[NatureNS] Farmed Salmon.. interbreeding with wild Salmon?

Date: Mon, 05 Nov 2012 20:47:02 -0400
From: David Patriquin <patriqui@dal.ca>
To: naturens@chebucto.ns.ca, Elizabeth Doull <edoull@ns.sympatico.ca>
References: <01585F09E4154870BF686560355894EB@D58WQPH1>
User-Agent: Internet Messaging Program (IMP) H3 (4.3.4)
Precedence: bulk
Return-Path: <naturens-mml-owner@chebucto.ns.ca>
Original-Recipient: rfc822;"| (cd /csuite/info/Environment/FNSN/MList; /csuite/lib/arch2html)"

next message in archive
no next message in thread
previous message in archive
previous message in thread
Index of Subjects

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
>
>




next message in archive
no next message in thread
previous message in archive
previous message in thread
Index of Subjects