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

increment. This procedure stressed the fish much less and normal feeding patterns
resumed in a matter of days. The fish were not fed the day prior to being measured. At the
termination of the experiments, the fish were taken off feed for three days prior to the
initiation of harvesting, which lasted approximately one and one half days. The tanks were
drained, and the fish were placed on ice for approximately an hour or two, to anesthetize
the fish and increase the rigor, making them easier to fillet and reducing the amount of
blood in the fillet. The fish were weighed and measured just prior to being filleted.
Results
A. Growth Rates
As noted in the introduction, the most critical information to the aquaculturist is the
maximum specific feeding and growth rates, the optimal feeding and growth rates, and the
temperature that provides the best combination of growth and feed conversion. To reduce
the data to manageable volume, it is important to first identify the treatments that provide
the optimal and maximum growth rates.
During the course of the experiments, there were relatively few moralities. Since the tanks
were left uncovered, a number of fish jumped out of the tanks during the course of the
experiment. Although the weights, lengths and location of the “leapers” were recorded,
weights could not be accurately recorded due the condition of the carcass, and the
experimental unit of origin could not be conclusively identified. To calculate feed
conversion ratios (FCRs), specific feed consumption and intermediate growth rates for
intermediate intervals, assumptions had to be made regarding the leapers and the data
mathematically manipulated to account for changes in the number of fish between
measurement intervals.
Since the fish were taken off feed the day of and one day prior to the measurements, the
experimental interval was considered to be 33 days. The last experimental interval was
only 31 days, since the fish were taken off feed 3 days prior to harvesting. The total
duration of the test was thus considered to be 130 days. Each measurement interval was
then subdivided into thirds, or an 11-day interval. The number of fish was assumed to
change evenly during the measurement interval, and thus fish lost during the experiment
were assumed to have consumed some of the feed during the measurement interval. From
there, the average daily food consumption and daily FCRs were calculated. Using the
measured weights of the fish, the daily feed consumption, and the calculated FCRs,
specific growth and feeding rates were calculated.
A summary of the overall test results is shown in Table 1. As expected, the largest growth
was observed in the three treatments that were fed to satiation. What is surprising is that
the total amount of feed consumed by fish fed to satiation was virtually identical for all
three temperature treatments. A plot of cumulative feed consumption verses time (Figure
3) illustrates this point.
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