WATER INTAKE FOR HATCHERIES
From: Alberto Gongora-Rohde
To: shrimp@egroups.com
Sent: April 19, 2000
QUESTION:
I would like to share ideas about how to deal with estuarine waters
to achieve success from nauplii to PL.
We know "oceanic water" is the ideal water to work with...
but, in
our case, we are located within a gulf and near a mangrove outlet...
which causes our "pumped water" to have heavy metals and in
great
need of filtering.
Salinity: 22 ppt annual average, and 32 ppt three months a year.
Alberto Gongora
Gongora@racsa.co.cr
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COMMENTS 1:
I used to use estuarine water in our hatchery, quite successfully. We
now use a wellpoint with a borehole pump 6m down on the beach. This
wellpoint is at the high tide level.
To process estuarine water, we did the following:
[1] Only pump at spring high tides and while salinity was above
29ppt.
[2] Water is pumped to a series of three settling tanks. Water
siphons
passively from tank 1 to tank 3. By the time the water reaches tank
3, the floor can be seen.
[3] This water is pumped through 2 sand filters in series. The
filters
have 4 grades of sand and are easily backwashed.
[4] This water is pumped into a holding tank. When not in use this
water is recycled through the 2 sand filters.
[5] For hatchery use, this water is pumped through a diatomaceous
earth filter and then a UV filter to a storage tank for heating to 28 °
Celsius. This water then passes back through the UV to the hatchery tank.
We used this system for a couple of years and then installed a
wellpoint on the beach. We now have the water passing directly to the
heated storage tank, with only UV sterilisation.
Laurence Evans
laurence@amatikulu.co.za
************************
COMMENTS 2:
Except for a few months per year, it seems that you either recycle
the water, find another site, or buy PL's.
Dallas E. Weaver, Ph.D.
Scientific Hatcheries
5542 Engineer Dr.
Huntington Beach
CA 92649, USA
deweaver@gte.net
Tel. 714-890-0138
Fax 714-890-3778
*************************
COMMENTS 3:
I can add a little information on the use of brine to increase salinity
of hatchery water. We used brine in a freshwater prawn hatchery.
Our experience was similar to that of Dan Fegan, although the salinity of
the rearing water was less, 12 ppt.
We purchased brine with a salinity of 180 to 230 ppt from solar salt
farms. We found that 6ppt could be made up with solar salt and
6 ppt
with the brine. The use of solar salt reduced costs.
Anything below
50% brine resulted in very high mortality. The brine and salt
were
mixed with well water followed by chlorination and sand filtration.
We used a recirculating system in 5 ton round bottom tanks. After
10
days of rearing we replaced 20% of the water. Otherwise, all
rearing
procedures were standard for freshwater prawn larvae. PL
production
was 20 to 35 per l. Stage 12 was reached in about 35 days.
Charles Angell
clangell@eskimo.com
*********************
COMMENTS 4 :
A couple of things regarding this with respect to P. monodon here in
Asia. I don't know if vannamei will be the same.
We managed to get reasonable survivals using ordinary salt (NaCl) to
raise the salinity from 26ppt to 30ppt some years ago. Below this the
results were poor as the larvae seem to need a more complex salt mixture.
We did get some results in small tanks that indicated this when we used
concentrated brine from a salt farm (to raise the salinity from 16 ppt)
but the salinity came back to normal about that time so we never tested it
in production.
However, many small-scale hatcheries here in Thailand which used to
produce freshwater fish switched to shrimp by using concentrated brine
which is trucked in from coastal salt pans. There was a discussion on the
list some time ago about this. You need to use brine before the salts
start to precipitate out otherwise you get the balance all wrong.
Dan Fegan
fegan@loxinfo.co.th