Biology Reference
In-Depth Information
20
C. At the end of each trial, all fishes in a tank were captured, euthanized,
pooled, processed, and stored as described previously.
The feed supplied was salmonid soft moist 1/32 W (Rangen, Buhl, ID) with a
proximate composition of 16.6% moisture, 48.8% crude protein, 22.3% crude fat,
7.3% ash, and 5.3% NFE. Six feeding rates of 3.0, 4.0, 5.0, 6.0, 7.0, and 8.0% of the
body weight per day (BW/d) for the first trial and 0.8, 1.6, 2.4, 3.2, 4.0, and 4.8%
BW/d for the second trial were tested in this study. Each feeding rate was assigned
randomly to four replicate tanks and the larvae were fed with automatic feeders day
and night (Cui et al.
1997
). Specific growth rates were calculated using the formula:
SGR
ΒΌ
(lnWf - lnWi
100)/
t
, where lnWf is the natural logarithm of the final
weight, lnWi is the natural logarithm of the initial weight, and
t
is the time (days)
between lnWf and lnWi. Proximate composition (moisture, crude protein, crude fat,
and ash) of the initial and final larval body samples and the commercial feed were
determined by the AOAC method (Jones
1984
). Data were subjected to one-way
analysis of variance and optimal feeding rates were determined based on specific
growth rates by the broken-line model (Robbins et al.
1979
). Statistical analyses
were conducted using SAS (SAS Institute, Cary, NC) and tested at
P
at
0.05.
Differences between treatment means were determined by Tukey's studentized
range test.
<
31.3 Results
Mortality was very low and unrelated to feeding rates. Broken-line analysis on
specific growth rates indicated that the optimum feeding rates of white sturgeon at
the 6th and 10th weeks after initiation of feeding were 6.5
0.1%
BW/d, respectively (Fig.
31.1
). Growth performances were significantly affected by
the feeding rates (Tables
31.1
and
31.2
). Final body weights, body weight increases
(BWI), and feed efficiencies showed a linear increase, a plateau, or a decrease after
the plateau with further increases of feeding rates (Tables
31.1
and
31.2
). In both
0.4 and 3.8
Fig. 31.1
Broken lines
from 53 to 59 and from 82 to 88 days posthatch
