Welfare and Health in Danish Organic Trout Farming

Trout farming and in particular organic trout farms are critically challenged by relatively high skin/gill infections caused by various pathogens, especially the parasite Costia (Ichthyobodo necator), which is ultimately lethal for fry/smaller fish. Due to new organic regulations requesting also fry to be 100% organic, this in turn compromises supply of organic fry as basic for future production of organic trout. In addition, a Rickettsiales-like bacterium causes Red Mark Syndrome (RMS) with large red patches in the skin, which results in downgrading/rejection of up to 30% of the fish at slaughter. Treatment by use of antibiotics/ auxiliary compounds is only possible to a limited extent in organic trout production. Hence, solutions to prevent and/or treat Costia and RMS are urgently needed, not only to secure production of organic rainbow trout in Denmark, but also enable a larger and more cost efficient production with high animal welfare and minimal environmental impact. ShelterFish will focus on solutions addressing the interactions between fish - pathogens – farming environment and water quality; including 1) Test of artificial shelters (shade) to enrich environmental conditions; 2) Test of biological herb extracts and a new bacterial surfactant to treat gill/skin parasite infections; 3) Test of induced immunity to fight Red Mark Syndrome (RMS) and 4) Test of tools to reduce organic matter load in organic trout farms and hereby improve water quality, fish health/welfare. Organic trout production is following the common EU regulations for organic aquaculture, where fish welfare has high focus