Live transport of rainbow trout (Onchorhynchus mykiss) and subsequent live storage in market: Water quality, stress and welfare considerations

The aim of this study was to investigate the effect of live transport of rainbow trout and subsequent live storage in an outlet aquarium on water quality, animal welfare and stress. A total of 40 fish were sampled at the following steps in the process: (1) at the raceway before transport, (2) after transport (arrival at fish outlet), (3) 24 h after fish were transferred to outlet aquarium(market), and finally, (4) after 48 h storage in the aquarium. Blood samples were collected from 10 fish at each stage and the levels of plasma cortisol, electrolytes (Na+, K+, Cl-), and whole blood lactate were assessed. Twitch ability, initial pH, and temperature were assessed in white muscle. Respiration rate and swimming behavior were also assessed while the fish were kept in the outlet. Water quality (temperature, pH, dissolved oxygen, total ammonium nitrogen, total organic carbon, alkalinity and color) were assessed along with all stress measurements. Compared with fish at the farm, live transport, including effects of loading and unloading, represented the main stressor in our study. Heavy oxygen supersaturation, possibly along with elevated levels of carbon dioxide during transport contributed to this result. Despite sub-optimal water quality and excessive respiration rates, the fish in the aquarium seemed to slowly recover after transport. To reduce the effects of stress and improve animal welfare, it is suggested to minimize air exposure time and to avoid exposing the fish to supersaturated and sub-optimal levels of dissolved oxygen. Statement of relevance: In a European context, selling live salmonids in the market is unusual. In this way, the highest possible freshness can be assured. However, live transport in closed systems and the live storage in fish outlets can imply risks related to compromised animal welfare and excessive stress as well as possible mortalities. In the present MS we looked into the how present handling routines and water quality affected the fish (behavior, stress and welfare). Possible improvements of present routines are discussed. We are not familiar with other published papers covering such a value chain for salmonids. (C) 2015 Elsevier B.V. All rights reserved.