Sea Lice AND Salmon - Farmed And Dangerous

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On Scotland’swest coast farms,farmed salmonproduced 78 to97 percent ofall Scottish lice,and wild salmonproduced fewerthan 1 percent.Given that salmon farms can have very highlevels of sea lice infestation, that the farms areoften located on migration routes of adult andjuvenile wild salmon, that the farms’ net penspermit sea lice to disperse throughout themarine environment, that the probability ofbeing infected with sea lice—or any other disease—increaseswith proximity to, and numbersof, sea lice, it is more than likely thatfarmed salmon infect wild salmon.3. DO SEA LICE DAMAGE FARMED& WILD FISH IN THE SAME WAY?Sea lice are costly to the world’s fish farmers.They injure and kill fish, reduce growth rates,and oblige expensive control treatments. Onestudy estimated that a 20-net pen fish farmwith 10,000 salmon per pen, can lose$336,000/crop due to sea lice. [41]4. IS THE SEA LICE PROBLEMLIMITED TO BC?Sea lice do not cause problems only for thewild and farmed salmon of British Columbia.Major infestations of sea lice—both on wildand farmed salmon—have been reported everywheresalmon farms have been established. [81]Untreated infections have resulted in seriousand costly consequences. [55, 62, 63] In 1996,the total cost of treatments and of the lossesassociated with injuries and deaths caused bylice in Norway and Scotland were $33 millionand $25 million (US), respectively. [64, 65]5. CAN THE ATLANTIC ANDPACIFIC BE COMPARED?Despite the environmental differences betweenthe Atlantic and Pacific Oceans, the impacts ofsea lice outbreaks on salmon farms and onwild salmon are similar. By taking advantage ofyears of sea-lice research, we can avoid reinventingthe wheel, and can focus on deservingissues, such as how to eliminate lice impacts.BC cannot assume that the future health andbiodiversity of its wild salmon are secure. Itcould be that restoring salmon biodiversityproves impossible or at least, prohibitivelyexpensive. The sea-lice problem, here andthere, is serious now.6. ARE THERE MORE SEA LICENEAR FARMS?While sea lice occur naturally in coastal waters,studies in Norway, [59] Ireland, [66] and Scotland[67] suggest that most lice larvae originate onfarmed salmon, and that densities of larval [68]and adult [69] lice are much higher in farmsthan in the wild. Wild salmon captured nearBritishColumbiaNewBrunswickScotlandIrelandNorwayChileFIGURE 6Locations of outbreaks ofsea lice, Lepeophtheirussalmonis, on wild fish andfarmed fish in the world.Major infestations of sealice—both on wild andfarmed salmon—have beenreported everywhere salmonfarms have been established.Peter Bromley map12 Sea Lice and Salmon: Elevating the Dialogue
salmon farms carried an average of 100 liceper fish. Salmon captured away from farmscarried an average of 13 lice. [70] A recentstudy in the Broughton Archipelago found sealice were almost 9 times more abundant onjuvenile wild salmon near farms holding adultsalmon and 5 times more abundant nearfarms holding smolts, than in areas distantfrom fish farms. [110]7. HOW MANY SEA LICE EGGS CANA SALMON FARM PRODUCE?Though impossible to determine exactly howmany sea lice eggs can be produced by licefrom a single salmon farm, scientists can estimatelice egg production. Based on what isknown about lice and about the number andspecies of the fish in the farms, some 29 billionsea lice eggs may have been produced byNorwegian farmed salmon in the year 2000 —assuming that the Norwegian regulation allowinga maximum of 0.5 gravid (pregnant)female lice/fish was followed. [59] Anotherstudy on Scotland’s west coast farms foundthat farmed salmon produced 78 to 97% of allScottish lice, and that wild salmon producedfewer than 1%. Escapees from salmon farmsaccounted for the remainder. [71]Lice from farmed and wild fish look the same.Alexandra Morton photoThe BroughtonArchipelago1. WHERE IS THEBROUGHTON ARCHIPELAGO?The Broughton Archipelago is a group ofislands north of Johnstone Strait, off the northeastcoast of Vancouver Island.8. ARE THERE DIFFERENCES BETWEENLICE FROM FARMED & WILD FISH?It has been suggested that lice on farmedAtlantic salmon produce fewer eggs than liceon wild Atlantic salmon—500 eggs/brood and1000 eggs/brood respectively. [66] However,there are no visual differences between sealice found on farmed salmon and those foundon wild salmon. Also, although scientists havenot yet definitively determined whether sealice move from farmed salmon to wild salmon(or vice versa), a large body of circumstantialevidence suggests that salmon farming contributesto sea lice abundance, and negativelyaffects wild salmon. Because sea lice infestationsmore commonly occur on wild fish thathappen to be near fish farms, it seems likelythat the farms are implicated. [17]THE CENTRAL COASTFIGURE 7 Location of the Broughton Archipelago.Sea Lice and Salmon: Elevating the Dialogue13
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Page 9 and 10: diseases and parasites can and will
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