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 fish mortality (Tomasso et al. 1980). The addition of salt to transport water has been found to be effective in reducing osmoregulatory disturbances
and ¢sh mortality in several foodfish 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 significantly
lower cumulative mortality than the control group at 7 days post shipment (Fig. 6).