual averages reaching some 11,400 tonnes of fish and 790 tonnes of roe. The value of the roe accounts for approximately 28% of the total gross output. Marine fish farming has by far been the most profitable sub-sector over the period 20172022 with operating margins reaching 16% compared to 6% for all farms, and it accounts for some 80% of the total net profits in the period16. The demand outlook for the sub-sectors products is very positive but the production/supply outlook is challenged by the current Danish strategy and the political and public discussion on ways ahead. Part of this discussion relates to compliance to the EU Habitat Directive/Natura 2000 protected areas. The Maritime Spatial Plan designates development zones for existing farms and applications for the establishment of new farms pending when preparing the Plan, while no zones have been designated to completely new applications. The administrative procedure for applications is progressing quite slowly and no new farms have yet been approved. The supply outlook for the sub-sector thus mainly depends on the outcome of the ongoing legal and administrative processes and future policy decisions on net pen farming. Such decisions might include necessary considerations regarding sustainability and the carbon footprint of human food supply. PHOTO 4. Danish Model Trout Farm. Photo courtesy of Per Bovbjerg Pedersen. PHOTO 5. Skagen salmon when under construction. PHOTO 3. A Danish Model Trout Farm combining intensive production with constructed wetlands to comply with discharge requirements. Courtesy DAPO.
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