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FEB
MAY
JULY
OCT
DEC
11ME OF YEAR
Figure 1. Somatic growth rates (means and S.E.M.) of goldfish kept at 20 C
and at two photoperiods at various times of the year. A significant differ—
ence
(p<0.05; Student's t—test) between groups at the two photoperiods is
indicated by '*'.
The concentrations of serum GH were determined for each fish at the end
of the experiments on temperature and photoperiod effects on growth. Under
constant
photoperiods, warm water temperature often resulted in elevated
serum
GH levels
that corresponded to increases in growth rate (Fig. 2).
However, this response to temperature was not consistent from experiment to
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B
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A
B
D
APRIL
—_
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___
60
40
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JULY
C
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D
B
DEC
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16L
16L
8L
8L
16L
16L
8L
8L
12
20
12
20
12
20
12
20
(A)
(B)
(C)
(D)
(A)
(B)
(C)
(D)
ENWRONMENTALREŒME
Figure 2. Serum GH levels (means and S.E.M.) of goldfish kept under constant
photoperiods and temperatures at several times of the year. The results of
Duncan's multiple range test are indicated; groups with common underscoring
are
not
significantly different (p>0.05). The environmental regimes are shown
along the abscissa: 16L and 8L refer to the number of hours of light; 12 and
20 refer to water temperature (C); the letters in parentheses refer to the
gî0ups in the range test results. Sample sizes are shown above the abscissa.