Sedation of smolt - SMOLTSED

Summary

The main objective of SMOLTSED was to investigate osmoregulation and performance of fish sedated over an extended period just before and during transfer to sea. In SMOLTSED, two controlled trials and a field trial were conducted. The first controlled trial was a simple experiment where we isolated the effect of sedation from other factors. In the second controlled trial, two sedatives, Aqui-S and Finquel were used. In addition, it was here intended to simulate a complete transportation to sea. In the last field trial, four well boat loadings were followed, where the fish was either sedated or not in connection with loading to the boat. The results show that sedation affects the fish stress response and to some extent osmoregulation. However, we do not have data suggesting that the effect persists long after the sedation has ceased or that sedation has a long-term negative effect on performance. We also have no data showing the opposite. However, in situations where it is expected that the fish provide great resistance, sedation can prevent the fish from getting injuries due to collisions and hard swimming activity. It is therefore advisable to cautiously sedate, and only when needed, i.e. in situations where the fish is handled a lot and where it is expected that the fish must work a lot, and to avoid repetitive and long-lasting sedation.