SURVIVAL IN PENAEUS HATCHERIES
From: getah <getah@yahoo.com>
To: shrimp@yahoogroups.com
I need help from experts in this mailing list. Our
hatchery had
successfully produced monodon PLs and stylirostris PLs. This year we
try to produce vannamei PLs, it has been 3 months now and the production is
very low. From nauplii to harvest time, the survival
rate is only 10% at best. Counting to the tanks that were flushed,
the total SR (from total nauplii to total harvested) is probably in 2-
3%.
The trouble is most of the nauplii could not get past zoea/mysis
stage.
Is producing vannamei PLs different from other
species? If it does, can
you teach me how? Is there a proven method to raise the SR effectively?
Getah
e-mail: getah@yahoo.com
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COMMENTS 1:
We have the same problems in P.monodon Zoea/Mysis in
certain batches, while at the same time some batches have normal survival
rates between 50 to 70%. In our case, perfectly normal and healthy
Mysis suddenly stop feeding, become weak and fail to become Post
Larvae.
This is a new problem which started only this year.
Anil Ghanekar
e-mail: anilghanekar@yahoo.com
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COMMENTS 2:
That sounds similar to zoea syndrome to me.
In zoea syndrome, larvae stop feeding at zoea 2 stage and spend like 4-5
days without molting to the next stage. Larvae don’t eat, have no feces,
and are totally white and without lipids. Mortalities can go up to 80-90%.
It's caused by a vibrio.
Some of the prevention methods used in Ecuador are: reducing the stocking
period of the hatchery to no more than 3 days, probiotics and strong
asepsis.
Some of the treatments used (mostly with not very good results) are
antibiotics, and sacrifice.
Fabrizio Marcillo
e-mail: barcillo@gu.pro.ec
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COMMENTS 3:
Are you 100% sure that the zoea syndrome is caused by
vibrio? So far,
I have read and heard that it is still a syndrome because no conclusive
results have been found to point out vibrio as the cause.
e-mail:
postlarmar@geo.net.co
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COMMENTS 4:
What do you mean by "reducing the stocking
period in hatchery to no
more than 3 days"?
Getah
e-mail: getah@yahoo.com
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COMMENTS 5:
I agree with Fabrizio about some kind of Vibrio is
the causative agent of Zoea Syndrome. At the time of this Z2 syndrome
outbreak, I was working for CENAIM, and later they found a Vibrio isolate
from disease zoeas. They re-infect healthy zoeas with this isolate,
but never could plate bacteria on standard growth agar or isolation media.
They run a genetic assay and found some similarities with pathogenic vibrios
like Vibrio vulnificus.
The guy who was involved in this research is Dr. Marcelo Muñoz.
Gabriel Rivera
e-mail: griveralo@yahoo.com
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COMMENTS 6:
Do you have any hard data to indicate vibrios are
indeed the culprit? I
am still operating on the assumption that micro-bacteria are the bad
guys.....what you suggest is still the right strategy: stock in a maximum
of 5 days....but I am curious what further work has been done on
understanding the root cause.
e-mail:
jtabrah@oceanicinstitute.org
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COMMENTS 7:
Sorry, I should have said "there's some evidence
that it's caused by a
vibrio" instead of "It's caused by a vibrio".
Some of the evidence is what Gabriel said about the research in Cenaim and
also a thesis: "Intriago W.-1998.- Problemas de Aislamiento y
caracterización de bacterias asociadas al síndrome de Zoea II y demostración
experimental de su patogenicidad".
To respond to your question: No, I'm not 100% sure. And wouldn't be
surprised if there where several similar "diseases" that could be
catalogued as Zoea syndrome.
Last year while preparing a class I made an informal poll of some hatcheries
in Ecuador, and all of them used the 3 or 4 day stocking strategy. This is
to limit the maximum amount of days in which you stock all your hatchery
to less than 4 days after the dry out, because all said if they didn't
stock in that amount of time they had problems in the last tanks to be
stocked.
The reason appears to be a contamination from the oldest tanks to the
youngest.
Most of them had used antibiotics at some point with bad results, I didn't
ask which ones or which doses, and most had stopped using them for this
purpose.
I repeat this is far from hard data, but gives an idea of what some people
are doing.
e-mail: barcillo@gu.pro.ec