Interesting topic for me
I contacted CSIRO in Hobart - Bob Ward - expert regarding DNA fish issues
and he commented
Quote
I'd like to hear more about the UK test. Seems very odd.
The test we (and most other labs use) is a mitochondrial DNA test - and
there's no easy way this can show two species as it is inherited only from
mum and is a non-recombining molecule. I have never heard of an individual
having mtDNA from more than one species and don't see how it could happen.
If it's a real documented result, not just an unattributable anecdote, and
if it was a mtDNA test, it could indicate contamination of the sample
somewhere, somehow.
If it was a nuclear DNA test (somewhat unlikely), then past hybridization
(if it occurred) would make it possible to detect two species in a single
tissue sample. But not for a mtDNA test. Although for a mtDNA test, past
hybridization would make it possible to show the DNA of either past parental
species in a descendant (but not both).
Unquote
Hope this helps
Cheers roy
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On Behalf
Of Surefish Bellingham
Sent: Thursday, 18 October 2007 8:46 AM
To: Jon McGraw; 'John Sackton'; 'Richard Chivers'
Cc: 'seafood'
Subject: Re: Cod and Alaska pollack
Cross contamination is what I thought when I read the original inquiry.
I do lot inspections on H&G cod and pollock. It isn't uncommon to find a
pollock mixed in with the cod. In this situation pollock isn't what the
fishing boat is targeting, but at the same time they separate the pollock
and also do H&G pollock. The fish look somewhat similar, but a trained eye
can distinguish them. I can't remember ever seeing cod mistakenly mixed in
with the pollock though...
Mark Neely
Surefish
----- Original Message -----
From: "Jon McGraw" <JonMcGraw@seafreeze.com>
To: "'John Sackton'" <jsackton@seafood.com>; "'Richard Chivers'"
<richard@fishonline.co.uk>
Cc: "'seafood'" <seafood@ucdavis.edu>
Sent: Wednesday, October 17, 2007 1:12 PM
Subject: RE: Cod and Alaska pollack
> Bingo, John's spot on IMHO.
>
> Jon McGraw
> Seafreeze
>
> -----Original Message-----
> From: John Sackton [mailto:jsackton@seafood.com]
> Sent: Wednesday, October 17, 2007 1:01 PM
> To: Richard Chivers
> Cc: seafood
> Subject: Re: Cod and Alaska pollack
>
> Why would this most likely not be an example of cross contamination.
> Many factory trawlers fish for both cod and pollock. A fillet
> inspection line, for example, could easily be a site of cross
> contamination between the two species.
>
> Alternatively, this could have been a thawed fillet from frozen H&G
> cod, and the same factory could also be producing Alaska pollock
> fillets. The entire handling history of the fillet would have to be
> traced to determine where the AK pollock dna came from.
>
> If this was from a fillet block, there is a practice of using minced
> fish along with whole fillets in some blocks -- this could be another
> source, if minced pollock was used instead of minced cod.
>
> best
>
>
> John Sackton
> Seafood.com News
>
> On 10/17/07, Richard Chivers <richard@fishonline.co.uk> wrote:
>>
>>
>>
>>
>> Dear All,
>>
>>
>>
>> A sample of cod was analysed by a UK Public Analyst using a DNA
>> sequencing
>> and he found evidence of DNA of more than one species. They have
>> confirmed
>> cod, but also detected Alaskan pollack, and possibly one more species.
>> The
>> sample was just a fillet of fish, presumably cod, taken at retail.
>>
>>
>>
>> Does anyone know of cod interbreeding with Alaska Pollack. The sample
>> was
>> taken in the UK and I would normally expect this to indicate Gadus morhua
>> but it is possible that Gadus macrocephalus had sneaked in some how.
>>
>>
>>
>> Thank you in advance.
>>
>>
>>
>> Richard Chivers
>>
>> Seafood Audit International
>>
>>
>
>
> --
> John Sackton
> Seafood.com News
>
>
>
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