SalMar culls 418,000 salmon fry exposed to high pH at hatchery
Closed valve prevented water reaching vital sensors
Salmon farmer SalMar had to cull more than 400,000 fry at its hatchery in Tjuin, Norway, because a closed valve meant that a sensor system couldn’t do its job.
This led to the fish being exposed to a pH level that was far too high for nearly eight hours, and to SalMar’s decision to cull the fry for welfare reasons.
In a notification of non-conformity to the Norwegian Food Safety Authority, SalMar wrote that during the day on 7 August, 418,000 fish were sorted into department “Fry 2” at Tjuin. There had been no fish in the department before.
At the end of sorting for the day, everything looked fine, but during the watch round two hours later, the on-duty operations manager noticed that the fish were displaying very unusual behaviour, wrote SalMar.
Liming system
It was quickly discovered that sensors that track the acid-alkaline (pH) balance of the water were not receiving new water for analysis due to a closed valve. The liming system, which rebalances the pH if water becomes too acidic, had then run for eight hours without receiving feedback on the correct pH in the operating water. The pH was then read and showed 10.9 (Editor’s note: pH should be neutral at around 6.2-6.8).
The liming system was stopped immediately, and a number of measures were taken to replace the water in the entire system as quickly as possible.
Irreversible damage
“Based on literature from our subject expertise and observation of the fish in department ‘Fry 2’, we decided to cull all 418,000 fish on Thursday, 8 August. This was for welfare reasons, as the extent of damage from both short-term and long-term exposure to such a high pH is irreversible,” wrote SalMar, which is the world’s second largest Atlantic salmon farmer.
The company wrote that it will now investigate the causal conditions, so it can avoid the same incident occurring again.
Fish Farming Expert’s Norwegian sister site, Kyst.no/LandbasedAQ, has asked for a comment from SalMar on the incident, but have so far not received any feedback.
