Aquaculture, 36 (1984) 173-177 Elsevier Science Publishers B.V., Amsterdam
173 - Printed in The Netherlands
Brief Technical Note AN ELECTRONIC CONTROLLER FOR THE AUTOMATIC DETERMINATION OF OXYGEN CONSUMPTION IN AQUATIC ANIMALS
and W. STRYDOM
Department of Zoology, University ofPort Elizabeth, Port Elizabeth 6000 (Republic ofSouth Africa) (Accepted
11 April 1983)
ABSTRACT Emmerson, W.D. and Strydom, W., 1984. An electronic controller for the automatic determination of oxygen consumption in aquatic animals. Aquaculture, 36: 173-177. A system is described which automatically controls the oxygen consumption of three aquatic animals plus a control (four-channel) for 24 h per day. The electronic system operates four three-way valves which permit water from each of four respiration chambers to flow successively past an oxygen probe for 15-min periods. This is effected by a timer consisting of four binary counters which divide the 50 Hz mains frequency down to 15-min intervals. Circuit diagrams are given.
Oxygen consumption in aquatic animals such as fish (Caulton, 1978), crabs (Aldrich, 1975; Laird and Heafner, 1976) and prawns (Kutty et al., 1971) has largely been determined manually using single (Caulton, 1978) or multiple chambers (Hart, 1980). As a result of this manual operation most work has been confined to daylight hours, ignoring night oxygen consumption. Rice and Armitage (1974) have shown that photoperiod has an effect on oxygen consumption of the crayfish Orconectes nais, while Marais et al. (1976) developed an apparatus which could automatically determine oxygen consumption in fish 24 h a day. This allowed them to show that the routine oxygen consumption in mullet varied diurnally (Marais, 1978). This has now been demonstrated in a number of aquatic animals (Cockroft, 1982; Du Preez, in press). The availability of electronic circuit hardware has now enabled control systems to be developed which are accurate, inexpensive and virtually nonmechanical, yet flexible enough to be used for a variety of aquacultural uses such as automatic monitoring of oxygen consumption and automatic feeding (Mortensen and Vahl, 1979). The system described is for an automatic
0 1984 Elsevier Science
four-channel, continuous flow oxygen consumption system, unlike the semi-closed system described by Sutcliffe et al, (1975), and is an improvement on the Marais et al. (1976) apparatus which was largely mech~ic~, !T
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Fig. Y.. General plan of controller showing power supply, valves and relays. The timer connects to the SO Hz supply while the decoder interfaces at CH, -CH, .
The four-channel electronic valve controller consists of a power supply, a clock and a decoder which interfaces with a relay bank to control four three-way valves (Fig. 1). The power supply provides the three voltages which are necessary for the operation of the controller. These are +5 V DC for the integrated circuits (W’s), +2# V DC for the four electravalves and 4 V AC at 50 Hz which is used as a clock pulse. The clock or timer section consists of four 7493 binary counters which divide the 50 Hz mains frequency down to 15-min intervals after the sine wave has been squared by two Schmidt triggers (Fig. 2). Sorensen and Vahl (1979) similarly utilised the mains frequency in making a controller
Fig. 2, Logic diagram af timer, decoder and controls.
for automatic feeding. The clock has two controls, namely a timer stopstart switch and a reset button which provides adequate control over the timer section (Fig. 2). The decoder section consists of one 7490 decade counter and the necessary gates to provide the correct decoding of four 15-min periods. Control over the decoder consists of a channel select button. Decoding takes place according to the truth table which is included for clarity (Fig. 3).
‘HI = z.rl CH2
CH3 = X.0 c*4
Fig. 3. Decoder truth table. RESULTS
The timer was found to be accurate to within 5 s per day. The system has been successfully used for the determination of oxygen consumption in shrimp (coupled with a Radiometer acid-base analyser and chart recorder), but may be used with any suitable oxygen meter and chart recorder for any aquatic animal. Responses were identical to those already described by Marais et al. (1976). ACKNOWLEDGEMENTS
Appreciation is expressed to Mrs. J. Harris for typing the text and to Dr. A. Ansell for his appraisal of the typescript. The financial support of the CSP (SANCOR) is gratefully acknowledged.
rates of fed and starved 51A: 176-183. Caulton, M.S., 1978. The effect of temperature and mass on routine metabolism in Sarotherodon (Tilapia) moeeambicus (Peters). J. Fish, Biol., 13: 196-201. Cockroft, A., 1982. Aapects of the biology of the swimming prawn Macropetaema africanue (Balss). MSc. Thesis, University of Port Elizabeth, Port Elizabeth, Republic of South Africa.
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