Rainbow Trout - Sustainability on the menu!
by Dr. Jesper Hedegaard Clausen, Aller Aqua Group Research and Development Director
Rainbow trout farming has a long tradition in Europe and other places. The industry has alongside market demand and technological advances developed from a traditional and smaller scale production into a leading sector within the aquaculture industry and is today a frontrunner in the development of environmentally friendly and fully traceable production systems to produce healthy products for the consumers.
In this article I will focus on the recirculating systems (RAS) and their benefits, as well as the feed solutions for these highly efficient farming systems.
A typical RAS system consists of several key components, including:
Mechanical filters
Remove particles and waste from the water.
Biofilters
Convert ammonia and nitrite from fish waste into less harmful compounds, e.g. nitrate.
Oxygenation systems
Ensure sufficient oxygen content in the water.
UV and ozone treatment
Reduces bacteria and pathogens in the system
Sludge removal systems
Collect and dispose of organic waste.
If the systems are indoors, there is also the possibility to control temperature to optimize growth conditions for the fish and not being dependent on the seasonal variation.
Some of the above advantages also create new challenges for the feed suppliers to develop feed that are suitable to be used in RAS. In feed formulations normally the fish is at the center of attention and nutritional demands of the fish farmed are key. However, in RAS systems water quality and how to manage the water become very important. So, formulating more precisely what the fish can utilize as well as managing the fecal matter from the fish to ensure a fecal structure that does not cause pollution of the water in the systems become at least as important as looking after the requirements of the fish. Precision nutrition is well-known by the livestock industries and in aquaculture we are also moving towards more exact formulations. Precision nutrition (and farming) refers to advanced technology and data- driven strategies to optimize the dietary needs of poultry for maximum efficiency, health, and productivity. Often it is an approach that tailors feed formulations to the specific requirements of the fish at different growth stages, as well as considering other variables such as genetics, environmental conditions, and health status of the fish.
Besides being interesting and a more efficient use of the raw materials used for feed production, it also potentially limits negative environmental impacts to the surrounding environments. The combination of RAS and more precise formulation results in lower water consumption, with high rates of water (more than 90%) being reused, and gives better control of the production environment.
New feeding concepts and continuously building new knowledge on nutrition for RAS are essential to utilize the possibilities in the technological advances made by companies developing the systems. It would likely be a benefit if developers of RAS systems together with nutritionists developed systems together to fully utilize the synergies.
Key aspects include:
Highly digestible feed that reduces waste and improves water quality. New feeding strategies need to be controlled carefully and fully automated. This will ensure precise dosing and reduction of waste, as well as healthy fish. Optimized feed for growth without unnecessarily straining the biofilters with uneaten feed and or excess fecal matter.
As with all new and developing systems, there are also challenges with trout farming in RAS. The new systems require a lot of capital investment to get started. The high start-up costs can be a bottleneck for these new systems. The systems are more technical in nature and require technical expertise to monitor and maintain water quality and biological balance.
Furthermore, researchers are exploring alternative protein sources to replace traditional fish meal and fish oil in aquafeeds. Innovations include using plant-based proteins, insect meals, and algae, which not only reduce reliance on wild fish stocks but also contribute to more sustainable and environmentally friendly aquaculture practices. Some new raw materials also contribute to better fecal structure, which is important for the RAS systems.
Trout farming in recirculating aquaculture systems (RAS)
represents an innovative and environmentally friendly approach to fish production.The system offers a high degree of control over the farming conditions, resulting in improved growth and health. Although there are challenges associated with high investment costs and energy consumption, these are outweighed by the benefits, including reduced environmental impact and increasing demand for sustainable fishery products.
With continued technological development and improved operating methods the rainbow trout grown in RAS is likely to play an increasingly important role in the aquaculture of the future. These advancements in RAS trout feed formulations and technologies are poised to enhance the sustainability and profitability of trout farming, offering promising solutions to meet the growing global demand for fish protein.
In conclusion, consumers that are actively looking for healthy fish that are produced in a traceable and sustainable way, with a great taste and respect for the environment as well as for animal welfare should look towards rainbow trout as an excellent meal on their plate.
