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Index of Subjects "...Salmon escapees should not be a problem, at least genetically, because they > are using triploid fish. Does this stop interbreeding with wild stocks > because the triploid fish do not mature? Does this even prevent genetic > mixing with native fish?" Good question which I pursued a bit. Triploidly is apparently a technique that is being investigated but has not yet been applied to the industry: From a 2008 documnent: "The use of sterile salmon is a measure that should be carefully appraised, considering the positive effects it could have on reducing direct genetic effects of farmed salmon on wild salmon populations. It may also reduce ecological effects. However, it is unlikely to greatly reduce threats from the transmission of diseases and parasites. The most effective method of sterilising Atlantic salmon is high pressure induction of triploidy in newly fertilised eggs. Triploids have a number of disadvantages in commercial aquaculture, but results from different studies vary with regards to triploid growth, survival and the occurrence of deformities. Triploidy is a procedure that can be applied to different stocks which, as diploids, are likely to exhibit different morphological, behavioural and performance characteristics. It is therefore unlikely that the characteristics of different triploid stocks will be the same. Use of triploid (i.e. sterile) salmon in commercial farming would require research and development to determine optimum rearing conditions and boost triploid disease resistance. Ecological interactions of farmed sterile fish with wild fish must be critically evaluated before large-scale use of sterile fish can be encouraged." Source: Incidence and impacts of escaped farmed Atlantic salmon Salmo salar in nature Eva B. Thorstad et al. Report from the Technical Working Group on Escapes of the Salmon Aquaculture Dialogue 2008 ftp://ftp.fao.org/fi/document/aquaculture/aq2008_09/root/aj272e.pdf More on the genetics and crossbreeding in Genetic consequences of interbreeding between farmed and wild Atlantic salmon: insights from the transcriptome. CHRISTIAN ROBERGE et al. Molecular Ecology (2008) 17, 314?324 doi: 10.1111/j.1365-294X.2007.03438.x http://www.bio.ulaval.ca/cirsa/Publications/Roberge_MEC_08.pdf Abstract Large annual escapees of farmed Atlantic salmon enhance the risk of extinction of wild populations through genetic and ecological interactions. Recently, we documented evolutionary change in gene transcription between farmed and wild Atlantic salmon after only five generations of artificial selection. While differences for most quantitative traits are expected to gradually dilute through repeated backcrossing to wild populations, the genetic basis of gene transcription has been shown to be largely nonadditive and hybrid crosses may display unexpected inheritance patterns. This makes it difficult to predict to what extent interbreeding between farmed and wild individuals will change the genetic makeup of wild salmon populations. Here, we compare the genome-wide gene transcription profiles of Norwegian wild salmon to that of a second generation hybrid cross [backcross: (Farmed X Wild) X Wild]. Over 6% (298, q-value < 0.01) of the detected genes exhibited highly significantly different transcription levels, and the range and average magnitude of those differences was strikingly higher than previously described between pure farmed and wild strains. Most differences appear to result from nonadditive gene interactions. These results suggest that interbreeding of fugitive farmed salmon and wild individuals could substantially modify the genetic control of gene transcription in natural populations exposed to high migration from fish farms, resulting in potentially detrimental effects on the survival of these populations. This further supports the idea that measures to considerably reduce the number of escaped farmed salmon and their reproduction in the wild are urgently needed Quoting Elizabeth Doull <edoull@ns.sympatico.ca>: > > ----- Original Message ----- > From: Nancy Dowd > To: naturens@chebucto.ns.ca > Sent: Monday, November 05, 2012 8:17 AM > Subject: Re: [NatureNS] re West coast:Fw: Farmed Salmon > > > A library patron I was talking to a few Saturdays ago suggested farmed > salmon escapees should not be a problem, at least genetically, because they > are using triploid fish. Does this stop interbreeding with wild stocks > because the triploid fish do not mature? Does this even prevent genetic > mixing with native fish? > > > Nancy > > > -------------------------------------------------------------------------------- > From: David & Alison Webster <dwebster@glinx.com> > To: naturens@chebucto.ns.ca > Sent: Sunday, November 4, 2012 1:08:28 PM > Subject: Re: [NatureNS] re West coast:Fw: Farmed Salmon > > > Thanks Dave P. & John. Good to learn about an objective study & hear from > the voice of experience. Start small is sound advice when doing something > new. > Perhaps the underlying problem is that both the wild fishery and salmon > farming can be too darn profitable ! A friend of Alison's from the Shetland > Islands lamented about 10 years ago that it was difficult to keep young men > in school there when they can earn enough in the fishery (no need for high > school) to retire by 30 or so. > > Yt, DW > >
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