Aquaculture is undergoing a transformation with the arrival of new closed aquaculture cages , systems designed to minimize environmental impact and improve fish welfare. A growing number of pilot projects and commercial solutions are demonstrating that it is possible to produce more and better fish, with fewer escapes, less disease, and much more controlled environmental management.
In this context, names like Starfish, BlueSafe, Aquatraz C2, Heimdall, and flexible closed-cage membranes are emerging , the latter being tested primarily in Norway but also expanding to other countries. These are complemented by traditional cages and hapas, which continue to play a key role in many farms, and closed containment systems from companies like Cermaq. All of this paints a picture of aquaculture moving towards a more sustainable, technologically advanced, and performance-driven model.
What are closed aquaculture cages and why are they gaining ground?
Closed cages are systems in which fish are raised in the sea or in lakes, but separated from the outside environment by a mesh structure, membrane, or watertight bag that controls the flow of water. Unlike conventional open cages, these systems allow for water filtration, flow regulation, better oxygen management, and, very importantly, a significant reduction in contact with parasites such as sea lice.
Instead of a simple hoop and a hanging net, these solutions incorporate technical membranes, internal hydraulic systems, sensors, deep water intakes , and, in many cases, specific technologies to collect and manage the sludge and waste that accumulates at the bottom of the structure. The result is a much more controlled farming environment that resembles a "tank at sea" more than a traditional cage.
This type of closed containment is particularly linked to Atlantic salmon farming , as it is a high-value species and very susceptible to problems such as sea lice (Caligus), but the technology is being adapted to other marine and freshwater species during the grow-out and post-smolt stages. Some developments have already been tested for several years, with consistent results in fish mortality, growth, and health.
In addition to the production component, many of these projects arise in response to increasingly stringent regulatory requirements . A clear example is the Canadian province of British Columbia, where the use of enclosed cages for salmon has been mandated on certain dates, accelerating the international adoption of these technologies.
Starfish and the floating deck revolution in Listafjord
Along the coast of Listafjord, in Agder County (Norway), a solution designed to attack one of the salmon farming's most serious headaches: the combination of exhausts de peces and proliferation of parasites. It is a new closed floating cage for salmon, designed as a dynamic and highly automated system.
This cage, nicknamed “Starfish ,” has a prototype approximately 20 meters in diameter that has been operating under real-world conditions since March 2021 off the coast of Flekkefjord. Behind its development is the marine equipment supplier Nekkar, which is collaborating closely with industry experts, including the well-known aquaculture company Lerøy. The objective is clear: to keep the fish in place, minimize escapes, and control marine parasites.
The key piece of the Starfish concept is a floating cover that acts as an underwater bag and, at the same time, as the top lid of the cage. This "bag" must withstand significant mechanical stress and prevent leaks. de peces and, in turn, comply with very strict environmental requirements, both in durability and recyclability and performance in the marine environment.
To address this critical issue, the Norwegian company Protan has developed a range of recyclable, floating PVC membranes under the BlueSafe brand. With over 80 years of experience in membranes and technical textiles for demanding applications such as the oil and gas industry and water storage in desert regions, Protan has adapted and improved its technology to meet the specific challenges of aquaculture.
In the specific case of Starfish, Protan has created a new membrane quality within the BlueSafe range , with exceptional properties: a symmetrical material, highly dimensionally stable, and with durability proven through intensive cyclic testing at the SINTEF research and technology institute in Norway. All of this is designed to guarantee that the cover will withstand years of operation in harsh ocean conditions.
Protan BlueSafe: development, assembly and environmental approach
Protan's work with the BlueSafe membrane for aquaculture is not a recent development. Since the early 2000s, the company has been developing membranes and systems for the transport and storage of fresh water, even in extreme environments such as the Arabian Peninsula. This same technological foundation has subsequently been applied to specific solutions for the oil and gas industry and other sectors with highly demanding requirements.
With this experience, Protan has opted for a highly customer-oriented approach: designing the covers in direct collaboration with aquaculture operators , tailoring the product to the specific requirements of each project and farming area. The idea is to leverage the producer's practical knowledge combined with the company's technical expertise to achieve optimal performance in every case.
The manufacturing and assembly of these covers takes place at Protan's plant in Nesbyen, Norway . Part of the work is done in the factory, and another part is done directly on the cages, where specialized waterproofing technicians, wearing life jackets, weld the seams using hot air and electricity. This installation method is emission-free , which is an added benefit from an environmental perspective.
During assembly, eyelets and clips are also installed to facilitate the attachment and integration of the membrane into the floating structure. The aim is for the assembly to be not only watertight and robust, but also practical to handle, maintain, and adapt to changes in operation or current regulations.
Beyond closed cages and anti-parasite skirts, BlueSafe membranes find applications in artificial kelp forests , culture tray linings, and the lining of both old and new tanks intended for juvenile fish and cleaner species. This versatility demonstrates how a single family of materials can support different sustainable aquaculture solutions.
Flexible closed cage: Serge Ferrari's proposal
Another important element in the evolution of closed cages is the flexible cage technology developed by Serge Ferrari . In this case, the fish are raised in a kind of "box" at sea, separated from the outside environment by a combination of structural mesh and a flexible membrane specially designed for aquaculture.
The prototype of this solution was tested for approximately three years in Norway , allowing its performance to be validated in a real-world environment, with waves, temperature fluctuations, and operating pressures typical of salmon farming. Starting in 2017, the company began deploying the technology internationally for other species in the grow-out phase, demonstrating that it is not a solution exclusive to salmon.
The results observed in these flexible, enclosed cages include significant reductions in mortality , the absence of parasites such as sea lice thanks to controlled incoming water, more stable oxygen levels, and a highly competitive growth rate. All of this is achieved without the need for frequent antiparasitic treatments, directly impacting costs and reducing medication use.
Regarding waste management, Serge Ferrari's system incorporates a very interesting approach: the water is filtered, and the sludge from the bottom is collected , dried, and used as organic fertilizer. In this way, a significant portion of the nutrients that were previously lost to the marine environment are recovered and reintegrated into the terrestrial production chain.
Maintaining the membrane between production cycles is relatively straightforward, with an estimated lifespan of around 10 years for the entire cage structure. Furthermore, its flexibility allows the membrane to absorb wave energy, preventing the ruptures that are more likely in rigid fiberglass or concrete structures. Based on this, Serge Ferrari has been building a global network of distributors and integrators since 2018 to bring its solution to various markets.
Aquatraz C2: new generation of large volume closed cages
Among the large-scale projects, the commitment of Lerøy Seafood Group and SalMar to the Aquatraz C2 system, developed in conjunction with Seafarming Systems, stands out. Both companies have announced a joint investment to build six units of this model, with the aim of doubling their current production volume compared to previous technologies and consolidating Norway's technological leadership in closed aquaculture.
The Aquatraz C2 inherits the experience gained from Lerøy's S1 model and SalMar's first Aquatraz cages, but takes a step forward in volume and hydraulic design. Each unit will have a capacity of 70.000 cubic meters of water and will feature six intakes located at a depth of approximately 35 meters, guaranteeing the collection of cold, clean water with very low sea lice pressure.
This strategy of drawing water from deeper layers allows for working with water that is more stable in temperature and quality , which improves fish welfare and reduces the need for treatments. The constant renewal of the internal volume helps maintain good oxygenation and allows for the controlled removal of waste.
According to current plans, the first planting de peces These Aquatraz C2 cages are planned for the first quarter of 2027, with full operations starting in 2028. Part of the structure will be manufactured in China, while the final assembly will be done in Norwegian shipyards, involving a number of local and European technology suppliers.
Lerøy and SalMar representatives emphasize that this commitment to closed-cage production is not intended to replace traditional aquaculture entirely, but rather to complement existing technologies . The aim is to provide additional solutions for sustainable growth, reduced emissions, and the ability to address increasingly complex environmental challenges on a global scale.
Heimdall by ScaleAQ: modular, low-energy enclosed cage
Another solution gaining traction is Heimdall , the first closed cage for marine aquaculture marketed by the international supplier ScaleAQ. The concept was presented at the AquaNor trade fair in Trondheim, and its first customer was Hardingsmolt, an operator with extensive experience in closed floating containment for post-smolts since 2019.
Heimdall is a 160-meter-long cage with an effective production volume of approximately 20.000 m³. The structure features a carefully designed internal hydraulic system to optimize fish performance, maintaining efficient water flow and very low energy consumption. In fact, the total volume of water inside is renewed between once and twice per hour.
Heimdall's modular design allows it to be easily adapted to different growth configurations , for both post-smolt and commercially sized fish, and even to operate in shallower waters without losing performance or compromising safety. This gives fish farmers significant flexibility when choosing locations and adjusting biomass.
The sale of the first unit comes at a particularly opportune time, coinciding with the Norwegian government's environmental flexibility program for fish farmers in the west of the country. This program allows the use of some of the allocated biomass that was suspended under the Norwegian traffic light system, provided that closed containment systems are used to reduce the environmental impact.
According to ScaleAQ, Heimdall meets all regulatory requirements and has been designed to ensure robust and profitable operation . The company's goal is to supply high-volume cages that enable efficient production, with competitive costs and a solid technical foundation that encourages producers to invest in multiple units.
Cages and hapas: the basis of many aquaculture systems
Although the conversation is increasingly focused on closed, high-tech solutions, traditional cages and ponds (hapas) remain essential in numerous aquaculture projects, both in freshwater and marine environments. These structures allow fish and other aquatic organisms to be raised in confined spaces while maintaining direct water exchange with the surrounding environment.
Conventional cages are typically enclosed mesh structures that are fixed in ponds, rivers, lakes, or protected marine areas. They are most commonly made of reinforced plastics, metal, or polyester, designed to withstand corrosion and harsh weather conditions. Their design promotes natural circulation and oxygenation, although supplementary aeration systems can be added in areas with low water exchange.
Hapas or pantènes are smaller floating cages often used for raising fry or protecting breeding fish. Their small size allows for very precise management of feeding, stocking density, and health monitoring. They are installed in both ponds and recirculating aquaculture systems, serving as a "nursery" or controlled breeding module.
In both cases, the materials are chosen to withstand long periods in water, using PVC and polyethylene or galvanized metal wires that guarantee a suitable lifespan with reasonable maintenance. The cages can be round, square, or rectangular, while the hapas are usually rectangular or cylindrical depending on the species and the production objective.
Among the main advantages of these simpler solutions are the basic environmental control, protection from predators, and increased efficiency by better managing density de peces and feeding. Thanks to this, species such as salmon, tilapia or sea bass are produced on a large scale in open or semi-closed systems, relying on hapas for critical phases such as fry rearing or reproduction.
Cermaq's closed cage system and the protection of ecosystems
Cermaq has developed its own closed-cage system with a very clear focus: protecting both farmed fish and wild populations in the coastal regions where it operates. Many of these areas have a strong presence of native and non-native communities that depend heavily on the health of the marine ecosystem.
One of the aspects Cermaq has studied for years is the relationship between sea lice (Caligus), farmed salmon, and wild fish . The company has sought to coordinate its production with local migration patterns to minimize the risk of the parasites affecting wild salmon during their journey to and from spawning grounds.
In recent years, Cermaq has incorporated closed containment solutions that allow for much stricter control of factors such as water oxygenation, temperature, and hydrodynamic flow . These parameters are monitored with advanced sensor systems, facilitating continuous monitoring of the fish's condition and early detection of any health or welfare issues.
By having this information in real time, producers can quickly adjust feeding, water flow, or oxygenation , reducing stress and, consequently, the likelihood of disease. This approach aligns with the industry's general trend toward data-driven precision aquaculture, rather than relying solely on traditional visual observation.
Cermaq's closed cage system shows how technology can align production goals with biodiversity protection and respect for coastal communities , offering a model that other companies can use as a reference for their own developments.
Operational design: wave resistance and performance in extreme conditions
Many of these new cages and enclosed systems have been designed to operate in demanding marine environments , with significant swells and, in some cases, even typhoons. There are solutions designed for lakes and the open sea that can withstand waves of up to six meters, maintaining their structural integrity and stable behavior during severe storms.
To achieve this, high-strength materials are combined with designs that distribute loads and absorb some of the wave energy . Flexible cages, for example, adapt to the movement of the water, reducing stress, while more rigid structures use reinforcements and geometries that better dissipate mechanical stress.
In addition to physical resistance, considerable attention is paid to the energy consumption associated with the hydraulic system and water exchange. Projects like Heimdall demonstrate that it is possible to completely renew the interior volume once or twice an hour with minimal energy expenditure, a key factor for long-term economic viability.
Experiences gained from large-scale farms, including tilapia projects and other species in typhoon-prone countries , provide valuable feedback on the robustness of these designs. Positive operational references from large farms and government projects help validate that the systems not only work in theory but also under challenging real-world conditions.
All this effort in design and field testing has a common goal: to ensure that closed cages can operate for many years without serious failures , reducing risks for producers, for the fish, and for the surrounding environment.
With the addition of projects like Starfish, BlueSafe, Serge Ferrari's flexible cages, Aquatraz C2, Heimdall, classic cages and hapas, and Cermaq's systems, aquaculture is building a catalog of solutions that allow for adjusting the level of enclosure, the degree of control, and investment to the needs of each region, species, and business model. This technological diversity is paving the way for more responsible and resilient production, aligned with growing environmental and social demands, without sacrificing profitability or food safety.
