are used on fish farms in Norway and to a lesser extent in Scotland, Shetland and Ireland. Their potential has not been researched in other fish farming regions, such as Pacific and Atlantic Canada or Chile. Husbandry Good husbandry techniques include fallowing, removal of dead and sick fish, prevention of net fouling, etc. Bay management plans are in place in most fish farming regions to keep sea lice below a level that could lead to health concerns on the farm or affect wild fish in surrounding waters. These include separation of year classes, counting and recording of sea lice on a prescribed basis, use of parasiticides when sea lice counts increase, and monitoring for resistance to parasiticides. Salmon breeding Early findings suggested genetic variation in the susceptibility of Atlantic salmon to Caligus elongatus. Research then began to identify trait markers, and recent studies have shown that susceptibility of Atlantic salmon to L. salmonis can be identified to specific families and that there is a link between MHC Class II and susceptibility to lice. In October 2012, the grocery chain Sobeys pulled whole Atlantic salmon from 84 store locations in the Canadian Maritimes after concerns were raised over sea lice. In 2017, salmon prices in Norway increased by 15% over a 3-month period because of a sea lice outbreak. Treatments Freshwater Freshwater is sometimes adequate to kill the sea lice and as salmon eventually swim in fresh water, they are not harmed. Drugs and vaccines The range of therapeutants for farmed fish was limited, often due to regulatory processing limitations. All drugs used have been assessed for environmental impact and risks. The parasiticides are classified into bath and in-feed treatments as follows: Bath treatments There are both advantages and disadvantages to using bath treatments. Bath treatments are more difficult and need more manpower to administer, requiring skirts or tarpaulins to be placed around the cages to contain the drug. Prevention of reinfection is a challenge since it is practically impossible to treat an entire bay in a short time period. Since the volume of water is imprecise, the required concentration is not guaranteed. Crowding of fish to reduce the volume of drug can also stress the fish. Recent use of well-boats containing the drugs has reduced both the concentration and environmental concerns, although transferring fish to the well boat and back to the cage can be stressful. The major advantage to