Dear Julian:
Julian Chara [julian@cipav.org.co]
> In a footnote in table 2 you mentioned that adult fish occupied 62.1%
of the
> harvest in the slurry loaded pond.
>
> Does this figure consider the reproduction of tilapia?
>
> According to table 2, in the manure loaded pond the average harvest
weight
> of tilapia was 100.2 grams.
>
> What was the average weight for adult tilapia in the slurry loaded
pond and
> what is the commercial size of Tilapia in China?
>
> I understand that some of the ponds in China cannot be totally emptied.
> How do you deal with tilapia reproduction in these ponds?
>
> Could you comment about the benefits of Tilapia introduction to Chinese
aquaculture?.
Table 2 footnote indicates that the adult fish occupied 62.1% net weight
or
56.2% gross weight in slurry loaded pond. In the original table I quoted
the
adult fish plus the fingerlings equaled to the net weight in manured
loaded pond
and to the gross weight in slurry pond. I don't know why.
In slurry loaded pond Tilapia grew fast, and during the growth period,
they
produced themselves and 8,259 fingerlings were harvested with the average
weight
47 g/each. The fingerlings gained 41.4 times weight , and 821
adult gained 12.4
times weight whereas Tilapia in manure loaded pond gained only 5.3
times weight.
China have practiced cross breeding of Oreochromis niloticus + Oreochromis
aurea
to get 90% above male Tilapia, but we don not feed fingerlings with
testosterone
for sex reversal. The temperate climate does not allow tilapia to reproduce
as
quick as in tropical region.
My comments on the benefits of Tilapia introduced into China:
Tilapia has been cultured over a vast areas in China since its introduction.
It
is polycultured with Chinese carps, resulting in high unit yields of
fish
production. Tilapia culture is integrated with rice farming in rice-fish
farming
systems, which are beneficial to poor farmers in mountainous areas.
Tilapia will
become a commercially important fish in China, and there will be a
potential for
future development of tilapia culture in China.
I wrote a paper "Tilapia Culture in China", but I haven't got a chance
to publish it yet.