The new breed of workboats addresses the needs of crew, fish and the environment, according to shipyard Nauplius Workboats. It has used progressive design to build 3514 Utility Vessel Camilla Eslea, the world’s largest delicing vessel to date.

Bridging demands of all stakeholders involved in a workboat building endeavour presents quite a challenge. Balancing cost, performance, durability, sustainability and – first and foremost – human factors including usability, safety and comfort should all be included in the equation. According to Nauplius Workboats, “progressive design” holds all the answers. By using an agile design process, plans keep getting reworked until all modelling calculations and operational simulations add up to the ultimate outcome.

Nauplius Workboats recently delivered the 3514 Utility Vessel, the world’s largest Thermolicer to date. The 35 x 14-metre vessel was built in the Netherlands and is operated by Inverlussa Marine Services. To maximise performance, the vessel is equipped with twin triple Stranda Prolog vacuum tank fish delivery systems and a twin-line bespoke Thermolicer system designed by Scale AQ. Filtration is provided by Smir using double hydro filters along with secondary belt filtration.

The Camilla Eslea has been designed with an emphasis on complete service and low-impact environmentally friendly features, in accordance with the latest regulations for aquaculture. The Camilla Eslea was delivered to Inverlussa in September and is currently in service at Mowi locations in Scotland.

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On May 3rd 2021, the pioneering 35-metre long Thermolicer was launched at Nauplius’ yard in Groningen, the Netherlands.


While aquaculture has become a key part of global food systems, it is facing parasites alike all farming, sea lice being one of them. Once contracted, it damages the skin of salmon. There are different delicing strategies, all of which have fish welfare as a top priority. Salmon is especially sensitive to stress, which has an effect on health and growth.

Sea lice only thrive in salt water. Wild salmon gets rid of the parasite by moving to sweeter waters to swim. Farmed salmon cannot do this. Delicing salmon can be done in three ways: by giving them a bath of fresh water, by mechanical delicing or by suddenly raising the water temperature. The first method is traditional, but it has many drawbacks, the main one being that it is expensive and not environmentally friendly.

The Camilla Eslea developed by Nauplius is a Thermolicer: it gives the fish a warm bath in water that is six to eight degrees Celsius warmer than the sea water is. Knowing its goal is delicing salmon, Nauplius designed and built a vessel supporting this specific delicing system. One of Inverlussa’s goals was to contribute to a better environment. So, the shipyard took into account the environment, crew needs and most of all fish welfare and came up with the following solutions.

Also read: Watch the launch of the world’s largest Thermolicer

Power generated

There are three 677-kW Mitsubishi generators in the engine room. Because sailing and delicing never happen at the same time and the required power for both sailing and delicing is almost the same, diesel-electric propulsion with generators that also power the Thermolicer is the ideal solution and at the same time saves space on board.

The ship’s main switchboard is fed by three main Stamford generators, delivering 677 ekW @ 1500 rpm each. The generators are driven by Mitsubishi S12A2(Z3) MPTAW engines. Under normal circumstances, two of these diesel generator sets are capable of supplying all power needed for either propulsion or working alongside the fish pen.

For port operations, there is a port diesel generator set, consisting of a Volvo Penta D5A-T in combination with a Stamford generator making 70 ekW. The vessel is not required to have an emergency diesel generator, but battery capacity is plentiful.

In turn, the main switchboard feeds two Veth L-drives (type VL-400si) for main propulsion, delivering 500 ekW. The bow thruster is also supplied by Veth; this VT320 thruster delivers 335 eKW. The combined power gives a cruising speed of over 10 knots and excellent manoeuvrability, either by hand steering or via the ship’s dynamic positioning (DP) system (RH Marine).

Heat is a fuel

To reduce the carbon footprint and fuel consumption, Nauplius Workboats designed a heat recovery system to generate the base load heat. It uses heat recovered from the propulsion system for the first stage of warming-up the fish treatment water, required for the Thermolicer system.

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General arrangement of the Camilla Eslea.

Integrating the work process

The oil burners are used for temperature fine-tuning only. These burners will be alternatively fuelled by processed fish oil in addition to the heat recovery system to further reduce the vessel’s carbon footprint. ‘Seen from the designer’s perspective, we believe that a closer integration between the development of the marine platform and the working systems on board will give a far better operation of the vessel,’ Gerrit Knol, founder and naval architect of Nauplius Workboats explains.

He adds: ‘Currently, the 3514 is fitted with a twin-line bespoke Thermolicer system designed by Scale AQ, all placeable thanks to our design optimising workspace. This again will reduce space consumption, fuel consumption and emissions, hence a greener operation.’

Propulsion optimising operational profile

The fish treatment system facilitates a maximum throughput of 300 tonnes of salmon per hour depending on salmon size. Due to the unique operation of this vessel, the diesel electric configuration facilitates the best economical output at lower fuel consumption compared to traditional propulsion systems. Workflow optimisation can dramatically cut operating costs and greenhouse gas emissions to
the benefit of both clients and the environment.

Further improving the vessel’s efficiency, Nauplius optimised its operational profile to take full advantage of the diesel-electric power supply and propulsion. Whether at cruising speed or working alongside the fish pen, the fully automated Power Management System ensures continued power supply against optimal load of the engines.

Knol adds: ‘We are very proud of this design. Merging all demands of specialists working together without compromises to aesthetics. The Camilla Eslea is highly reliable, giving it a very large operating window. This is achieved by applying redundancy in the propulsion system and the independent power supply to the fish treatment systems.’

Accommodating crew life design

Working in open waters is pretty demanding for crew members. That’s why addressing the “human factor” is considered a key driver for operational performance. Nauplius Workboats applies crew-centric design principles, resulting in comfortable working conditions. Both deck and cabins are designed to promote an optimal workflow.

Stronger yet, these days, those in aquaculture rightly expect more than a standard workboat. Special attention has been given to the noise levels on board. The vessel has received the highest Crew Accommodation Comfort (CAC) notation possible and is a remarkably quiet and comfortable ship. Even at a cruising speed of 10 knots, the measured noise levels on board stay below 50 dB(A) in the crew cabins and 55 dB(A) in the wheelhouse at full speed.


Nauplius Workboats and Argos Engineering have paid close attention to safety in the design. The vessel features a high bow height and freeboard of 1 metre minimum to avoid deck immersion and safe sailing, even in heavy seas. Additionally, with a beam of 14.3 metres, the vessel is extremely stable, with no need for an antiheeling system.

The vessel is diesel-electric with DP system, which ensures safe working and sailing around the ever growing fish pens.


The key aim is the provision of safe, decent space for seafarers to live and work on board. The modern accommodation area provides the necessary space and functionality to keep crews protected from the weather and sea, while also in comfort.

Camilla Eslea has been equipped with a full-size heated living space with six cabins (three double and three single cabins for nine persons in total) located above deck. Four of these rooms are en-suite thereby exceeding ILO requirements. A shower/toilet/changing/drying area with laundry facility is next to the separate galley/mess room/lounge. This setup with a high-end finish creates an attractive “home & work” atmosphere for the crew and the option of 24-hour operation.

High capacity fish treatment

The world’s largest Thermolicer draws upon the heritage of proven vessels from Nauplius’ portfolio, such as the hybrid 1907 LUV and 2712 LUV. These unique vessels with a hybrid design offer extra deck space, access to remote slipways and withstand the harsh environments of the North Sea.

The fish treatment capacity is the highest to date in respect to the vessel’s size (<500 GT, 35 metres in length). This reduces overall fuel consumption and operational costs, while increasing the vessel’s versatility. Other vessels with high capacity fish treatment systems are far larger in size. An unusually large deck area of 377 m2 gives room for the required fish treatment system components, a direct result of the previously mentioned hybrid design.

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In cooperation with E-LED Lighting, the Camilla Eslea lights the way in any condition. It has been equipped with the FLNG series, and as you can see, there is no shortage of lighting on board.

New generation oxygen generators

The layout design of the fish treatment system and its integration into the ship greatly improves fish welfare. This is maximised by the application of vacuum pumps instead of centrifugal pumps.

The next step was made by adding custom built oxygen generators. Earlier this year, Nauplius introduced the in-house designed, engineered and built oxygen generator system ensuring a minimum of stress for the salmon before passing the treatment system. The system integration ensures a low suction height of the fish, thereby reducing stress. Filtration is provided by Smir using double hydrofilters along with secondary belt filtration.

Stability and continuity

Due to its high stability, the Camilla Eslea design minimises rolling. Combined with the dynamic positioning system, this gives the vessel a very large operating window. Fuel use barely impedes on trim, thus keeping the suction height low and stable at all times. This ensures continuity and therefore aids fish welfare. Given its 35-metre size, the Camilla Eslea with its high production is still suitable for pen-to-pen work, as well as single pen operation. The position of the ballast tanks allows for little trim to occur when using fuel, adding to the positive effect of a stable and low suction height.

The high capacity of the treatment system ensures the fish will not be crowded for longer than is absolutely necessary. Future pen designs can hold up to 500 tonnes of fish; Camilla Eslea’s fish treatment capacity ensures the ability to work on these large pens, keeping the crowding period well within the maximum allowable two hours. This not only meets fish welfare expectations, but also exceeds future possibilities.

‘If you expect different results while working conditions remain the same, innovative design will prove to be an absolute gamechanger,’ says Knol. ‘Also, our commitment to retain the highest level of operational support contributes to the competitive advantage of our clients.’

Segment specific know-how

Layout, operational equipment and manoeuvrability of the Nauplius 3514 Utility Vessel all showcase in depth knowledge of the aquaculture industry. The modular approach of Nauplius Workboats results in scalable production capacity, seamless third party collaborations, bespoke aquaculture systems and systematic flexibility.

The collaboration between Inverlussa Marine Services and Nauplius has resulted in an economical, attractive and bespoke design. The vessel is built under Lloyd’s Register classification as per UK regulations and is registered in Scotland.

Picture (top): Knowing the Camilla Eslea’s goal is delicing salmon, Nauplius designed and built a vessel supporting its specific delicing system.

This article was part of SWZ|Maritime’s November 2021 fishing special and written by Signe Caminada. Not yet a subscriber? Please visit our Subscribe page.