Zoea
syndrome
From:
Anil Ghanekar
To: shrimp@yahoogroups.com
Sent: September 25, 2002
QUESTION:
Many
hatcheries have reported high mortalities in
zoeal stages recently.
PCR tests show negative results for WSSV,
Higher levels of nutrition and higher densities in
Zoea have improved survival rates but the problem
still exists.
Any suggestions/solutions to this would be welcome.
e-mail:
anilghanekar@yahoo.com
***************
COMMENTS
1:
You
shouldn't have problems appearing with WSSV at larval or Zoea stages; this
worry will happen latter.
As far as the Zoea syndrome has been understood in the Americas with
vannamei, it may be an intracellular bacterial problem and with a very clear
cross-contamination problem.
Then the best solution is to stock the hatchery at once (all the tanks) in
the shortest time and then most (or all) of your hatchery tanks will make
it. As soon as you reach mysis and latter stages you don't have this problem
anymore.
So find a maturation hatchery that will provide you nauplii to stock in 2 or
3 days!
Eric Pinon
e-mail: epinon@ecua.net.ec
***************
COMMENTS
2 :
Some
success has been reported by utilizing a cyanophyte (Aphanizomenon
flos-aquae, AFA) at a 5% inclusion rate in the diet. There is ample
publications supporting the fact that AFA causes the immediate release and
circulation of N-K cells (natural killer). If you would like to investigate
this further I would be happy to fax you the papers that reference this or
you may read this on our website: http://www.desertlake.com
Howard
W. Newman
Desert Lake Technologies, LLC
12750 Keno Worden Road
Keno, OR 97627, USA
e-mail:
hwnewman@desertlake.com
or bshimp@aol.com
***************
COMMENTS
3:
I
think that Z2 problems have more to do with algae quality than with any
other factor. Most hatcheries find that by drying out after each cycle
they can control or eliminate Z2, but no one has ever been able to show a
good correlation between Z2 problems and any particular bacteria, virus or
toxin. Yet, when most hatcheries dry out, they also take their algae
cultures back to an agar slant or refrigerator. Then they clean the algae
section and start all over again with revitalized, clean cultures. Two or
three weeks into larval production the algae quality is taking a nose dive
and Z2 pops up.
If you can get a good way to quantify "algae quality" (color, cell
shape,
contamination, doubling time), I'll bet a strong correlation could be
established in most hatcheries with this problem.
Ed
e-mail: edscura@aol.com
***************
COMMENTS 4 :
I
think Z2 syndrome can affect animals at any stage and is a matter of how
well balanced your system and controls are. I have found that water
quality, bacteria, poor nauplii, poor feed, culture environmental conditions
and personnel can all contribute to difficulties in raising larvae. And you
always have to consider broodstock nutrition as well if you are producing
your own nauplii. There are ways to test each one of the above, not to
beyond a reasonable doubt but reasonably.
All aspects of culture need to be checked for quality, and cleanliness.
Bacterial work needs to be done on Artemia, algae, salt water supply,
freshwater supply, culture buildings and air supply and anywhere else you
can think of.
You have some general things that all hatcheries need to do to minimize the
effects of a Z2 syndrome. Sterilize your water supplies by some means,
we use chlorination using only 3 ppm because the water is so low in
dissolved organics and because we have only one reservoir and I need to turn
it around every 14 hours. Your chlorination rate depends on how long
you will have active chlorine in the water, I was once told 10 hours at low
dosages should kill most things, then back it up with bacterial plates to
make sure you are killing everything you want to.
Water lines need to be bleached at least once a week. Algae feed hoses or
lines should be bleached at daily. Artemia needs to be disinfected,
alga should be started using antibiotic plates.
Residual chlorine may be undetectable because it can be bound by organics
then released later affecting the organisms in the larvae tanks, too much
thiosulfate can also affect you animals.
You need to look at the shrimp and ask yourself if you are seeing a water
quality issue or a pathogen issue? Then take steps from there to test each
possible scenario.
David Leong
e-mail: dleong@bluecadia.com
***************
COMMENTS
5:
We
did a series of experiments using different water sources, including
synthetics and did show a water quality impact on Z2 problems. Not enough
resources available to pin down the problem, but it doesn’t appear to be
any of the things we normally test for. But it was reproducible.
Dallas
R. Weaver, PhD
Scientific Hatcheries
Huntington Beach, CA 92649, USA
e-mail: deweaver@gte.net
***************
COMMENTS 6 :
I
agree water WILL make a difference in your survivals. The point I was trying
to make is that it can be one or combinations of multiple factors
contributing to Z2 syndrome, do not settle for a print out of what your
water should and should not have, do not just listen to your managers saying
that it is the water. It is more than likely a combination of things
affecting your animals. Deformities due to water quality and due to
pathogens look different to me. When I talk about Z2 syndrome I am
referring to 40 to 90% of your larvae all dying at the same time whether it
is at Z1, Z2, or even M1.
I have seen what I believe epoxy paint oxidation affect animals, 85%
mortality at Z1 with no EDTA, technician did not to add to tanks, this was
for some reason corrected with 10ppm EDTA. Subsequent runs 50 to 60%
survival harvesting at 75 to 100 animals per liter. The reason I guessed the
tanks was because fibreglass 300L tanks stocked same day with same animals
and no EDTA did 80% to Z3.
Less than perfect water may be acceptable for sustained production. I
do remember seeing a 10 % difference between 2 different artificial salts
alone, don't remember where the hatchery water placed. This would be a
good place to start, perform a bioassay using artificial salts versus your
properly sterilized normal source of culture water and check for a
difference and make sure the results are reproducible. Then you may have
either identified one of your problems or crossed one off your list.
David Leong
e-mail: dleong@bluecadia.com
***************
COMMENTS
7:
Algae
is a prime culprit. We are so lucky here in Fiji but I don't know how long
we can keep it that way. We have bacterial and viral afflictions all around
us but so far remain clean.
We
all "whitewash" our hatcheries, clean up the whole thing and then
go back to our stock cultures of algae. A few days later, we have a problem.
I have experienced this in Australia and
East Africa. The so called "Z2" syndrome can hit you anywhere Z1,
Z2, right thru to M3. Of course sanitize the hatchery completely, but
remember to check the algae.
Alex Forbes
e-mail : docalec@connect.com.fj
***************
COMMENTS 8 :
So
many possible reasons like water quality, algae, egg quality... Give a great
attention to breeders nutrition (if maturation used) and select only the
best spawns (check eggs and nauplii). You can also try to "wash"
your nauplii in a specific tank, with a quite strong water exchange several
years before entering into larval rearing ponds.
If I remember well there are only one or two small shrimp farms in Fiji,
right ?
Michel Autrand
127 Av. de Peyre Grosse
34980 Saint Clement de Riviere, France
tel/fax (33) 4 67 67 00 12
Mobile : 06 11 92 22 67
michel.autrand@wanadoo.fr
http://www.marine-cultures.com
***************
COMMENTS 9 :
We
have all kinds of nasties around us in Fiji, but none in Fiji and it is our
aim to keep it that way. Australia, New Caledonia, Indonesia, Philippines,
they have it for the most part, yet here in Fiji, like the Seychelles many
years ago, we are disease free. With frozen imports from Thailand and live
imports, it is but a matter of time before we are subject to disease also.
Alec Forbes
e-mail: docalec@connect.com.fj
***************
COMMENTS 10 :
Here
are some more details:
-
This syndrome is recently observed in P. monodon hatcheries on the East
coast, and a few on the west coast of India.
- Normal survival rates of 70 to 50% for last few years dropped to 40 to 20%
in this cycle.
- Water treatment: 5ppm right up to 15 ppm chlorine, also some use only
micron filtration and UV.
- Algae: Both Chaetoceros and Skeletonema are equally popular.
- No remarkably different bacterial loads seen in tank waters on TCBS
plates.
- In some cases only about 20-30% tanks had extreme Zoea mortalities, while
other tanks showed normal survival.
- Some reported smaller mysis size, and low mysis survival.
- In some cases, the problem started with lower algal blooms, but persisted,
though to a lesser extent, even after the algae problem was corrected, or
new algal strains were introduced.
Anil Ghanekar
e-mail: anilghanekar@yahoo.com
***************
COMMENTS 11:
We
have not experienced anything we could call z2
syndrome, though we have had our problems and more! In conditioning
pond-reared F. indicus, we find there is a conditioning process that affects
the larval rearing success. Initially, survival from nauplius to Z1 is very
low (20-30%), then as the broodstock condition, zoea survival improves.
Two years ago, an increasingly serious bacterial problem set in in out
hatcheries and we could not get rid of it through dry-outs, sterilisation
etc. We also tried a couple of probiotics and eventually found one that
seemed to occupy the niche of our specific bacterial bug that affected us
through all stages. This was related to pink stains on the floors of the LRT
and often 90% zoea mortality in 10 hours. Such zoea would start off getting
pale and pinkish and die rapidly. After the probiotic application, the
problem basically disappeared. The carry-through has continued into this
season, though we have not been able to afford the probiotic again yet
(cannot sell last season's crop!). Without the probiotic, we have had our
first instance of pink bacterial stains and related low performance in
zoea-mysis in three years. Very subjective observation however.
As for our algae, we never "cleanup" using agar, but use the
dilution method. Having read the comments on algae as a potential source of
trouble, I am going to do a quick cleanup again. Basically, I stretch a
pasteur pipette into a capillary under a flame and draw up a small volume
from a mother culture using capillary action. I do this about 5 times,
innoculating 5 different testubes with fresh L1 (Guillard's modified/updated
F/2) medium. I then repeat this process from these tubes, so getting a
massive dilution. I repeat this again, getting another massive dilution.
Even a 4th dilution may be tried. These tubes are then left to grow. The
very low dilutions may fail to grow, but weeks later, one or two will start
to "smoke", showing algal growth. These are then checked
microscopically and used for further propagation, or put through a second
dilution process.
Additionally, we feed very healthy ("young") algae (Chaetoceros)
to our zoea and add some nutrients to the LRT to encourage this algae to
bloom in the LRT. We have fine tuned this to a routine: add the algae (100
litres) and 100ml L1 nutrients at 2pm the day before z1. This alga blooms to
about 100,000 cells per ml by the next morning. This way, the zoea encounter
healthy, exponentially growing algae.
Laurence Evans
e-mail : Laurence@amatikulu.co.za
***************
COMMENTS 12 :
I
have technical experience when I was working in Colombia. We had several
times z2 syndrome in one of our hatcheries. After following
different ideas, we found down that water quality was the source of the
problem.
We did different tests:
1.Grow shrimp with our first source of water (W1) and feed them with algae
grown in the same water.
2.Grow shrimp with water from different sources (W2) and feed them with
algae grown in the first source of water (W1).
3.Grow shrimp with water from different sources (W2) and feed them with
algae grown in different sources of water (W2).
4. Grow shrimp with water from different sources (W2), and feed with poor
quality of algae growing in different water sources (W2).
We used the same source of nauplii.
This test showed us that the problem was in our water because we got
Z2 syndrome in test number 1 and 2, but not in the test 3 and 4. We expected
the syndrome in test number 4, but this never happened, also we got the
highest survival in this test.
Now, working in USA with the environmental area, we are using plants and
algae to clean polluted water. I could understand what happened, in the
hatchery, years ago. I thought that any element in high concentration in the
water could affect the normal animal behavior, as in some plants where iron
is important for growth, but in high concentration it will be toxic.
When you have problems with algae it is because algae accumulate
some elements, which are present in high concentration in your water, and
then they will be toxic for your animal. Sometimes, bacteria, virus, and
fungi are not the first source in disease problems.
We changed our water source and some months later, we got the Z2
syndrome again, but just in two tanks, which came from different
maturation source. We have never bought animal from this maturation, and
then I ran the hatchery for 3 years. We were always working with high
density; 250 and 300 animals per liters.
Robinson Bazurto
e-mail: buhocol@hotmail.com