To conduct the study, rivers near the facilities were examined using electrofishing, a scientific technique for studying fish stocks.
Photo: NORCE / Norwegian Directorate of Fisheries.
In a statement released today, the Norwegian Directorate of Fisheries said that an investigation conducted in 2024 and 2025 showed fewer findings of escaped fish from hatcheries on the West Coast of Norway, demonstrating that its focus on preventing escapes paid off.
On behalf of the Directorate, throughout this year and last, NORCE -Norwegian Research Centre AS- conducted research into escape incidents at 32 hatcheries in Rogaland and Vestland counties. The results showed that fewer escaped fish were detected in this study compared to similar surveys conducted in 2015 and 2017.
"This indicates that the regulation on technical standards for land-based aquaculture facilities for fish has been effective, and that increased focus on technical standards and escape prevention is producing results," the Norwegian Directorate of Fisheries said in the statement the study's results.
As NORCE explains in its report, to conduct the survey, rivers near the facilities were examined using electrofishing, a scientific technique for studying fish stocks.
Essential for environmental monitoring, electrofishing uses electrical pulses that temporarily stun fish so they can be captured without harm, allowing them to be measured, identified, and then released. Designed to be non-lethal, it allows fish to return to their normal state within seconds outside the electric field.
According to the NORCE study, reliable evidence of farmed fish escaping was only found in one location: the Storelvi river, near the Herand facility in the Hardanger fjord.
There, at the Herand site, nine salmon smolts were collected, and at least one additional individual was observed in the river. At the initiative of Mowi, the owner of the hatchery, the company Sporbarhet carried out genetic analyses to determine their origin.
Although the authors of the report stated that they are unaware of the specific methods used, the results of these genetic analyses confirmed that eight of the nine salmon came from Mowi.
As for the ninth individual, analyses of growth patterns, size, and appearance clearly suggest that the ninth salmon was also of aquaculture origin, although genetic analysis did not yield a clear result.
The NORCE report added that at least one additional salmon was observed, and that there could be more in a deep pool where effective electrofishing could not be carried out.
As the Norwegian Directorate of Fisheries explained in its note, electrofishing is a suitable method for demonstrating that an escape has occurred, but the absence of findings cannot be used to rule out that escape events have occurred. The NORCE study comes to the same conclusion.
"Electrofishing is well-suited for detecting escaped fish near hatcheries,but cannot be used to exclude escape events. Not all juvenile fish present in a river are detected, especially in large, fast flowing, or deep rivers. In addition, escaped juveniles remain in rivers only until smoltification, meaning detection depends on timing and fish condition," it reads.
"Absence of findings can therefore never be taken as proof that no escape occurred," the experts of the independent research institute conclude, after noting that the extent of the escape was therefore likely greater than nine individuals.
Thus, the Norwegian Directorate of Fisheries noted that, while the study revealed fewer farmed fish escaped from hatcheries, the results of its inspections showed that many facilities still have significant potential for improvement and that systematic monitoring of these facilities is necessary to further reduce the risk of escape.
Therefore, the Directorate of Fisheries emphasized that it will continue to focus on land-based aquaculture facilities. "It is important to maintain and further develop the measures that are working well today in order to prevent escapes in the future," it concluded its statement.
