SHRIMP
LARVAL DEFORMITY
From:
Juan Martinez postlarmar@geo.net.co
Sent:
27 December 2000
QUESTION:
We
are seeing a deformity in our hatchery which we had never seen
before. It develops in ZII, and when the larvae molts, it persists.
Only at early PL stages (PL1 - 2) the animals seem to recover, or the
deformed ones have died already. We do not have that clear yet.
When the deformity is not so severe, the animal keeps good food
consumption and good activity. This deformity is present in almost
every tank in an average of 8 - 10%, no matter the maturation where
the animals come from. There is low mortality caused by this
deformity as the capture keeps high, except in 4 tanks which were
filled in a different date and with different water. In these tanks
the problem has been extreme and the losses are high. This suggests
that the problem may come in the water.
The deformity is located at the tail. It looks like if one had
compressed the tail. In the worst cases, the uropods have
disappeared. There is no tail at all. At this point, the animal
cannot swim and basically dies.
We have checked EDTA, TREFLAN, and chlorine but they seem to be OK because
tanks with and without these products develop the same deformity.
Does anybody have a clue or have experienced something similar
recently? Is there a way to solve or mitigate it?
We have experienced contamination problems troughout the year, what
we believe is pesticides in the water, but we have had 3 very good
cycles in a row and this deformity has not been seen before in our
hatchery. Moreover, when we have had deformities in the past, the
animal stops eating and loses activity.
Juan Martinez
POST LARMAR
***************
COMMENTS
1 :
Do
you keep the parameters stable in your system? Use of ozone? Heavy metals?
Do you wash the eggs or nauplii with another product than before? Do you
have a new supplier or are these products from new batches?
From
what you write, you don’t consider the problem to be viral. Do you think
that it has been entered orally? Change of equipment or nutrients?
Antonio
E-mail: amazari@supershrimpmexico.com
***************
COMMENTS
2 :
What
Artemia and other feeds are you using? I’m asking you because it
would be good to know the results from the lab if you are carrying out the
tests on these products or even on water. If the tests of the water have not
been done, you can take a sample and send it to me and I can analyse it
here, as well as samples of other products.
Eddie Flores
Vaaf
International Corp.
E-mail: vanfk@home.com
***************
COMMENTS 3 :
Besides
the Artemia and water, you might want to check your algae. I’ve seen
similar symptoms. The pesticides might be your problem; remember that they
stay in the ground a very long time. One way to lower your list of causes it
to make sure you harvest your nauplii by the light method. Don’t harvest
any nauplii that don’t reach the harvest light within 12 min after water
becomes completely calm.
Henry San Juan
E-mail: henry_sanjuan@hotmail.com
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COMMENTS 4 :
We have
already excluded the feeds that we tried out with different diets and
Artemia and the deformities were the same. The nauplii have a diverse
origin. They come from five different maturations and in all of them the
deformity is present. We keep washing the nauplii with iodine, like we
usually do. We have traditionally checked out for the heavy metals in the
water and those are within the normal limits.
We believe
that the problem will be of chemical origin in the water. For the moment we
are carrying out the physico-chemical and microbiological analyses of the
water and the animals. As soon as we have those results, I’ll send them to
you.
What sort of
beneficial influence has ozone? I’ve read a lot about it, since I’ve
seen in past the deformities caused by the use of chlorine, probably caused
by a compound resulting from the reaction of chlorine with an organic
substance or some chemical present in the water. I’ve also heard that
ozone is efficient for the removal of pesticides, but the literature
indicates that in the case of organochlorides, for example, those are not
removed but they usually change into more toxic compounds.
Juan Fernando Martinez
E-mail: postlarmar@geo.net.co
***************
COMMENTS
5 :
One
way to see if the problem is the toxicity of the water would be to filtrate
the water with activated carbon before you fill the tanks with the larval
culture. I recommend a maximum flow-through equivalent to 100 l/min for
every cubic meter of carbon in the filter. One question: in case of severe
deformities, how does the terminal part of the digestive tract look like?
Lorenzo M. Juarez Mabarak
GMSB
Shrimp Hatchery
Summerland
Key, Fl, USA
E-mail: ljuarez@seafarmsgroup.com
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COMMENTS
6:
We’ve
been working approx. for 4 months with powdered activated carbon because the
granulated carbon requires relatively high initial inversion and it’s
difficult to determine when it’s saturated. Although the results are not
yet conclusive, we think that that has helped us considerably. Is the carbon
in powder really as efficient as the granulated carbon?
The
severe deformities are characterized by an obstruction of the intestine and
the consequent loss of feed consumption. The tail looks like a carrot, thin
at the end but with a round tip.
Juan Fernando Martinez
E-mail: postlarmar@geo.net.co
***************
COMMENTS
7:
As you all know many methods for chemical impurities
removal exist. Adsorption on activated alumina and activated carbon,
ion exchange, adsorption on greensand, chemical precipitation with ferrous
salts, ozonation, and reverse osmosis are some of the methods.
I believe that physical adsorption to activated
compounds is the most effective way in aquaculture systems for removal of
pesticides or organochlorides. I would like to hear the comments and
suggestions of the shrimp list experts familiar with this topic.
As you know, ozone is a strong oxidizing material,
capable of disinfecting bacteria and viruses. Many soluble organic compounds
and materials are oxidized by ozone to produce organics which contain polar
oxygen moieties in their structures. Ozone also oxidizes polyvalent metal
cations to higher oxidation states. Under ozonation conditions, both
oxidized organics and oxidized polyvalent cations can combine, agglomerate,
coagulate and precipitate. Ozone can oxidize many anions such as cyanide,
thiocyanate, sulfide, thiosulfate and nitrite in aqueous solution.
However, as you noted in your last posted article, the
oxidized compounds formed are many times more toxic and their removal has to
be done by an alternative method which depends greatly upon the filtration
device used. Also be aware that algae are able to withstand low
ozone residuals, but cannot survive an intensive ozone treatment.
If a post-filtration step is required to combat the
small organic molecules that can potentially react into more dangerous
substances, then I consider more prudent the use of the filtration step.
For the particular case that Juan mentions, it is known that activated
coconut carbon is especially effective in removing trace organic compounds,
such as THMs organochlorides and pesticides, because it has a high surface
area, which allows for long life and high adsorption capacity. Its
high retentivity, prevents unwanted desorption of adsorbed species.
The large fraction of micropores (< 20 Angstroms) is important for
removal of low-molecular-weight organics and for removal of trace levels of
contaminants. You could also test the incorporation of special
impregnated carbon. This is activated carbon that has been chemically
coated or treated. Impregnated carbon has been specifically formulated for
many chemical compounds that have proven to be difficult to control with
standard activated carbons as coconut carbon. Impregnated activated carbon
retains specific contaminants long enough for the chemical impregnant to
react with the contaminant and form a stable compound within the carbon,
thus eliminating the contaminant from the stream.
Eddie Flores
Vaaf
International Corp.
E-mail: vanfk@home.com
***************
COMMENTS
8:
I
have no experience with granulated carbon vs. carbon in powder. Very
important is the flow of the water through the carbon bed or the time of
contact. If you have an adequate time and the problem is toxicity, you
should see the significant difference in e.g. 10 tanks with carbon vs. 10
without carbon. We’ve observed a similar deformity, with animals lacking
the anal opening.
Lorenzo M. Juarez Mabarak
E-mail: ljuarez@seafarmsgroup.com
***************
COMMENTS 9 :
Two
causes of larval deformity are inadequate broodstock nutrition and
broodstock burnout. The former is often due to insufficient pigments (such
as astaxanthin) in the diet. This can be corrected with pigment additions
(such as paprika or astaxanthin) to the diet.
Broodstock
burnout occurs after three or four months of nauplii production by a group
of broodstock. While nauplii quantities may be satisfactory, quality is
declining. This is best corrected by replacing the exhausted broodstock with
fresh animals.
Jim
Wyban PhD
High
Health Aquaculture, Inc.
Tel/Fax:
808-982-9163
E-mail: wyban@gte.net
URL :
www.hihealthshrimp.com
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COMMENTS
10 :
If your problem was in the
water or nutritional you would see it at a much larger proportion. Even if
your nauplii come from several sources they are coming from basically the
same broodstocks. You may have a small percentage as you mentioned
(10%) which are weakers or genetically different that present the
deformities and therefore mortalities you are seeing.
My suggestion is that you do not change anything, just add 10% more
nauplii and see if you can work it out with your supplier. Also, check
with other hatcheries to see if they are seeing the same pattern or losing a
10% that they were not losing before.
Jose Bolivar Martinez
E-mail: farallon1@paranet.com
***************
COMMENTS
11:
Around 20 days ago, I
posted a message about a larval deformity I was
experiencing. I want to give an update on what happened next.
I have already harvested all my hatchery and the results are more
than satisfactory. I want to make clear that the problem is NOT
genetic. NO other local hatchery had or has reported any deformity at
all. I have experienced some environmental contamination in the past
and have implemented several managements and treatments to overcome the
situation. They have proved to be effective. It is important to point out
that NO antibiotic was used during the whole cycle.
The deformity I mentioned before was kept under 10 to 15% of the
whole population, and it disappeared during the first days of PL.
Most probably the deformed animal died. We never experienced massive deaths
and the PLs harvested passed all the physiological and stress tests required
by the farms (some of them are really extreme). The final survival rate is
in the 50% range.
Juan Fernando Martinez
E-mail: postlarmar@geo.net.co
***************
COMMENTS
12:
I
am happy to hear that your 15% deformity turned out to be nothing but a
stress on the owner.
The only problem is that you don't know what happened and therefore there is
not much gain from your experience. It may happen again. You seem
to be content with the assumption that the water may have some contaminants
and that you may have corrected it. If so, why only 15% got deformed?
At the end, my advise was to get 15% more nauplii from your supplier at no
cost like you were able to do in the past and forget about the problem.
Genetics could be a variable and you should not discard it, specially with
animals from a breeding program.
Jose Bolivar Martinez
E-mail: farallon1@paranet.com
***************
COMMENTS
13 :
I
had a similar problem like yours in 1989 with the tails of a percentage of my larvae looking like carrots (in colour and a lack of
defined telson).
They got this because our weekly caustic soda clean-out of plumbing hardware
at pH 11 was partially re-pumped back into the larvae tanks. It was not
genetic but definitely chemical/physical.
Genetically based causes of problems are extremely rare unless there is
direct genetic manipulation. I would almost go as far as to say that there
are none at present in the industry (selective breeding for traits within a
species is not direct genetic manipulation). In almost all cases they are
(controllable) external factors and pressures from human husbandry and
management that are the cause of all existing cultivation problems.
Patrick Wood
E-mail: patjwood@hotmail.com
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COMMENTS
14 :
You are partially right, I
really cannot tell you exactly what happened, but my experience so far shows
that the problem is contamination and NOT a genetic problem. I know that
genetics is an important point to consider, and this is the first one I have
considered, and discarded. NO other similar situation has been observed in
the Atlantic coast of Colombia. If genetics were the case, this or other
type of problems would arise in any of the other 14 hatcheries and even in
farms. and IT has NOT happened.
I am not happy about having contamination problems, but it is a much better
scenario than having a genetic problem. Contamination is something that
sooner or later almost everyone in this business will have to deal with, and
I am certain that I am going the right way. 5 cycles with +50% survival and
healthy animals confirm it.
Now, you know that shrimp is one of the most sensible animals on earth to
pesticides. Even at low pptr some pesticides (carbamates, pyretroids) are
lethal or sublethal. It is not possible to assert this level of
contamination through local analysis, even though I have obtained a couple
of positives for organochlorines in the ppb range, but after I monitored all
the surrounding crops and their effluents, I can tell that pesticides are
definitely the most important contaminant to consider. Moreover, more than
100 bioassays confirm my theory and discard internal or genetic problems.
When the contamination is so low and good management practices are being
accomplished, only a small % of the animals, most possible the weakest or
most sensible ones, or even NO animals at all, may be affected by this
contamination. Last year, when my problems started, I had by this month a
10-15% survival rate compared to +50% today.
The results of my PLs in the farms are at the local industry's average. When
I have poor quality PLs, I discard them as I have done in the past.
Juan Martinez
E-mail: postlarmar@geo.net.co