Next-generation near-shore salmon farm delivered with DNV class

It was an impressive sight to see at the Gemak shipyard in Turkey in summer 2025: a massive circular structure standing 30 metres tall and 72 metres in diameter, vaguely reminiscent of an ancient amphitheatre. Made of 5,000 tonnes of steel, the innovative, semi-enclosed Nordlaks HYDRA salmon farm dwarfed the people and machines around it. Loaded onto the huge semi-submersible heavy-lift carrier that was to take it to its destination in northern Norway, the unit overhung both sides of the vessel by twelve metres.

Now that HYDRA has been submerged and permanently anchored in place with only one-third of its height visible above the water line, it blends nicely into the surrounding islands against the skyline of Norway’s majestic coastal mountains.

A fully classed salmon farm

Owned and operated by Nordlaks Oppdrett AS, HYDRA is the latest addition to DNV’s list of certified marine aquaculture units since opening this new segment in the DNV portfolio of classification services. “This unit, the first of its kind with DNV class, represents a fine example of the current trend in aquaculture towards controlled, sustainable seafood production in the emerging Blue Economy,” says Per Arild Åland, Business Development Manager, Offshore Classification at DNV. “The DNV classification and aquaculture certificates ensure high standards of safety, quality, and operational integrity.”

A new solution to long-standing aquaculture challenges

HYDRA is Nordlaks’ answer to the Norwegian government’s challenge to develop technology that helps solve the environmental issues faced by salmon farming, such as tiny parasitic crustaceans. What is more, escaped farmed salmon can not only spread diseases and parasites but may also interbreed with their wild relatives, producing offspring with limited survivability.

Hydra represents a novel and inventive approach, explains Åland. “The design merges Norway’s long-standing fish farming traditions with advanced maritime technology to create a robust, large-scale concept for sustainable seafood production in an exposed marine environment.” While conventional open-pen fish farms are placed in fjords where they are sheltered from the forces of wind and waves but experience relatively little water exchange, HYDRA is intended for deployment in protected coastal waters exposed to strong currents.

Robust design with minimal environmental footprint

Engineered to withstand harsh marine conditions and minimize environmental impact, the unit is designed to withstand significant wave heights of up to 2.5 metres. It is moored permanently at a distance of approximately 250 metres from the shore, where it is able to use shore power rather than relying on diesel generators, which are on board for emergencies only. A subsea cable connects HYDRA to Norway’s eco-friendly hydropower network.

Containment system keeps sea lice out

The unit’s ring-shaped hull ensures buoyancy and forms a barrier against the surrounding ocean – while being open at the bottom. Bjarne Johansen, COO of Nordlaks, who manages the HYDRA project, explains: “We know that sea lice primarily live in the upper layers of the water column from 0 to 10 metres. As you go deeper, the population decreases rapidly. The semi-enclosed containment system of the HYDRA shields the salmon against the surrounding water down to a depth of 20 metres below the surface.”

HYDRA was originally the brainchild of a small firm specializing in fish farming solutions. After the concept had been awarded a development grant, Nordlaks acquired the inventor company in order to implement the project. NSK Ship Design, a long-standing partner, was entrusted with the engineering work.  

Innovative passive water circulation concept

HYDRA holds 86,000 cubic metres of water, and Nordlaks expects to stock the unit with up to 700,000 fish, equivalent to an annual production capacity of roughly 3,000 tonnes. The enclosed fish habitat requires a mechanism to continuously exchange water. To avoid having to operate energy-intensive water pumps, HYDRA is designed to harness the strong tidal currents in the surrounding coastal waters. Circulation is induced by a double ring of hydrofoils around the bottom. “These vertically and horizontally angled steel panels capture the current and direct it into the vessel, then upwards along the walls, and downwards in the centre in a cyclone-type motion, refreshing the water continuously,” explains Johansen.

HYDRA is currently undergoing systematic flow testing to determine whether the flow pattern predicted in computational fluid dynamics simulations will be strong enough. “If the passive circulation system doesn’t deliver the expected water exchange rate, the unit will use its water injection system to ensure a healthy living environment for the fish,” says Johansen.

Preventing fish from escaping

The bottom of the system is formed by two nets to prevent fish from escaping. The lower net is permanently attached to the hull, while the upper one, the production net, can be raised for fish crowding, harvesting and maintenance. To keep preying birds away, HYDRA has a dome-shaped roof made of tarpaulin-type material.

Unlike conventional fish farms, HYDRA is manned on a daily basis by a crew of three, encompassing an aquaculture technician, a skilled maritime technical expert and an operations manager, supported by land-based fish health and biology experts as well as production management. The fish are fed remotely.

Safety and quality assured through the Maritime Execution Model

Obtaining certification for this complex, innovative design based on the existing regulatory framework required an extensive process, so Nordlaks approached DNV about classification. “This appeared to be a more streamlined, smoother process for our design since there was a ready-to-use package available,” says Johansen. DNV worked closely with both the designer and Nordlaks, providing a comprehensive package of early-phase review, certification, marine warranty, and classification services. “We adapted our proven Maritime Execution Model, traditionally applied in shipping and offshore projects, for this aquaculture project to ensure robust safety and quality performance,” explains Åland. “This model integrates asset integrity, health and safety of personnel, and fish escape prevention, providing a structured approach to risk management and compliance.”

Robust classification for safe offshore farming

HYDRA has been assigned the classification string OI – Offshore Fish Farming Installation Posmoor NYTEK, where the NYTEK notation confirms compliance with Norwegian aquaculture integrity requirements to prevent fish escape.

“Having followed the development of this fascinating concept, it is fantastic to see it finally installed on-site ready to supply sustainable seafood,” says Torgeir Sterri, Director Offshore Classification at DNV. “DNV has been deeply involved in risk assessment, design evaluation, building surveys, and testing. It is the combined contribution from a broad range of disciplines at DNV that enabled us to perform an efficient and smooth class/certification of Nordlaks HYDRA.”

DNV’s contribution to the HYDRA project has been much appreciated by Nordlaks, says Bjarne Johansen: “DNV’s structured approach, particularly the use of the Maritime Execution Model, has given us confidence that HYDRA is designed and built to relevant standards. This collaboration has been important in bringing our vision for sustainable offshore aquaculture to life.”

A step forward in the Blue Economy

“The HYDRA concept marks a major step forward towards satisfying the world’s soaring demand for healthy protein,” Åland points out. The DNV Seafood Forecast, the fourth instalment of the Ocean’s Future to 2050 series, predicts that the share of protein demand from aquatic animals, including freshwater species, will rise from 7 per cent in 1990 to nearly 12 per cent in 2050, and that the demand for farmed finfish will increase to about 23 million tonnes globally. “With this in mind, DNV’s classification scheme for large-scale ocean fish farms, based on decades of marine and offshore experience combined with best practices established, can add significant value to the global Blue Economy in general and innovative fish farming technologies in particular,” concludes Åland.