Comp. Biochem. Physiol., 1964, Vol. 12, pp. 179 to 183. Pergamon Press Ltd. Printed in Great Britain
THE EFFECT OF TEMPERATURE AND OXYGEN ON THE
GROWTH RATE OF THE WINDERMERE CHAR
(SALVELINUS ALPINUS WILLUGHBH)
D. R. SWIFT
Freshwater Biological Association, The Ferry House, Far Sawrey,
Ambleside, Westmorland
(Received 23 January 1964)
Abstract-1. The optimum temperature for growth of Windermere char
living in a constant envii onrnent is between 12° and 16°C. At water temperatures above and below this range the growth rate is reduced.
2. The oxygen concentration in the water between the values of 50-200
per cent of the air saturation concentration has no apparent effect on the growth
rate of the fish.
INTRODUCTION
THIS work is part of an investigation of the factors which influence the growth rate
of fish. Previous work with the brown trout has established that the annual growthrate cycle of this fish is the direct result of the seasonally changing water temperatures, that this fish grows best at a water temperature of 12°C (Swift, 1961) and
that its growth rate is not influenced by the oxygen content of the water within
the range of from 50-200 per cent of the air saturation value (Swift, 1963). This
effect of temperature on the physiology of the fish must influence its geographical
distribution. While the brown trout has a very wide distribution in temperate
countries, that of the char is more limited. According to Sterba (1962) the char is
only found in Alpine Lakes, Northern Europe, Japan, Alaska, N.E. North America,
Greenland and Iceland, suggesting that this fish is confined to colder and better
oxygenated waters than the trout. If this distribution were in fact caused by the
water temperature, then one might expect this to be reflected in a lower optimum
temperature for growth for the char than for the trout. This investigation was
undertaken to see if this was, in fact, the case.
METHODS
To determine the effect of the water temperature on the growth rate of the fish
it is necessary to maintain all other external environmental factors constant. For
this investigation the fish were kept in constant environment aquaria previously
described (Swift, 1961). A day of 12 hr light and 12 hr dark was maintained
throughout the whole of this work. Each 1001. aquarium was stocked with tenyear-old hatchery-reared char, individually marked with fin clips. The fish were
fed to satiation with minced beef liver set in gelatine (Swift, 1960).
179
180
D. R. SwIFT
The fish were introduced into the aquaria in early March at the same temperature as that of the water in which they were living. The aquaria temperatures were
then adjusted 1°C per day to their working temperatures. Two aquaria were
adjusted to each of the following temperatures: 4°, 8°, 12° and 16°C. The fish
were allowed to acclimatize to these aquarium conditions for a period of 4 weeks, at
the end of which time they were anaesthetized with tricaine-methano-sulphonate,
weighed and measured. After a further period of 4 weeks in their respective temperatures the fish were again weighed and measured.
The temperatures of the 12° and of the 16°C aquaria were then adjusted to 14°
and to 18°C respectively. These four populations of fish were allowed 4 weeks to
acclimatize to their new temperatures. They were then weighed and measured
together with the two populations of fish living at 8°C and, after a further period of
4 weeks, the fish were again weighed and measured. The fish living at 8°C were
included in this second experiment to act as a control population so that the
growth rate of the fish in the two experiments could be compared. It has been
shown that the growth rate of trout living for a prolonged period in a constant
environment slowly changes (Swift, 1962).
At the end of this experiment the fish from all the aquaria were placed in a
common stock tank where they lived in water with naturally fluctuating temperature
and under naturally changing day length for 12 weeks. They were then returned
to the constant-environment aquaria in randomly selected groups of ten fish. The
water temperature of three of the aquaria was adjusted to 8°C and that of another
three aquaria to 14°C; all the aquaria had a day of 12 hr light and 12 hr dark. Of
the three aquaria at each of the two temperatures, one was stirred with air, one with
a mixture of air and oxygen and the third with a mixture of air and nitrogen. The
gas mixtures were adjusted so that the oxygen concentrations in the three aquaria
were at air saturation, 50 per cent air saturation and 200 per cent air saturation.
The oxygen content of the aquaria water was frequently checked with a Mackereth
Oxygen Probe (Mackereth, 1964).
The fish were all weighed and measured at the beginning and at the end of this
experiment which lasted for 5 weeks.
The growth rate of the fish in this work is expressed as the specific growth rate
calculated according to the formula
InL 2 —
x 100,
T2 — Ti
T being expressed in weeks.
RESULTS
The average growth rate of the fish in the different water temperatures is shown
in Table 1. The mean growth rates for the two populations at each temperature are
shown; these two means have been combined in the final calculation. In the first
experiment the fish grew best at 12° and 16°C and worst at 4°C. In the second
experiment the fish grew best at 14°C and not as well at 8° and 18°C. In order to
181
EFFECT OF TEMPERATURE AND OXYGEN ON GROWTH RATE OF WINDERMERE CHAR
TABLE 1
Temperature (°C)
4
Tank number
Average specific growth rate,
length
Mean
Average specific growth rate,
weight
Mean
1
5
14 1.4
6
3.3
12
2
3.9
3
5.1
16
7
5.1
4
5.3
8
4.6
1.4 + 0.1
5.2 5.9
3.6 + 0.2
13.6 12.8
51 + 0.2
16.5 16.3
5.0 + 0.2
18.0 16.0
5.6 + 0.5
13.2 + 04
16.4 + 0.7
17.1 + 1.0
8
14
18
Temperature (°C)
Tank number
Average specific growth rate,
length
Mean
Average specific growth rate,
weight
Mean
8
6
2
2.7 2.6
3
3.5
7
3.4
4
8
2-4 1.3
2.6 + 01
7.4 8.5
3.4 + 0.1
11-9 10.2
1.9 + 0.8
6.1 31
8.0 + 0.5
11.1 + 0.4
4.6 + 2.2
150
0
0
•
.c
50
4
8
°c
12
14
16
18
FIG. 1. The average specific growth rate of year-old char living in groups of ten
fish in constant environments at different water temperatures. The growth rates
are expressed as a percentage of the growth rate of the fish living at 8°C, the
growth rate of the fish living at 8°C being taken as 100 per cent.
182
D. R. SWIFT
compare the growth rate of the fish in the two experiments the results have been
expressed as a percentage of the growth rate of the 8°C fish, counting the growth
rate at 8°C as 100 per cent. These combined results are shown in Fig. 1. It will be
seen from this graph that the char grows best in a water temperature of between
12° and 16°C and that in water at a temperature above and below this range the
growth rate is reduced.
TABLE 2
Temperature °C
Oxygen concentration
Average specific growth rate,
length
Average specific growth rate,
weight
Temperature °C
Oxygen concentration
Average specific growth rate,
length
Average specific growth rate,
weight
8
Normal
8
50% Air
saturation
8
200% Air
1.6 + 0.1
1.6 + 04
saturation
Fl ±02
3.8 + 0.5
4.3 + 0.3
3.3 + 04
14
14
50% Air
14
200% Air
2.5 + 0.2
2.3 + 0.2
3.3 + 0.2
' 9.0 + 0.8
8.3 + 0.7
10.7 + 0.8
Normal
saturation
saturation
Table 2 shows the average growth rates for the fish living in the different oxygen
concentrations. In this experiment the fish living at 14°C grew better than did those
living at 8°C. However, there was no difference between the growth rate of the
fish living in the different oxygen concentrations at the same water temperature.
There was, however, an indication that at the higher temperature the growth
rate of the fish was increased by the higher oxygen concentration.
DISCUSSION
These results indicate that the optimum temperature for growth of the Windermere char is between 12° and 16°C and that at water temperatures above and below
this range the growth rate of the fish is reduced. This optimum temperature range
is very similar to that found for the brown trout (Swift, 1961). The lack of any
apparent effect on the growth rate by the oxygen concentrations from 50-200 per
cent of the air saturation value is also similar to the results for the brown trout
(Swift, 1963).
Friend (1959), who has studied the subspeciation in British chars, reports that
these landlocked races have probably been isolated as close inbreeding colonies for
some 10,000 years. It would seem possible, therefore, that these fish have adapted
to a higher average environmental temperature than had the migratory char from
EFFECT OF TEMPERATURE AND OXYGEN ON GROWTH RATE OF WINDERMERE CHAR 183
which they are thought to have arisen. That these migratory char appear to be
intolerant of water as warm as that inhabited by the char of Windermere is
suggested by the fact that at the present time they are no longer found south of
latitude 64°N. Therefore, until the optimum temperature for growth of the
present migratory char and of the landlocked char living north of latitude 64°N is
known, it is not possible to say what influence the physiological factor of the
optimum temperature for growth has on the present geographical distribution of the
fish.
REFERENCES
Subspeciation
in
British Charrs. Function and Taxonomic Importance.
FRIEND G. F. (1959)
Systematics Association Publication Number 3, 121-129.
MACKERETH F. J. H. (1964) An improved galvanic cell for determination of oxygen concentration in fluids. J. Sci. Instrum. 41, 38-41.
STERBA G. (1962) Freshwater Fishes of the World (Translated and revised by TUCKER D. W.).
Vista Books, London.
SWIFT D. R. (1960) An improved feed for experimental fish. Nature, Lond. 187, 1133.
SWIFT D. R. (1961) The annual growth rate cycle in brown trout (Salmo trutta Linn.) and
its cause. J. exp. Biol. 38, 595-604.
SWIFT D. R. (1962) Evidence for the absence of an endogenous growth-rate rhythm in
brown trout (Salmo trutta Linn.). Comp. Biochem. Physiol. 6, 91-93.
SWIFT D. R. (1963) Influence of oxygen concentration on growth of brown trout, Salmo
trutta L. Trans. Amer. Fish Soc. 92, 300-301.