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Dear Mareike,I`m working on gut contents of mudskippers in a tropical area: in my case I decided not to keep the stomach in ice for more that a couple of days, and fix them asap in formalin or etoh. I kept some fish for 3-4 weeks in a freezer (~ - 18 degrees C), and most of the stomach contents were spoiled (becoming a mucillaginous mass, much more difficult to identify than the samples fixed after few days in etoh or formalin...).
Moreover, I euthanise the fish immediately in the field by putting them in a slurry ice instead of just ice: temperature is lower and the digestive process can be stopped earlier. Anyway, maybe this is not your problem, if you have a good freezer on board.
Hope this could be of some help!All the best,
Laura
>----Messaggio originale----
>Da: [log in to unmask]
>Data: 22/11/2011 13.35
>A: <[log in to unmask]>
>Ogg: Re: Herring stomach analysis
>
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> REPLIES WILL BE SENT TO THE FISH-SCI LIST
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>
>Thank you!
>
>Some fish were frozen directly on board, for others I could take the stomach out on board and then freeze it directly after. And that is now about 4 weeks ago, but samples stayed frozen for the whole period.
>
>We will look at stable isotopes of some individuals as well, but it would be too expensive to analyze all the samples.
>
>Mareike
>
>
>
>-------- Original-Nachricht --------
>> Datum: Tue, 22 Nov 2011 12:13:46 +0000
>> Von: Chris Harrod <[log in to unmask]>
>> An: [log in to unmask]
>> Betreff: Re: [FISH-SCI] Herring stomach analysis
>
>> As Zach said, freshness is indeed the key to reliable SCA.
>>
>> If you can't get the fish straight onto/into ice, an alternative is to
>> inject a preservative into the stomach/body cavity. People have used formalin
>> in the past, but you might have fun getting it past the Health and Safety
>> people.
>>
>> If you really want to know whats in the gloop, you could take a DNA based
>> approach. Alternatively, use isotopes on the fish?
>>
>> Good luck
>> Chris
>>
>> ________________________________
>> From: Zachary Whitener
>> Sent: Tue, Nov 22, 2011 8:36 AM
>> To: [log in to unmask]
>> CC:
>> Subject: Re: Herring stomach analysis
>>
>> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
>> REPLIES WILL BE SENT TO THE FISH-SCI LIST
>> <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <><
>>
>> Good morning,
>>
>> How are you getting these herring? How long after capture do they get to
>> you? I have worked with both Atlantic herring and Alewives and have
>> learned that freshness is paramount since digestion continues even after
>> the fish is dead. The best scenarios are to cut them from the fish and
>> get
>> them either on ice or in ethanol (the better option) as soon as possible
>> to
>> halt further digestion. The prey items are so small that any further
>> digestion renders identification almost impossible. I hope this helps.
>>
>> Zach Whitener
>>
>> On Tue, Nov 22, 2011 at 7:15 AM, Mareike Volkenandt
>> <[log in to unmask]>wrote:
>>
>> > ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
>> > REPLIES WILL BE SENT TO THE FISH-SCI LIST
>> > <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <><
>> >
>> > Hello everyone!
>> >
>> > I just started with my PhD-thesis. Between other things, I would like to
>> > look at the stomach content of Herring from different size classes. It's
>> > the
>> > first time, that I'm doing such an analysis. We weight the stomachs and
>> > visually estimate level of fullness. We also want to identify prey
>> species.
>> > In a test run, I had difficulties recognizing any prey species or groups
>> in
>> > the stomach. It was only a big, brownish, digested mix of something...
>> >
>> > Do you have any advise on a best method or way of handling?
>> > Could you recommend me any identification keys or literature references
>> > that
>> > were helpful for your work?
>> >
>> > Thank you in advance.
>> >
>> > Mareike
>> >
>> >
>> >
>> -------------------------------------------------------------------------------------------
>> > Mareike Volkenandt
>> > MARES Phd student
>> >
>> > Marine Biodiversity Research Group
>> > Marine & Freshwater Research Center
>> > Galway - Mayo Institute of Technology
>> > Dublin Rd
>> > Galway, Ireland
>> >
>> > Phone: +353(0)9174 2502
>> > [log in to unmask]
>> >
>> > About MARES: http://www.mares-eu.org/
>> >
>> >
>> ------------------------------------------------------------------------------------------
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