
A pioneering study by researchers at Dalian Ocean University in China has revealed how the swimming behaviour of fish can shape the efficiency and sustainability of recirculating aquaculture systems (RAS).
The success of these systems hinges on one key yet often underestimated factor: the fish themselves. Their swimming has a significant influence on water flow, turbulence, and energy usage within these systems.
Using computational fluid dynamics, the researchers modelled the effects of fish behaviour on tank hydrodynamics. By incorporating bionic fish models into their experiments, they observed how fish swimming upstream or in circular patterns altered water flow, disrupted vortices, and even diminished the tank’s self-cleanning efficiency.
The study highlighted that fish movement is far from a trivial variable-it is transformative. Fish swimming upstream reduced water flow velocity by as much as 16.7%, while circular swimming patterns caused an astonishing 35.4% reduction.
These changes resulted in increased turbulence, energy loss, and uneven water circulation, ultimately disturbing the delicate balance required to maintain fish welfare and efficient waste removal.
To address these challenges, the researchers proposed optimising tank designs and adjusting water inlet velocities. Their findings demonstrated that even minor changes could significantly enhance energy efficiency and create more uniform water flow, reducing stress for both the fish and the environment.
The implications of this research go well beyond engineering. It compels us to view fish not only merely as farmed commodities but as active participant in the environment. Their swimming behaviour, shaped by millions of years of evolution, provides valuable insights into how aquaculture systems can be designed to emulate natural conditions.
Lead researcher Wu and his team discovered that stable vortices-circular currents of water-are essential for maintaining clean and oxygen-rich tanks. However, fish movement often disrupts these vortices, undermining the tank’s self-cleaning capacity. By fine-tuning water flow rates and tank geometry, aquaculture designers can better balance the needs of the fish with the operational demands of modern farming.
As the world confronts growing concerns over food security and environmental sustainability, innovations such as these could redefine aquaculture as a truly sustainable industry. This research underscores the importance of understanding the interplay between biology and technology, offering a roadmap for aquaculture systems that harmonise production with ecological responsibility.