Thank you Mr. Li for an interesting paper which I enjoyed reading. It always amazes me of the amount of work done in China on ecological agriculture, organic farming and unique ideas in using wastes. I am therefore pleased that we have the opportunity to discuss your paper at this Internet Conference.

In your paper, you have two case studies comparing the use of anaerobically
digested manure and manure for fish farming
(a) in Jiangsu Province and
(b) in Taixian County.

There are a number of items in the first study in Jiangsu Province that are no clear to me.

The set up is that
(a) biogas-digester slurry (chicken manure (30-60%)+pig manure) is added
into the 913 m2 "slurry pond" (852 m3 water volume, av. depth=1.4m).
(b) chicken manure and grass are added into the 3,260 m2 "manure pond"
(6,520 m3 water volume, av. depth=2m)
(c) the fish stocking density was the same (fingerlings 0.13 kg/m3) based on the effective water body.

Comment 1:
there is an error in the calculation of the effective water body for the slurry pond.
i.e. a 913 m2 pond with 1.4 m depth would give 1,278 m3 effective water body (not 852 m3)

Then you used a fingerling stocking of 0.13 kg / m3, i.e. slurry pond would
get 110 kg fingerlings (using 852 m3 data) and the manure pond would get
847 kg of fingerlings. However, in Table 2 of your paper, stocking is
different as shown in the Table columns "Net wt" and "Size (gram)" and "Weight (kg/mu)".

Q1: what is the different in the "net wt" total and "size" total and how
are these different from the above 110 kg in slurry pond and 847 kg in manure pond ?.

1 mu (1/15ha)= 666.6 m2. and the manure pond received 126.3 kg
fingerlings/mu or 0.189 kg/m2 or 1235 kg in manure pond. All these numbers are different.

Could you check why my calculations are different from yours.

Q2: what is the standard way to present fish yield ?

regards
jacky foo
Unesco Microbial Resources Center, Stockholm