How stressed are the smolts immediately after release?

Using a recently published analysis method, the stress level of smolt was examined 4-8 days after release.

The level of cortisol metabolites in feces was as much as ten times higher than normal immediately after exposure, and a majority of fish still had elevated stress levels 8 days after exposure. However, the analyses also showed that stress levels decreased rapidly and that the fish were significantly less stressed 8 days after exposure compared to 4 days after exposure.

The measurements confirm that the fish are significantly stressed during transport and transition from a smolt farm on land to an open facility with full alcohol content. Despite the variation between individuals, a random sample of 10 fish was sufficient to demonstrate that the stress level decreased significantly during the first 4 days after release.

The new measurement method provides precise insight into the fish's physiological status, and can be used to assess and document how well the fish were prepared for the transition from freshwater to full per mille seawater.