SHRIMP SIZE VARIATION
From: Tommy Chandra tchandra@bhinneka.com
To: shrimp@yahoogroups.com
Date: 4 March 2002
QUESTION:
We operate a shrimp farm (mostly P. Monodon) in North
Bali Indonesia.
Huge size variation has always been our problem. We get our PLs from
quite a lot of different hatcheries along the northern coast of East Java.
Can anyone tell us if there's any specific chemical content or mineral in
our water that could've possibly caused this size variation. During
harvest, we usually get 70% to 80% in good size, the rest are small ones.
Is this normal? Any special chemical/mineral content in seawater that we
should look out for ? Our salinity is usually quite high due to lack of
fresh water at around 25 to 30 ppt.
Tommy Chandra
North Bali – Indonesia
e-mail:
tchandra@bhinneka.com
***************
COMMENTS
1 :
One thing you could try is getting the hatcheries
to screen animals before you purchase to make them more uniform in size.
This means selecting the tank or tanks you wish to purchase and getting the
farmers to put the larvae through an appropriate sized mesh to separate out
the shrimp into 2 sizes.
The mesh cage is typically a 1 meter cube with mesh on all but the top side
and with strong aeration to help the larvae pass through. Larvae will then
need about 3 days to recover from the process (some minor necrosis is often
seen in the group that is passed through the mesh).
Then you can either purchase the large size group or the small size group
(both will show equal growth in the farm as the size difference is not
genetic, probably it is due to some larvae getting off to a better start).
This should give you more uniformity of size at harvest. If it does
not then it is possible disease or other factors are affecting the
population.
I also have a question. Shrimp prices here in Ecuador are very low and
farmers are finding it hard to make a profit, how are things working out in
Indonesia, I know that your costs are a little higher in Bali and perhaps
you are selling some on the local market. But what is the general impression
in the industry, is shrimp still a profitable business in Indonesia/Asia?
Peter Larkins
Costapac S.A.
Manta, Ecuador
593 9 748214
e-mail:
plarkins@manta.ecua.net.ec
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COMMENTS
2 :
This problem is more generally resulting of the PL's
quality. You must
check the history of the PL's in the hatchery, including the history of the
broodstock and you will probably identify some batches with problems. If
you have no control on the hatchery the best is to check the size
repartition and the gills development of the PL's when you receive them and
reject the batches with too much dispersion.
In case of wild PL, most of the case the intermediaries mixed batches from
different area. In this case, in general the PL's catch in mangrove
area are better than the ones catches on beach, because, in most of the case
they are older and so bigger. Also some fishing area could be
contaminated by heavy metal and/or pesticide and the PL's catch in these
area would be affected and at least part of the individuals will give bad
results.
Hervé Lucien-Brun
e-mail :
hlub@free.fr
***************
COMMENTS
3 :
We've never seen anyone around here doing PL
screening and I am not too sure the hatcheries would let us do that. But
there were once or twice during harvest in one or two of our ponds where we
get a pretty good uniform size shrimps. I notice this usually happen where
we have a relatively high density with harvest density of over 45 shrimps /
sq. m. But in consequence, the growth rate are usually a bit slower. I am
trying to figure out whether it's due to some chemical/mineral content in
our seawater that might be a contributing factor to this.
Despite the low price of shrimps these days, I do believe there's still
profit to make. Last week we just harvested 2 ponds at size 40 and got the
price of approx. US $ 6.1per kg. Even in Bali, our overhead I could say is
pretty much similar compared to that of other areas in Indonesia. This is
because of our location which is at the Northern part of Bali which is not
so well of compared to the Southern part where there's tourism industry.
North Bali, Indonesia
e-mail: tchandra@bhinneka.com