8097

• UCREFRP Catalog Number: 8097
• Author: American Fisheries Society.
• Title: Proceedings of the 18th Annual Meeting, Colorado - Wyoming Chapter, American Fisheries Society.
• USFW Year: 1983.
• USFW - Doc Type: March 2-3, 1983.
• Copyright Material: NO

All lots were handled identically throughout the experiment. Vital in-
formation and comments were ]ecorded on charts for each lot. Beginning fish
weight densities (.09 lbs/ft )3were the same for each lot in the half-trough
rearing space (volume = 5.3 ft). Water flows were standardized at 5 gpm
and checked weekly. A common water source (deep-bore well) with a constant
520F temperature was used for all groups. Mortalities were replaced for the
first 3 days of the experiment then recorded daily thereafter. Each lot was
weighed bi-monthly to determine growth rates and adjust feeding according
to weight gain and fish losses. Feeding rates were calculated from a modi-
fied Butterbaugh and Willoughby formula (Horak 1969).
Criteria for evaluation were growth (total weight gain and inches/day
increase), survival, and size uniformity of the final product. Total weight
gain was determined from the final total weights of each lot at experiment
end. Inches/day increase was determined from the average actual total length
measurement of 50 fish samples, subtracting beginning total lengths and
dividing the increase by number of experiment days. Uniformity was studied
from the total length measures using length-frequency distributions. The
experiment was terminated after 98 days. Statistical analysis was restricted
to comparison of average total length measurements at end of the experiment
using a student t-test and a biological significance level of 95%.

RESULTS

The experiment design kept the six lots of fish on the same diets for
the first 28 days. Therefore, results before the feed switch (Table 2) re-
flect manner of feeding differences. Survivals were approximately the same
in all lots. Total weight gains and calculated average inches/day increases
clearly show lots five and six to have the highest growth rates. Total
weight gains in these two lots were two to three times greater than the
other four lots. Calculated average inches/day increases in lots five and
six were two to four times higher than the other groups.

Table 2. Growth results before feed switch (28 days).

Lot

Manner fed

Weight gain Increase
(g) (inches/day)
146 .0010
158 .0012
174 .0015
192 .0018
376 .0049
342 .0040

% Survival

1 Hand
2 Hand
3 Auto-surface
4 Auto-surface
5 Auto-submerged
6 Auto-submerged

98.3
96.8
98.0
97.8
97.9
97.2

Final growth results do not conclusively indicate a diet preference,
whereas manner of feeding appeared to have a noticeable effect (Table 3).
Lots five and six fed by automatic feeders with submerged feed delivery sys-
tems, had the largest total weight gains, inches/day increases, and percent
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