During the air transportation process, fish are constantly subjected to a series of stressors starting from capture at farms to packaging for air transport, the adverse water quality and crowded and over-pressurized conditions during transport. It is well known that stress leads to osmoregulatory dysfunction (Harrell& Moline 1992; Weirich, Tomasso & Smith 1992)
and causes ¢sh mortality (Tomasso et al. 1980). The addition of salt to transport water has been found to be e¡ective in reducing osmoregulatory disturbances and fish mortality in several food¢sh species (Carneiro& Urbinati 2001). Similarly, when guppies were held in saline water for 40 h, their stress resistance increased with increasing salinity to 9%, which is close to isotonic conditions (Lim et al. 2000, Fig. 5).Subsequent experiments showed that when guppies
were packed in saline water of 1%,3% or 9% and stocked in their respective salinities for recovery(with 30% daily dilution with freshwater) after ship-ment, all three treatments displayed a signi¢cantly lower cumulative mortality than the control group
at 7 days post shipment (Fig. 6).