Heservoir fish culture in China
353
The return rate of
a
farmed reservoir can be estimated empirically.
Fishing size is determined by the regular growth pattern, market value, plan—
ned yield and income° The minimal fishing size accepted is usually: bighead;
0.75 kg; silver carp and common carp, 0.5 kg; grass carp, 1 kg and crucian
carp,
0.25 kg. The production cycle is defined as the time from fingerlings
stocking to marketing. There are three production cycles : 1, 2 and several
years
(Fig. 3). The choice of the cycle depends on geographic conditions,
trophic level and management conditions. In China most of the high—yield
reservoirs have a 1—year cycle.
Some examples of production
At present, about 65 % of suitable reservoir water area is used for some
form of culture.
The
total yield in 1983 was 149 000 tons, or 8.1 % of the
national total freshwater fish yield. Reservoir yield vary with different
latitudes, trophic and management conditions. High yields may exceeds 1 000
kg/ha and lower yields may be 1ess than 100 kg/ha (Table 1). The national
average yield in 1983 was 113 kg/ha.
Table
1.
Fish productivity in some reservoirs in China
R
.
L
ti
Area
Yield
Statistical
eservorrs
oca
on
(ha)
(kg/ha)
period
Xianjiang
eastern China
40 000
75
1982—1984ä
Miyun
Beijing
8 000
150
1972—1980î
Shahe
eastern
China
1
373
225
1981—1984ï
Qingshan
eastern China
567
675
1969—1983ä
Nanshahe
northwest China
160
525
1968—1975ï
Xuantan
center
of China
1.70
1
265
1983—1984äï
X no
feeding or fertilization ; xx feeding and fertilization
It should be pointed out that the stocking efficiency of reservoirs is
much higher (5—15) than in intensive culture ponds (3—6).
The return
(the ratio of recapture fish of marketable size to the
ber stocked) in Qingshan reservoir illustrates the advanced level of reser—
voir fish culture in China (Table 2). The criteria used to Judge whether a
return
is good or not are: 50 %, excellent; 10—30 % good; less than 10 %,
poor.
Table 2.
Return of bighead and silver carp in Qingshan reservoir (Sifa, 1978)
-
.
First return
Second return
T
t
1
ret
rn
Stock1ng
Stock1ng3
(1+ fish)
(2+ fish)
0
ai%
u
year
(No. X 10 )
No x
10J
%
No X
103
Z
1972
782
321
41
50
6
47
1
524
777
51
55
4
56
1974
1
237
474
38
13
10
48
1975
804
310
35
9
1 1
46
1976
1
006
406
40
Mean
41
8
49
n
353
The return rate of
a
farmed reservoir can be estimated empirically.
Fishing size is determined by the regular growth pattern, market value, plan—
ned yield and income° The minimal fishing size accepted is usually: bighead;
0.75 kg; silver carp and common carp, 0.5 kg; grass carp, 1 kg and crucian
carp,
0.25 kg. The production cycle is defined as the time from fingerlings
stocking to marketing. There are three production cycles : 1, 2 and several
years
(Fig. 3). The choice of the cycle depends on geographic conditions,
trophic level and management conditions. In China most of the high—yield
reservoirs have a 1—year cycle.
Some examples of production
At present, about 65 % of suitable reservoir water area is used for some
form of culture.
The
total yield in 1983 was 149 000 tons, or 8.1 % of the
national total freshwater fish yield. Reservoir yield vary with different
latitudes, trophic and management conditions. High yields may exceeds 1 000
kg/ha and lower yields may be 1ess than 100 kg/ha (Table 1). The national
average yield in 1983 was 113 kg/ha.
Table
1.
Fish productivity in some reservoirs in China
R
.
L
ti
Area
Yield
Statistical
eservorrs
oca
on
(ha)
(kg/ha)
period
Xianjiang
eastern China
40 000
75
1982—1984ä
Miyun
Beijing
8 000
150
1972—1980î
Shahe
eastern
China
1
373
225
1981—1984ï
Qingshan
eastern China
567
675
1969—1983ä
Nanshahe
northwest China
160
525
1968—1975ï
Xuantan
center
of China
1.70
1
265
1983—1984äï
X no
feeding or fertilization ; xx feeding and fertilization
It should be pointed out that the stocking efficiency of reservoirs is
much higher (5—15) than in intensive culture ponds (3—6).
The return
(the ratio of recapture fish of marketable size to the
ber stocked) in Qingshan reservoir illustrates the advanced level of reser—
voir fish culture in China (Table 2). The criteria used to Judge whether a
return
is good or not are: 50 %, excellent; 10—30 % good; less than 10 %,
poor.
Table 2.
Return of bighead and silver carp in Qingshan reservoir (Sifa, 1978)
-
.
First return
Second return
T
t
1
ret
rn
Stock1ng
Stock1ng3
(1+ fish)
(2+ fish)
0
ai%
u
year
(No. X 10 )
No x
10J
%
No X
103
Z
1972
782
321
41
50
6
47
1
524
777
51
55
4
56
1974
1
237
474
38
13
10
48
1975
804
310
35
9
1 1
46
1976
1
006
406
40
Mean
41
8
49
n