Fasting before winter transport must be extended to 5-7 days because low water temperatures drastically slow a koi's metabolism and digestion. When water temperatures fall below 10°C, intestinal motility is reduced to about 30% of its normal rate, making the standard 48-hour fast insufficient to fully evacuate the digestive tract.
Critical Risks of Inadequate Winter Fasting:
If fish are transported with undigested food in their intestines, the physical stress and motion of travel can cause the food to ferment, producing gas. This can lead to severe abdominal distension (bloating) and, in extreme cases, intestinal rupture, which is fatal.
Comprehensive Winter Transport Protocol:
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Extended Fasting with Cooling: The extended fast must be coordinated with a gradual cooling of the holding tank water—typically a decrease of 1-2°C per day—until it matches the intended transport temperature. This allows the fish's metabolism to safely adjust.
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Transport Water Preparation: The transport bag water should be treated with specific additives to mitigate cold stress. A common and effective formula includes a 0.3% concentration of non-iodized sodium chloride (salt) and a high dose of vitamin C. The salt aids in osmoregulation and reduces metabolic effort, while vitamin C is a potent anti-stress agent.
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Post-Arrival Acclimation (Quarantine): Upon arrival, koi must be placed in a dedicated, temperature-matched quarantine system. They should be kept fasted for a minimum of 72 hours to recover from transport stress. The water temperature should then be raised very slowly, no faster than 1°C per day, before offering a small amount of highly digestible food.
In essence, winter transport protocols are more stringent due to the physiological constraints of cold-blooded animals. The extended fast, combined with controlled cooling and specialized water chemistry, is essential to prevent internal injuries and ensure the fish survive the dual stresses of cold and transit.
