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fwd: Re: Supplementing Live BBS with Vitamins


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From: lund at umbi_umd.edu (Eric Lund), on 10/28/97 4:17 PM:
Re:  Enriching Artemia by feeding them marine oils.

Harry Specht wrote:

>Thanks for your efforts, Bill. The article was most interesting. It is
>apparent, however, one must raise adult brine shrimp to  utilize this
>technology and most of us employ only the newly hatched brine shrimp so I
>doubt it will help us very much.

Not so.  You can do this at home in your own fishroom using newly hatched
artemia if you want to.

My current research interests involve the dietary fatty acid requirements
of marine and freshwater fish, so I'll take a couple of minutes to
elaborate on this subject and how it may relate to keeping killies.

Briefly,  saltwater fish all require a fatty acid that is common in marine
fish oils called DHA (docosahexanoic acid) in their diet.  They cannot make
it from precursers, so it must be present in their food.  Freshwater fish
have a limited ability to make DHA from a particular precurser fatty acid
of the omega-3 variety (linolenic acid), but they too can grow and
reproduce well on a diet that includes DHA.

Brine shrimp are a great food for all small carnivorous fish, but they
contain virtually no DHA.  Marine fish larvae fed only Artemia exhibit mass
mortality a few days after they start feeding.  Aquaculture operations get
around this problem by adding an emulsion of phospholipids rich in DHA to
newly hatched artemia.  The artemia eat the emulsion (more of it also
sticks to the outside of their bodies).  The artemia are then fed to the
fish or can then be kept   refridgerated for up to 3 days.  The most
commonly used emulsion is called *Selco* and should be available at larger
aquarium shops.  You CAN do this at home.  These techniques are commonly
used by aquarists who breed marine fish.

What is the value of this to killie keepers?  Killies are freshwater fish
and thus have some capacity to produce DHA themselves.  In fact, as part of
an unpublished experiment I have raised and bred 2 generations of N.
guentheri on a diet consisting of nothing but artemia nauplii (no Selco
added).  So, with at least some killies dietary enrichment of artemia is
not necessary.  I do believe, however, that for some delicate killies that
experience high mortalities before sexing out that enriching artemia may be
of some benefit.  Another tactic worth trying is to feed enriched artemia
to the adults for several weeks prior to breeding them.  In other species,
fish eggs with low levels of DHA generally have poorer survivorship to
first feeding than eggs that are rich in DHA. Giving females a diet high in
DHA allows then to put more DHA into their eggs.  As you all know, weak and
feable killie fry can be the result of several factors including
inbreeding, bad water conditions and improper incubation conditions, but
poor parental nutrition may play a role as well.

If anyone wants more information on this subject they can contact me via
private email.

Regards,

Eric Lund

lund at umbi_umd.edu