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Q: AFRICAN FISH FARMS, STAFF OF LIFE OR CRUEL HOAX? ( Answered 5 out of 5 stars,   1 Comment )
Category: Science > Social Sciences
Asked by: mcisencraft-ga
List Price: $7.50
Posted: 15 May 2004 17:45 PDT
Expires: 14 Jun 2004 17:45 PDT
Question ID: 346964
Using the analogy of a family of 4 in the USA roughly how large would
a back yard swimming pool have to be if it was used as a fish farm to
keep the family alive? We will assume that unlimited fish food is
provided and there is no abnormal loss (Poachers,ELF type sabotages

I just saw a photo of a hardscrabble fish farm in Africa that was
supposed to feed a village of around 40 and it looked way too small to
me. I dont think the white church group putting it in had their
figures straight. Any and all info will be helpful. Thankyou

Request for Question Clarification by digsalot-ga on 16 May 2004 14:49 PDT
Since the question is rather 'general,' we would need to know about
some other variables in order to provide an answer.  For one thing,
the type of fish being raised has a lot to do with whether a pond of
given size can support a given population.  Another factor is how much
of the diet will be provided by fish and how much from other food
stuffs.  In Africa many of the fish farms raise tilapia which is a
fish that thrives in warm waters, reproduces and reaches consumable
size quite rapidly.  I don't know if that is the variety grown in the
pond you are asking about, but if it is, a fairly small pond could
feed quite a few people if the fish is to be consumed as part of a
meal rather than being the entire meal.

In fact having fish as simply part of the meal seems more reasonable
when you realize a fish farm produces much more than just fish.  Even
a small fish pond can add a great amount of food to a village diet. 
Not only is the fish eaten but the pond water is used to fertilize and
water vegetables and other crops.

Successive drought years in Malawi showed that farmers with fish ponds
were able to produce crops around the ponds while 'traditional'
farmers had no harvest.

There is also the matter of how well the pond is managed.  If it is
poorly managed with algae blooms, little cleaning, production can drop
next to nothing.  If the pond is managed well, cleaned, etc, even
without extras such as aeration, etc, it can provide food for quite a
few people when the secondary crop characteristics are added.  If the
pond is aerated, even a small pond can feed the number you indicate. 
In such a pond the fish can thrive to such a density that the surface
is in constant motion from their swimming.

We need to know more than just a "small hardscrabble fishfarm."  The
looks can be decieving.


Clarification of Question by mcisencraft-ga on 16 May 2004 18:24 PDT
CLARIFICATION Yes we can assume that the proper species (like the one
you mentioned) were used. Also there was what looked like a small
lawnmower engine hooked to a pipe so we will give them proper aeration
and operation factors.  There would be no secondary benifit factors
like fertilizer etc.

If you can just go with how large would a pond or swimming pool have
to be to produce 4 pounds of fish per day or around 1,500 per year
that would do it. Great Job by digsalot to help get this answer nailed
down. Thankyou McIsencraft.
Answered By: digsalot-ga on 16 May 2004 20:25 PDT
Rated:5 out of 5 stars
Hello there

In aerated production ponds, tilapia are usually stocked at 9,500 to
19,500 fish per hectare or 4,000 to 8000 fish per acre.  In final
grow-out production, stocking densities for 60-100 g (roughly a
quarter pound or slightly less) tilapia range from 250 to 400 fish per
cubic meter.

The estimated time to raise tilapia from egg to food-size fish ( with
food size averaging one - one and a half pounds) is highly variable,
but is usually in a range between 6 and 12 months.  This growth period
reflects offspring from standard unimproved stocks.  More improved
stocks do much better as you will find later.

So based on these rather simple figures, a half acre pond, approx 3-4
feet deep and using the lower fish population density, could produce
2000 lbs of food size fish per year, possibly twice that by using the
upper limits.

However, figures can go much higher than that.  Some of the newer
farmed breeds of tilapia reach a harvest size of 800 grams (1.75 lb.)
after a growth period of five to six months, permitting about two
harvests per year. "In on-farm trials, a new strain developed by
ICLARM and partners grew on the average 60 percent faster than present
farm breeds, and their survival rate was almost 50 percent better.
With this growth rate, three crops per year are possible." - From
World Bank - "From "Hunting" to Farming Fish - Rapid Production
Increases Are Possible"

So once again using the figures I used in my first estimate of 2000
pounds per year, with the introduction of newer breeds, the production
could go to 6000 pounds per year with three different harvests.  Or if
the upper fish populations are used, as much as 18,000 pounds per
year, feeding not only the village but providing extra to sell on the

A well managed aerated pond as small as one quarter acre could feed a
village of 4000, let alone a village of 40.  Now while that is larger
than a back yard swimming pool, it produces a lot of fish in a small

So for your figure of 1,500 pounds per year, with a half acre
producing 6000 pounds at the lower fish population level, an eighth of
an acre, well managed and aerated, would provide what you want.  Not
too much larger than that back yard swimming pool.

Search - google
Terms - fish farming, talapia farming, african fish farming

websites used in the above: - World Bank -
"From "Hunting" to Farming Fish - Rapid Production Increases Are
Possible" - "Review of Aquaculture
Development Activites in Central And West Africa"  This website gives
some of the downside of African fish farming.  The downside has little
to do with the production of the farm in terms of quantity, but with
poor management and the desire to sell the fish as a "cash crop"
rather than using it as a local food source.  That aspect of things is
beyond whether an organization establishes a fish farm for a village
which in reality can produce enough food for the village, into the
realm of education about what to do with the product after it is
created. - Tilapia Raising -
Tilapia freshwater fishpond - "The cultivation of
tilapia" - you will find some amazing production figures, some of
which deal with African fiah farms as small as one fourtieth of an
acre. - "A case has been recorded of 150 adult Tilapias producing
15,000 fry in less than four months and another case is know in which
14 fish became 14,000 in only two and a half months."

If I may clarify anything before rating the answer, please ask.


Clarification of Answer by digsalot-ga on 17 May 2004 13:22 PDT
Thank you for your kind words and the extra.  If we can be of service
in the future, we hope to see you again.

mcisencraft-ga rated this answer:5 out of 5 stars and gave an additional tip of: $1.00
What a Powerful example of how Google can work right and really do the
job. Thanks to digsalot for boiling it down to a real answer.

From: neilzero-ga on 16 May 2004 04:36 PDT
Some Europeans and Americans are accutomed to eating a pound of meat
per day, but we can do quite well nuetritionaly on an ounce of meat
per day if our diet is otherwise balanced.
 Fish farms do produce high yield from small space, but I don't recal
the numbers.  Neil

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