How the first fish fared in Norwegian farmer's ocean tank

The first fish has been harvested from salmon farmer Nordlaks' semi-closed ocean tank "Storbåtsegget" (Big Boat Egg), and the experience so far has been good, the company believes.

After Nordlaks stocked the first fish in Storbåtsegget at the end of April, the initial test period has now been completed.

"We are carrying out an escalating testing of the project, and carried out a limited release in both number and duration at the end of April," Nordlaks communications and marketing head Heidi Ryste tells Fish Farming Expert's Norwegian sister site, Kyst.no.

In total, around 68,000 salmon that were already of harvestable size (average weight 5.1 kg) were transferred from the neighbouring location Brottøy to the semi-closed ocean tank. The fish were harvested at the beginning of June with a harvest weight of just over 5.5 kilograms.

No critical challenges

Storbåtsegget is Nordlaks' first semi-closed facility and represents new technology for the company. The first period has therefore been about both closely monitoring the fish and ensuring good interaction between the technical systems.

"As with all new development projects, there is much that needs to be tested and adjusted when the facility goes from completion to ordinary operation with fish," says Ryste.

The company has had to do extensive work to complete the systems and prepare the plant for production.

"After the release, attention has been focused on ensuring stable and good conditions for the fish, gathering experience and making necessary adjustments along the way."

According to Ryste, the fish have been doing well in the facility.

"It has worked as intended. There have been no critical challenges or adjustments that have been greater than we expected. Some adjustments will be made before the next stocking, but we have not made any findings that change our project plan."

Passive water replacement

An important goal of the first test period has been to investigate how the fish respond to their stay in the ocean tank, while the company has also evaluated how the technology works in practice.

Nordlaks is excited to follow one part of the concept in particular.

"The effect of the passive water exchange, which is an essential part of the concept and construction, is very exciting to observe," says Ryste.

She also points out that the project will provide more knowledge about the operation of semi-closed facilities at sea.

"On a general basis, an important goal of the Sea Tank is to develop more knowledge about biosecurity, prevention of sea lice, water quality, fish welfare and practical operations."

Smolts to be stocked in the autumn

The first test period was conducted with large fish that were only to be in the facility for a short time. The results are now being used as a basis for further testing.

"The first deployment gives us some useful experience and basic documentation to assess whether it is prudent to proceed with full-scale deployment as planned."

The next step will be to release smolt into the facility.

"The first generation of smolts we release, which according to the project plan will be released in the autumn, will give us further valuable experience with how the technology works at full scale and in a real production environment."

Considering multiple uses

Nordlaks has not yet concluded how Storbåtsegget will be used when it becomes part of the company's commercial production.

"We will use the development period to assess how the ocean tank can best be used in the commercial phase. Several alternatives may be relevant, including as a post-smolt facility or a food fish facility," says Ryste.

She says that there are a lot of exciting things happening at Nordlaks at the moment. After skipping a stocking at its Havfarm shipped-shaped semi-offshore farm, fish have been stocked again at the exposed location this week.

"We have stocked fish into Havfarmen for the first time in a year."