Prolonged transport of rainbow trout fingerlings in plastic bags: Optimization of hauling conditions based on survival and water chemistry

Breeding and seed production of rainbow trout is limited to government operated hatcheries in India, which often necessitates the transport of stock size fish to geographically distant farm units. Therefore, the present field study was carried out to derive suitable conditions for prolonged transport of rainbow trout fingerlings in plastic bags. Critical factors such as starvation period (24 vs. 72 h), loading density (13.3, 26.7 and 40 g/L), addition of salt (0, 3 and 6 g/L) and mild sedation with clove oil (0, 10, 20 and 40 μL/L) were evaluated based on fish survival and changes in total ammonia nitrogen (TAN), un-ionized ammonia (NH3-N), CO2 and pH of the transport water. The experimental fish (mean weight 4 ± 2 g and mean total length 5.5 ± 1.5 cm) were packed in plastic bags containing 6 L of stream water and 12 L of pressurized oxygen atmosphere, and transported by road in a refrigerated truck, at a constant temperature of 13 °C. The total distance covered and duration taken was 750 km and 40 h, respectively. On the basis of zero fish mortality and least adverse water quality after transport, we suggest that a starvation period of 72 h, loading density of 26.7 g/L and light sedation of fish with 40 μL/L clove oil prior to packing is suitable for transporting rainbow trout juveniles in plastic bags up to 40 h. To ascertain the benefit of adding salt to the transport medium, we need to further investigate the aspects of delayed mortality and long term fish welfare.