TABLE OF CONTENTS Pages Symposium 1 - the National Sea ...

Figure 2. Growth relationships of young sockeye salmon as a function of temperature
(Brett 1979) (data from Brett et al. 1969.)
Materials and Methods
A. Experimental Design
The experiment design was a 3 (temperatures) by 4 (feeding levels) factorial design having
two replicates. Tilapia are normally considered a strongly thermophilic genus; juveniles of
O. niloticus have a thermal preference in the 30 to 36 °C range. Previous research on O.
niloticus (Likongwe et al., 1996) and O. mossambicus, including our own in a preexperimental
trial, indicated that culture temperatures near 30° C give far superior growth
rates for juveniles than lower temperatures. To bracket what was considered the most
likely optimal growth temperature, culture temperatures of 26, 29 and 32 °C were
selected. The feeding treatments for each temperature were satiation feeding four times a
day, and 87, 73 and 60 % of the specific satiation-feeding rate for that temperature. The
fish were fed at about 4-hour intervals starting at 8 AM and ending at approximately 9
PM. Timers operated the room lights, which were on daily from 6 AM to 9 PM. Fish on a
restricted diet were fed approximate ¼ of their daily ration at each feeding. Those tanks
fed to satiation were fed for approximately an hour, at the end of that period, any excess
feed floating at the surface was collected and counted, and a corresponding number of
pellets were returned to the container for each tank. At the end of the day, the amount of
feed consumed by the tanks fed to satiation were calculated, the rates of the two replicates
for each temperature were averaged, and the feed for the fish on restricted diets was
weighted out for the following day.
B. Experimental Set-Up and Materials
The fish used for these experiments are called “Rocky Mountain White Tilapia”, although
a best guess is that they are a white inter-specific species of the genus Oreochromis,
primarily O. niloticus, O. aureus, and O. mossambicus (Hallerman 2000). This hybrid has
been selectively bred at Blue Ridge Fisheries, Martinsville, Virginia, for its color and
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