I agree with clarkii that the article is missing some information here because are we talking about fresh live fish, carcasses or both? If they were carcasses I would be interested how long they were lying around. Where they fresh (red gills), tainted (pink gills) or rotten (goo bag) carcasses? How many fish were actually sampled where these abnormalities (i.e. black eggs) were observed? How many prespawns are we talking about? Was high prespawn mortality observed at the start and continued past peak of spawn?
Generally speaking, prespawn mortality is not abnormal. It is not uncommon to have spawning success starting out poor at the start of the run, but improve as it reaches peak of spawn. Some years, you can have very high prespawn mortality right from the get-go and it never gets better and in those same years with co-migrating species spawning success can be at or above historical averages. On the first survey, if you show up and the dead recovery is as high (or higher) than the live count then that isn’t a good sign. Unfavourable migratory conditions such as high water temperatures and discharge can be present during periods of high prespawn mortality; however, generally, Fraser River conditions this year have been good from the end of July onwards.
However, a person just can’t look at some prespawns on the spawning grounds and conclude that some mysterious disease is at play. A salmon carcass lying on the stream bank can have numerous pathogens in them which can make it very difficult for fish health people to determine what caused the dead of the fish. Once adult Pacific Salmon enter freshwater the process of putrefaction and cell autolysis is underway and is greatly accelerated once it dies and is exposed to the elements. For these reasons, Fish Health people are not very enthusiastic in analyzing salmon that have been dead for an undetermined amount of time. Most times the quality of the sample won’t be really seen until the lab technician has prepared the sample for analysis through a series of steps – only to find out at the end of the process that the sample is not useful. However, they have to go through that process regardless because the quality of the sample won’t show up until the end. Analyzing fish for pathogens is not cheap. Once that money is spent to spent to prepare those samples that’s it – there is no refund. In addition, there is not many staff at Pacific Biological Station to do this work, so it is important to get the best quality samples possible from the start. Fresh, live fish are the best to sample and analyze in order to get the best results.
Alexandra Morton does not get fresh, live fish, so anything other than that can have very suspect results as we have come to learn already from her work. Her “field researchers” apparently believe that a salmon carcass should retain its red gills or it is “suspicious”. Any spot, wound or discolouration is seen as abnormal and of course – “suspicious”. Although these individuals are highly motivated, enthusiastic and love wild salmon their work is more speculation than actual science. Morton can treat those samples from the carcasses she collects with as much TLC as she would like, but in the end garbage in equals garbage out.
There’s no excuse for DFO not to be on spawning streams this fall and sending reports of abnormalities to government laboratories or documenting the scarcity of spawners.
Well, that is not entirely true. Stock Assessment staff are on the spawning grounds conducting enumeration work, but are also observing any abnormalities noticed during that work. That is part of the job. In addition, DFO’s Environmental Watch Program observes the migration biology (field and laboratory research) of Pacific Salmon and monitors environmental conditions in the Fraser River – providing inseason, scientific advice to fisheries managers on the impact of environmental conditions on Pacific Salmon survival. Although I see the authors point about having more monitoring on these smaller streams he mentions, unfortunately these days there are no funds and staff to monitor all these small creeks. If something is picked up then something would inevitably fall off the table.
Are the immune systems of chum passing fish farms weakened along with sockeye?
More speculation than fact.
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Topic: Wondering (Read 10102 times)