Sea Lice AND Salmon - Farmed And Dangerous

There is noknown ‘silverbullet’ forpermanentlystopping sea liceinfestations onfish farms.Treatment1. HOW DO SALMON FARMERS TREATFARMED SALMON FOR SEA LICE?In order to avoid costly losses, salmon farmershave developed a variety of methods to preventand treat sea lice outbreaks. Good farmmaintenance and husbandry can help preventoutbreaks, and chemicals and drugs can helptreat salmon after an outbreak occurs. There isno known ‘silver bullet’ for permanently stoppingsea lice infestations on fish farms. Mostsalmon farmers use a combination of treatments,depending on the severity of the infestationand the stage in the sea louse developmentcycle. [78]Various measures can be used either beforea sea lice outbreak, or as part of a continuousmanagement regime. They include thefollowing: [79]■ Proper site location —which maximizesthe chances that farmed salmon will behealthy by ensuring that farms are notlocated near potential sources of infection,such as salmon-bearing streams and othersalmon farms;■ Adequate tidal current —which minimizesdangers associated with accumulationof sea-lice larvae;■ Separating year classes —whichprevents smolts (i.e. the lice-free, freshwaterjuveniles) from contacting the older andalready lice-infested farm fish;■ Fallowing —which breaks the reproductivecycle of sea lice, thereby reducing the riskof outbreaks;■ Minimizing crowding —which decreaseshost density and stress, and therebyreduces infection rates;■ Good husbandry —which contributes tothe health of fish. Cleaning and caring ofnets is one example;■ Cleaner fish (wrasse) —which eatparasites carried by other fish, and feed onalgae and sessile animals, such as mussels(common on nets) are a less-expensive andnon-chemical means of controlling sea licecurrently being used on some Europeansalmon farms. [64] Unfortunately, there areno native wrasse in BC. Nor is it advisableto introduce non-native species into anyenvironment—including introducing Atlanticsalmon to the Pacific coast;■ Reactive treatments —which are usuallya chemotherapeutant given to farm fisheither in food or as a bath, after a sea-liceinfestation has occurred. Bath treatments aredifficult to administer and are not effectiveagainst all life stages of sea lice. Feed treatmentsare more effective, and farmers cantreat many cages quickly. Although dilutedby surrounding water, the chemicals usedmay affect non-target wild crustaceans andmay remain in the environment from tendays to six months. [78, 80-89] The ability ofsea lice to quickly develop resistances tochemical treatments is also a major issue.[111]2. WHAT IS FALLOWING?Just like farms on dry land, fish farms can befallowed. By taking all of the farmed salmonout of a farm and leaving it empty for oneproduction cycle (two years), the seabed mayrecover from damage caused by the farmabove it. It also breaks the cycle of sea liceand other disease infestation in that farm. Fallowingis most effective if all the farms in anentire bay or fjord are emptied, because it ismuch less likely that farms will be reinfectedby their neighbours. To be effective, fallowingmust be done in conjunction with a separationof year classes to ensure that smolts are notinfected by adult fish in the same farm.3. WHAT IS SLICE?SLICE is the commercial name for emamectinbenzoate, a chemical used to kill sea lice. Ithas mostly replaced its more costly and lesseffective predecessor, Ivermectin. [41] AlthoughSLICE is currently undergoing clinical trials inNorway, Scotland, and Chile, [78] in Canada, in16 Sea Lice and Salmon: Elevating the Dialogue