USE OF UV IN SHRIMP BROODSTOCK CULTURE
From: Kaywan Akhtarkhavari goldebi@ozemail.com.au
To: shrimp@yahoogroups.com
Sent: 17 October 2001
QUESTION:
Anyone with information on effects (if any) of U.V. irradiated water in
broodstock performance?
I’m working with kuruma prawns and they are not spawning. Any
particular elements in sea water to check?
Eduardo
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COMMENTS 1:
I have been looking at the role of UV treatment for inducing spawning in
abalone. I understand that UV radiations modify the water ionisation and
some people compare it to treating water with hydrogen peroxide.
I would like to better understand the principle associated with such
modification, and if possible what would be the implication on the
animal’s physiology.
Jean-Yves Mevel
Marine Science and Fisheries Center
Ministry of Agriculture and Fisheries
P.O. Box 467
113, Muscat
Sultanat of Oman
Tel: +968-607486
GSM: +968-903 75 25
e-mail: jymevel@omantel.net.om
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COMMENTS 2:
UV usually does
not affect your water chemistry or quality in a large sense. Other
sterilization processes such as chlorine or ozone will suffer a chemical
reaction with the organic and inorganic compounds contained in the water, in
a general sense affecting the chemistry of water. These changes could be
favorable like the fastest oxidation of organic molecules but it could also
cause other less expected and desirable changes.
There are a million other reasons for your shrimp not spawning. Are
they developing regular maturation at least?
Eric Pinon
e-mail: epinon@ecua.net.ec
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COMMENTS
3 :
There should
not be any effects from the UV as there is no residual
radiation.
Leland Lai
Aquafauna Bio-Marine, Inc.
e-mail :
lelandlai@aquafauna.com
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COMMENTS
4 :
Not completely
true. If there are some organics in the water, you
can induce a variety of chemical reactions with UV radiation and the
impacts of the reaction products are unknown. If you have an oxidant
like peroxide plus UV in the water, you can react with all sorts of
refractory organics in the water (Advanced Oxidation Processes --
used for industrial pollution control systems). Ozone plus UV is
really good attacking refractory organics.
In general, people have not had problems using UV, other than the
high capital and operating cost. There is not any documentation that
I have seen of detrimental impacts in aquaculture system, but there
is also very little scientifically solid documentation of real world
benefits (does killing most of the bacteria in the water really do
any good when the water goes into a system with bacterial inputs from
other sources -- feed, animals and human error or already existing --
or is it just a "feel good" treatment).
Dallas E. Weaver
Scientific Hatcheries
5542 Engineer Dr.
Huntington Beach, CA, 92649, USA
Tel: 714-890-0138
Fax: 714-890-3778
e-mail: deweaver@gte.net
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COMMENTS 5 :
That is why my
wording is "should not be any effects...."
The amount of UV to excite OH radicals from ozone will be
quite high exposure, but very few people are applying this as
a 1-2 punch (ozone + UV) primarily due to the cost.
Remember, most
using such equipment are in open systems and effective application, since
there is no perceivable residuals (for the most part as you say), is a
procedure of turning the counter back to little if any microbial or viral
counts (if the dosage is high enough).
Sure they multiply fast, but at least it’s clean going in. I agree
with you (knowing your background) that this may not be the best approach
if you can implement a truly biological filtration system. That would
probably be the best, but that may not be mainstream protocol for most
hatcheries... they are mostly looking for a quick fix-it pill to solve a
problem or a perceived problem...in many cases, incoming water that may
not be of good quality. Standard perceived and actual
"fix-it" equipment has been ozone or UV to turn the counts back
near zero
Leland Lai
e-mail : lelandlai@aquafauna.com
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COMMENTS 6:
Thanks for the
reply. In the light of the discussion, I have to include
that I add EDTA to the reservoir before it goes through the U.V.
Last year we had also unusual spawning rates, and identified possible high
levels of iron in surrounding area. That is why I am adding EDTA
before water gets into the hatchery.
On the other hand, I have heard that many hatcheries do not use UV
irradiated water for their broodstock.
Eduardo
e-mail: goldebi@ozemail.com.au
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COMMENTS 7 :
This is a good
topic! I agree with Dallas and want to add that there is a
paper describing formaldehyde formation as a by-product of aqueous solutions
of EDTA exposed to UV. I doubt this is significant in the EDTA
concentrations used in aquaculture. We routinely use 7 to 15 ppm EDTA and UV
with no deleterious effects to nauplii, or other shrimp larvae. Also, I'll
have to disagree with the concept that operation of UV is expensive,
especially when compared with the most common disinfection alternatives like
ozone, and chlorination-dechlorination.
Lorenzo Juarez
Seafarms International
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COMMENTS 8:
EDTA ties up a
lot more than iron. If you have high levels of iron
the water will contain a precipitate after aeration and 24 hr
storage. Iron and related problems get into the details of the
water system.
Dallas E. Weaver
e-mail: deweaver@gte.net
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COMMENTS 9 :
Interesting
about the formaldehyde. The concept of expensive is very
strongly context dependent. With my product in the 50$ to 100$/kg
range, I have to ask the question of whether X $ into UV will buy me
as much performance as the same dollars spent on fluidized beds or
other filtration systems. In my case, improved water quality and
the bacterial reduction that goes with water quality improvement is
better than adding UV. Your product is worth a lot more per kg.
Dallas E. Weaver
e-mail: deweaver@gte.net