ammonia excretion. Regressions were tested for significance by analysis of variance. The optimal response to temperature was predicted as the upper or lower asymptote of
Ž .
the best-fitting quadratic response curve Lellis and Russell, 1990 .
3. Results
Ž .
The final mean weight and SGR at 228C were significantly higher P - 0.05 than at Ž
. 248C Table 1 . No significant differences in growth were determined among 18, 20 or
Ž
2
228C. The quadratic regression of temperature on SGR SGR s y0.031T q 1.261T y
2
. Ž .
10.884, r s 0.77 Fig. 1A predicted the optimum temperature for growth to be 218C.
The intermoult period decreased as temperature increased, with lobsters at 228C Ž
. Ž
. having a significantly lower P - 0.05 intermoult period to those at 188C Table 1 . At
Ž .
248C, the intermoult period increased again and was significantly higher P - 0.05 than at 228C. The relationship between temperature and intermoult period was described by a
Ž
2 2
. Ž quadratic regression Intermoult period s 1.134T y 48.056T q 532.99, r s 0.61
Fig. .
1B . No significant difference was detected in percentage moult increment at the four Ž
. temperatures
Table 1 . The relationship between percentage moult increment and Ž
2
temperature was described by a quadratic regression Moult increment s 0.625T y
2
. 30.55T q 433.3, r s 0.99 showing that as temperature increased, there was a reduction
Ž .
in moult increment Fig. 1C . The effects of temperature on the FCR and feed consumption are shown in Table 1
Ž .
and Fig.2. No significant differences P 0.05 in FCR or feed consumption were
detected. The response of FCR to temperature was described by a quadratic regression Ž
2 2
. FCR s 0.011T y 0.434T q 5.231, r s 0.995 , which predicted that the optimum
Ž .
temperature for feed conversion was 19.38C Fig. 2A . The response of feed consump- Ž
tion to temperature was described by a quadratic regression Feed consumptions
2 2
. Ž .
y0.0137T q 0.6125T y 4.53, r s 0.53 Fig. 2B .
Table 1 Ž
. Effect of temperature on survival, growth, feed consumption, food conversion ratio
FCR and moult
increment of post-puerulus rock lobsters, J. edwardsii Ž
. Values are expressed as mean SE . Values in the same row with same superscript are not significantly
Ž .
different P 0.05 . Temperature
188C 208C
228C 248C
a a,b
a,b b
Ž . Survival
907 698
823 517
Ž . Initial mean wt g
1.020.02 0.990.01
0.960.04 0.990.03
a,b a,b
a b
Ž . Final mean wt g
5.970.23 6.09q0.38
6.770.12 4.790.43
a,b a,b
a b
Ž . Weight gain
48614 51841
61019 38235
a,b a,b
a b
Ž .
SGR BWrday 1.920.03
1.980.07 2.130.03
1.700.78
a a
b a
Total moults 30.331.86
29.671.45 46.334.10
23.672.03 Ž .
Moult increment 86.508.50
72.001.00 63.673.68
60.003.00
a a,b
b a
Ž .
Intermoult period days 33.854.85
30.601.60 19.800.76
34.691.55 Ž
. Feed consumption BWrday
2.080.07 2.100.08
2.410.11 2.210.05
FCR 1.070.04
1.070.03 1.130.05
1.310.08
Ž . Ž .
Ž . Fig. 1. Growth of J. edwardsii versus temperature meanSE . A Specific growth rate. B Intermoult
Ž . period. C Moult increment.
Temperature affected survival of lobsters, with survival at 248C being significantly Ž
. Ž
. Ž
. lower P - 0.05 than at 188C Table 1 . There were no significant differences P 0.05
in survival at 18, 20 or 228C. Most mortalities at 248C occurred as lobsters approached the moult, whilst most mortalities at the other temperatures occurred due to cannibalism
immediately after the moult.
Ž .
As expected, body weight significantly influenced P - 0.01 oxygen consumption Ž
. Ž
. rate
M of lobsters at all temperatures Table 2 . The exponent b value of the
O
2
Ž
y1
. Log -transformed linear regressions relating oxygen consumption mgrmin
to body
10
Ž . weight g varied with the culture temperature. At 188C and 248C, b was greater than 1,
meaning that the weight-specific M increased with increasing body weight. However,
O
2
Fig. 2. Feeding, oxygen consumption rate and ammonia excretion rate of J. edwardsii versus temperature Ž
. Ž . Ž .
Ž . Ž .
meanSE . A Feed conversion ratio. B Feed consumption BWrday . C Oxygen consumption rates. Ž .
Ž .
D Total ammonia nitrogen TAN excretion rates.
at 208C and 228C, b was less than 1 and weight-specific rate decreased with increasing body weight. To take into account the oxygen consumption variation due to body
weight, the oxygen consumption data were weight-standardised at each temperature Ž
. Table 3 . The standardised oxygen consumption data were then plotted against tempera-
Ž .
ture Fig. 2C . There was a significant affect of temperature on oxygen consumption Ž
. Ž
F s 5727, P - 0.01 , which was described by a quadratic regression M
s
O
2
Table 2 Ž
y1
. Linear regressions describing the relationship between total oxygen consumption
M : mg min
, total
O
2
Ž
y1
. Ž
. ammonia excretion TAN: mg min
and body weight W: g of J. edwardsii at four temperatures
2
Ž .
Temperature 8C n
Regression model r
F P
18 19
Log M s1.515 Log
W y3.138 0.74
48.7 -
0.0001
O 10
2
20 18
Log M s 0.860 Log
W y2.597 0.80
63.9 -
0.001
O 10
2
22 16
Log M s 0.692 Log
W y2.431 0.50
12.1 -
0.004
O 10
2
24 23
Log M s1.091 Log
W y2.741 0.72
54.8 -
0.001
O 10
2
18 10
Log TANs 0.794 Log W q0.229
0.75 18.3
- 0.005
10
20 11
Log TANs 0.865 Log W q0.185
0.74 19.9
- 0.003
10
22 10
Log TANs 0.187 Log W q0.772
0.28 3.07
0.118
10
24 10
Log TANs 0.196 Log W q0.850
0.36 2.29
0.205
10
Table 3 The standardised weight-specific oxygen consumption and ammonia excretion rates of J. edwardsii at each
temperature The rate data were standardised using the regression equations describing the relationship between body
Ž .
weight and oxygen consumptionrammonia excretion Table 2 . The Q values for each temperature range
10
Ž .
28C are also shown. Temperature
M Q
TAN Q
O 10
10
2
y1 y1
y1 y1
Ž .
Ž .
Ž .
Ž .
Ž .
8C mg g
min M
mg g min
TAN
O
2
18 1.66
1.216 20
2.16 3.7
1.232 1.1
22 2.3
1.4 1.598
3.7 24
2.1 0.6
1.942 2.7
2
. y0.044T q 1.91T y 18.553, r s 1.0 . Oxygen consumption increased rapidly with
temperature up to 228C, with a decline at 248C. The Q values for oxygen consumption
10
Ž .
Ž .
decreased with increasing temperatures Table 3 , ranging from 3.7 18–208C to 0.6 Ž
. 22–248C .
Ž
y1
. The Log -transformed linear regressions relating TAN excretion mgrmin
to
10
Ž . body weight g at each temperature are shown in Table 2. The ammonia excretion rate
Ž .
was influenced by body weight at 188C and 208C P - 0.01 , but not at 228C or 248C. The ammonia excretion data were standardised as for the oxygen consumption data
Ž .
Ž .
Table 3 and then plotted against temperature Fig. 2D . Ammonia excretion increased Ž
. significantly
F s 19.14, P - 0.05 with temperature and was described by a linear Ž
2
. equation TAN s 0.127T–1.174, r s 0.91 . The Q
value for ammonia excretion was
10
Ž .
low 1.1 as the temperature increased from 188C to 208C, but was higher at the upper Ž
. temperature ranges Table 3 .
4. Discussion
