World Aquaculture Singapore 2022

November 29 - December 2, 2022



Dr. Myriam Vanderzwalmen*, Dr. Kate Mintram, Dr. Tracey Jones

Compassion in World Farming

River Court, Mill Ln,

Godalming GU7 1EZ,

United Kingdom


As global aquaculture continues to increase, Re-circulating Aquaculture Systems (RAS) are being considered as a sustainable approach to meet consumer demand for seafood, including salmon. RAS systems are on-land, man-made fish farms which rely on technology to pump water in and out of tanks. They therefore relieve marine degradation issues associated with off-shore salmon farms, such as seabed disturbance, pesticide and antibiotic contamination, and disturbances to wild stocks from sea lice infections or escapes of farmed fish. However, due to the artificial nature of these systems, they could be detrimental for fish welfare.

Stocking density is an important determination of welfare. High welfare accreditation schemes and recommendations require stocking densities of between 10 and 15 kg/m3 (Soil Association, RSPCA, CIWF) for grow-out salmon, but the average for RAS systems is 80 kg/m3 (ISFA, 2015). Other potential welfare issues emerge from the reliance of RAS systems on technology, where technological failures can result in mass mortalities, poor water quality and disease. Their potentially high water (up 9000 litres per live salmon (ISFA, 2015)) and energy usage (1.3-6.1 kWh per kg of salmon (Bostock, 2018)) also calls into question the sustainability of these systems which will greatly vary depending on the sources of energy used, the type and source of water used and the location of the RAS facility. This poster will discuss the key health and welfare considerations associated with RAS for grow-out salmon with the aim to raise the profile of fish welfare within the RAS industry.


ISFA (2015) The evolution of land based Atlantic salmon farms. Available at:

Bostock, J. (2018) Review of Recirculation Aquaculture System Technologies and their Commercial Application Prepared for Highlands and Islands Enterprise. Stirling, UK. Available at: