Robust-Smolt: impact of early life history in freshwater recirculation aquaculture systems on Atlantic salmon robustness and susceptibility to disease at sea

Project Summary


The rapid expansion of the salmon farming sector has been made possible through the adoption of new farming technologies, such as using recirculating aquaculture systems (RAS) for the early life stages of the fish. Recirculating aquaculture systems are land-based aquaculture facilities that filter, clean and reuse the water.  

Given this optimisation of growing conditions, salmon parr/smolts produced in RAS have the ability to be larger, being transferred to sea at the right time, and shortening the time needed at sea.

RAS systems have clear advantages over flow-through and freshwater loch systems, such as the ability to control the environment, collect waste and avoid external transmission of diseases and parasites. Salmon parr/smolts produced in RAS reach larger sizes, being transferred to sea earlier than ever before and shortening the time needed at sea. 

However, our knowledge of the impacts that these new rearing systems have on salmon physiology is limited. This project aims to characterise the impacts of freshwater environmental conditions – including water chemistry and temperature, but also photoperiod, nutrition, microbiome and smoltification between RAS and open water loch systems – on fish welfare, development, performance and overall health at sea.

Anticipated benefits

  • Novel scientific knowledge generated from the project of the impact of modern RAS on salmon physiology  
  • New practices to enhance farmed stock robustness and welfare  
  • Enhanced sector productivity and sustainability


  • Institute of Aquaculture, University of Stirling 
  • Marine Scotland Science 
  • University of Exeter 
  • University of Aberdeen 
  • Cefas 
  • Roslin Institute 
  • MASTS 
  • BioMar 
  • Cooke Aquaculture Ltd 
  • Pharmaq 
  • Scottish Sea Farms (SSF) 
  • Scottish Salmon Company (SSC) 
  • Mowi 
  • Grieg Seafood 
  • Salmon Scotland (formerly Scottish Salmon Producers Organisation)


The main theory tested by the project is that early life conditions in freshwater RAS affect history traits of salmon and impacts on microbiomes, immune barriers, ion regulation capacities, and robustness at sea, especially for gill pathologies and new anaemic syndrome. These impacts may also be influenced by interrelated genetic factors that can be utilised to predict high-performing fish in these farming systems. 

This project intends to generate novel scientific knowledge of the impact of modern RAS on salmon physiology leading to new practices to enhance farmed stock robustness, welfare and ultimately sector productivity and sustainability, providing new knowledge and tools to monitor and enhance farming system efficiency and reliability for fish robustness, contributing to the competitiveness and sustainability of the UK aquaculture sector. 

Discover more on the Institute of Aquaculture's project page.