To assist in the control of breeding condition the broodstock tanks are periodically (once or twice
a year over 8–10 weeks) changed to cooler water temperatures (23–24°C) and shorter day
lengths, to simulate dry season conditions. The ‘phase-shifting’ or ‘cycling’ of temperature and light
conditions (lowering the temperature and shortening the day length of each holding tank) occurs
sequentially in the three holding systems. As one tank is lowered into ‘winter’ conditions, another
is warming up to ‘summer’ and the third is in full summer conditions and its fish are being used to
spawn. The cycling of the tanks helps provide fish in spawning condition all year round.