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Re: Vlue of artemia nauplii



>From: Raj <ggrk at blr_vsnl.net.in>
>Subject: OSI Brine shrimp eggs
>
>I have a large can of brine shrimp eggs by OSI which doesn't hatch..
>other makes hatch under the same conditions. There is no date stamp
>on the can, I read somewhere that these eggs hatch better if they >are 
>older.
>So far never had a response from OSI, anyone know how to hatch these?
>I de-shell them and use sometimes but I rather have them live..

Hi Ray,
As far as my knowledge goes, OSI harvested its Artemia cysts mainly from the 
Great Salt Lake in Utah in the past so we can carefully assume that you have 
bought Artemia franciscana GSL cysts. It speak for itself that you should 
not take my word for it and you should try to verify this with the original 
manufacturer. GSL-cysts used to have decent hatching characteristics but a 
medium shell life of about a year or so. Did you buy the can in India? A 
potential source of problems might be the storing of the cysts then, due to 
the high temperatures in your country.

Personally, I do not believe that the cysts will hatch better when they are 
older. Initially this is true yes, as the cysts need to break their diapause 
(= state of severely suspended metabolism). One can see the hatching 
percentage increasing slowly from the moment the cysts are harvested from 
the field and stored. This diapause breaking is mostly achieved by cold 
storage and proprietary processing techniques of the cyst processor. Once 
cysts have broken diapause and have been processed, they should be stored 
correctly (i.e. in a dry and cool place) or used soon afterwards. Handling 
procedures by distributors and retailers are always a hot topic in our 
industry due to (economic) constrains placed on the handling of cysts  that 
is the way it is and there is not much one can do about it.

>>3. There are way more than the fish can eat in a few feedings. How >> do I 
>>keep
>>the rest alive in the meantime?

>Transfer (after rinsing) to fresh icy weak salt water in a very >shallow 
>tray in the refrigerator. You can delay that first molt for a day or so, I 
>think.

That is indeed the best solution. Fridge temperatures will severely depress 
nauplii metabolism and retard bacterial growth. On the other side I always 
advise against putting live foods in the same fridge as where you store your 
groceries just to be on the safe side.

>They can be fed green water and rotifers and foods prepared for >brine 
>shrimp, but they increase in size and are soon no longer an >optimal size 
>for smaller fry.

Careful, green water is a very broad term. One must check that the culture 
contains unicellular green algae and diatoms, otherwise the algae or too big 
to be ingested by the nauplii and/or the algae might clog up the developing 
thoracopods on the nauplii.

Rotifers are too big to be eaten even by adult brine shrimp and are superior 
feeders compared to brine shrimp, i.e. they clear the water of algae before 
the brine shrimp do.

What is the value of Artemia nauplii?
Their nutritional profile indeed is so-so, but what makes the nauplii stand 
out is their wriggling way of swimming which acts as a powerful feeding 
response for fish fry. Another overlooked fact is that fish fry are thought 
of to make advantage of the nauplius' digestive enzymes as most fish fry 
have a very weak digestive system when being so young.

Freezing: is the other viable alternative. Follow Wright's guidelines and 
pre-chill the plastic bags and tap water. The speed of freezing is the key 
to success.

>That's my $0.02. If I have it wrong, I trust the pros to jump in and >set 
>me straight.

That won't be necessary as nearly always, you hit the nail on the head.

Regards,
Steve Geerts
Biologist San Francisco Bay Brand
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