Biology Reference
In-Depth Information
Table 31.1 Growth performances and body proximate composition of sturgeon from 53 to
59 days posthatch
Feeding rate
3.0
4.0
5.0
6.0
7.0
8.0
Final BW (g)
3.83
0.06b
4.27
0.15ab
4.46
0.09a
4.62
0.10a
4.8
0.12 a
4.74
0.20a
BWI (%)
37.5
1.74d
50.2
2.03c
56.6
1.56bc
64.0
2.45ab
69.8
2.69ab
70.9
5.57a
Moisture
0.14c
Crude fat 3.42
0.05c 3.74
0.07bc 4.02
0.17ab 4.27
0.05a 4.27
0.04a 4.38
0.09a
Initial body weights of sturgeon juveniles was 2.3
0.9 g, and body proximate compositions (%)
were: moisture 85.8
0.9, crude protein 8.4
0.6, crude fat 3.4
0.3, and ash 1.4
0.1.
Means
S.E.M. (
n ¼
4,
P
<
0.05)
84.5
0.06a
84.48
0.02ab
83.98
0.15bc
84
0.11bc
83.7
0.13c
83.6
Table 31.2 Growth performances and body proximate composition of sturgeon from 82 to
88 days posthatch
Feeding rate
0.8
1.6
2.4
3.2
4.0
4.8
Final bw (g)
13.3
0.43c
14.27
0.56bc
16.44
0.65ab
17.8
0.54a
17.27
0.43a
18.3
0.64a
BWI (%)
0.4
0.54e
9.6
1.59d
19.8
1.01c
25.8
0.53b
35.4
1.54a
36.3
1.46a
Moisture
81.7
0.18a
80.93
0.16b
80.62
0.2bc
80.1
0.13c
80.4
0.17bc
80.23
0.1bc
Crude fat
4.27
0.21d
4.85
0.12 cd
5.22
0.06bc
5.95
0.05a
5.65
0.22ab
6.16
0.03a
Initial body weights of sturgeon juveniles was 15.78
4.4 g and body proximate compositions
(%) were: moisture 83.5
0.2, crude protein 8.5
0.2, crude fat 4.4
0.2, and ash 2.3
0.
Means
S.E.M. (
n
¼
4,
P
0.05)
<
trials, body composition was also significantly affected by feeding rates. Body
moisture contents showed a general decrease, whereas body lipid contents
increased with increasing feeding rates to the optimum, and they remained constant
at feeding rates higher than the optimum. On the other hand, ash and body protein
contents were not affected by the different feeding rates.
31.4 Discussion
Very low mortality rates were observed (0.05%) in the present study as compared
with the mortality rates previously reported for younger (1-4 weeks after initiation
of feeding) and smaller (49-366 mg) white sturgeon larvae fed at suboptimum
feeding rates (Deng et al.
2003
). This could be explained by older fishes
(2.8-13.4 g) having a better tolerance of suboptimum feeding than younger and
smaller fish. As expected, we observed in both trials a significant reduction of
optimum feeding rates with increased age and body weight. The decrease of
optimal feeding rates reported between the first and second trials was in agreement
with previous investigations. In fact, white sturgeons with body weights between 30
and 100 g had an optimal feeding rate of 2% BW/d (Hung and Lutes
1987
). White
sturgeon subyearlings with body weights of 250 g had an optimal feeding rate
between 1.5 and 2% BW/d (Hung et al.
1989
), and yearling specimens with body
weights of 750 g had an optimal feeding rate of 1.3% BW/d (Hung et al.
1995
). The
decrease in body moisture and the increase in body lipid content with increasing
