Fraser River sockeye salmon: data synthesis and cumulative impacts

Levy: It will go ahead in January. It will be timed to be ready for the aquaculture part of thehearings. The implications for us are that we will have to re-open the cumulative effectsanalysis.Routledge: It’s correct that there is no evidence re sea lice and Fraser sockeye but there arestudies on impacts in Atlantic salmon, which are relatively large, and they can causemortality, so I wouldn’t want to discount it.Routledge: Is there any evidence of vectors for disease to consider?Kent: You can show in lab studies that Lep can jump from adult fish. Some pathogens forexample are transmitted via leeches but can also transfer through the water. Could sea lice betransmitting disease? In freshwater, there have been increases in snail-borne disease due toincreasing numbers of snails. There is the whirling disease story in the US Rockies, linked toland use and eutrophication. Arthropods as vectors is also worthy of addressing.Reynolds: A recent paper showed sea lice do jump from host to host in the wild. Male Lepjumped from pink to coho smolts.Peterman: Re recommendations 3 and 4, a problem with pathogens is the need for a rigoroussurvey program over a long period to see something interesting. It would be useful for theCommission to know how you would recommend dealing with this given limited dollars.Kent: One concern is epizootics and outbreaks of new pathogens. The other one (work was donewith coho parasite impacts on over-winter survival – see the Crofton slide) that can have asignificant impact on populations is that at a certain level you get a dramatic increase inpathogen-associated mortality. So it doesn’t have to be a brand new or highly-lethalpathogen. It could be a shift in the severity of the pathogen level. So if you are collecting fishsamples anyway, why not collect disease information as well so that you have informationover time. You can do more sophisticated models that also look at things like the relationshipbetween parasite burden and size.Peterman: To get the data for that graph, you need a well-designed consistent program. Theseprograms may be opportunistic, which may not be good enough.English: Juveniles can pick up Parvicapsula in freshwater, then migrate out to the ocean. It isreasonable to assume that the Parvicapsula is continuing to impact and potentially killingthem or attacking them as returning adults.Kent: Parvicapsula is similar to another estuarine parasite in a US river that infected fish goingout and in. There is the question of whether there is a heavier load, so it’s not just a questionof whether they are present or absent. Abundance is driven by temperature and most fishleave before temperatures are high enough, but it could be a shift where they are now out ofwhack.Martin: Given temperature and geographic changes in survival for a large number of stocks, doesthat eliminate or point to some of the parasites listed today?Kent: There is the example of Parvicapsula (but I’m not saying parasites are a major driver ofmortality).Martin: It could be one contributing factor.43